rendered illegible by a layer of silver chloride, is molten potassium
cyanide, or a mixture of this substance with sodium or potassium
carbonate. In a short time the silver chloride is decomposed and removed
from the smooth surface of the coin. After boiling out with water,
steeping in alcohol, drying, and brushing with a soft brush, the coins
may be coated with zapon. Coins treated in this way appear to be less
brittle than those reduced by Krefting's method. More troublesome but
less dangerous, because potassium cyanide is not used, is the treatment of
silver coins with a fused mixture of potassium and sodium carbonates. In
this case the silver chloride is converted into silver carbonate, which
is then decomposed with 50% acetic acid. Further treatment by washing,
drying, and impregnation is carried out as previously described.
Silver which has become friable (p. 51) can be rendered more compact by
cautiously heating it to redness. It will however be advisable to entrust
heating and mechanical treatment of objects which are much bent to some
skilled silversmith, whose experience may prevent disaster. Silver objects
which are largely converted into friable chloride, especially if they
are much expanded, or if large portions have broken away in the process
of removing the chloride, will hardly bear any other treatment than that
of impregnation with gum-dammar solution or with paraffin wax. As silver
chloride is easily fused such articles should not be subjected to heat.
Earthy matter can often be removed with a neutral soap and warm water,
while calcareous accretions can be dissolved by a 2% solution of
hydrochloric acid. Silver which has been blackened by silver sulphide may
be laid in a warm 2% solution of potassium cyanide. All objects should be
subsequently well washed with warm water.
(_k_) Lead and Tin.
Objects of pure lead and pure tin are rare. If much oxidized they should
be washed with warm water, dried, and impregnated with a gum-dammar
solution or with paraffin wax (pp. 70 and 91). If in a good state of
preservation they may be freed from any earthy or calcareous coating
or from lead carbonate by the cautious use of very dilute nitric acid
followed by steeping in water.
Ceresole[160] cleans oxidized leaden seals with 10% acetic acid,
neutralises the acid with ammonia, and after five minutes in alcohol
coats them thinly with wax. The seals are preserved between glass dishes
(Petri dishes), the space between the dishes being filled with cement. I
employ Krefting's method for leaden medals, using either zinc and very
dilute sulphuric acid, or zinc dust and caustic soda. Occasionally the
zinc dust becomes firmly cemented by oxide to the surface of the lead,
and, if this is the case, great care must be used in removing it. The
washing process also requires care. A very efficacious method is to allow
a stream of warm distilled water, from which the dissolved air has been
driven off by boiling, to flow over the object in a porcelain dish. I now
omit any impregnation with paraffin wax, and instead recommend removal
of the water by alcohol, drying, and coating with zapon. To preserve the
specimens after treatment, more especially from the injurious action of
perspiration from the hands, they are placed between dishes of glass or
of celluloid[161].
(_l_) Gold.
Objects of pure gold usually need only be cleaned with soap and water and
a soft brush; lime may be removed by the application of a 2% solution of
hydrochloric acid. A coating of silver chloride occurring on gold which
contains a large percentage of silver may be removed by ammonia, or,
in certain cases, by the alternate use of dilute hydrochloric acid and
ammonia.
A layer of red ferric oxide (see p. 53) is of frequent occurrence upon
gold objects, and may be removed by warming the object in a stronger
solution of hydrochloric acid, but soft brushes will often serve the same
purpose. Pure gold being very soft, only the softest so-called "silver
brushes" should be used, and all pressure or bending should be avoided.
If friable the object should be carefully impregnated with a solution of
gum-dammar (p. 70).
(_m_) Glass and Enamel.
If covered with a film of dirt, or if when in a collection objects of
glass or enamel undergo any alteration, they should be washed or steeped
in lukewarm water. When dry they should be treated with pure olive oil
or poppy-seed oil, which may be diluted with benzine. The oil helps to
restore the lustre to the glass and to bring out the colour of the enamel.
When thus treated the objects should be carefully protected from dust.
A decomposition of ancient glass when deposited in a museum has been
hitherto only rarely observed, but allusion may be here made to the
so-called 'sweating' of glass which is a question of considerable
importance in Industrial-Art collections. In this case preservation is
insured by washing with distilled water, drying, and coating with zapon.
Further particulars may be obtained from the paper by Pazaurek[162].
II. Preservation of Organic Substances.
(_n_) Bones, Horns, Ivory.
Many curators dry carefully and impregnate them with a gum-dammar solution
or shellac; isinglass or glue are however preferable, for these aqueous
solutions may be used for the treatment of damp objects, which could
scarcely be dried without cracking. In order to permeate the object these
solutions must be very dilute, and are most advantageously applied at a
temperature of about 120°F. [50°C.]. The impregnation may also be effected
in rarefied air under a bell glass (p. 68). Friable bones and similar
objects which might fall to pieces in the solution during impregnation
should be bound with strips of gauze or with string before immersion; they
are easily removed when cold. To prevent the formation of mould a small
quantity of dissolved corrosive sublimate[163] is added to the glue, or
when dry after impregnation the objects may be covered with a solution
of shellac or resin. Impregnation is of very general application, and is
frequently used for the preservation of fossil and pleistocene bones.
(_o_) Leather.
At Copenhagen the method used to render leather soft and pliable is to
place it in train oil for an hour and then dry it with filter-paper.
Lanoline may also be used with success[164]. Poppy-seed oil in benzine
(p. 86) is said to produce good results, but the "Merkbuch" recommends
the preservation of leather in this condition in alcohol[165].
(_p_) Textile Fabrics, Hair.
Earth and soil may be removed by mechanical means, and, occasionally,
careful washing may be possible. The objects should be dried and
impregnated with a gum-dammar solution (p. 70), poppy-seed oil (p.
86), or a solution of india-rubber (p. 90), or they may be preserved
in alcohol (p. 159). Some textile fabrics in the Copenhagen Museum owe
their excellent state of preservation to Steffensen's treatment, i.e.
impregnation with a solution of india-rubber in turpentine with the
addition of bees'-wax.
The following account of the treatment of textile fabrics from the
Lake-Dwellings is due to Herr Heierli, of Zürich:
"The pieces as they were taken up were laid on the ground and thus
slowly allowed to dry in the air. They were then placed between
glass plates, the edges of which were pasted over with paper. Old
pieces which had been dry for a long time, and which had become
tender and friable, were laid on the ground and watered from time
to time until they were soaked through; they were then treated in
the manner already described."
Egyptian textile fabrics preserved between glass plates often deposit
a thin layer of salt on the glass, but this is easily wiped off (see
p. 155). It must first be ascertained by a previous trial in each case
whether the salt can be removed by steeping in water or in alcohol and
water.
Hair found in peat has always a dark-brown colour from impregnation with
peaty matter. The method proposed by Bille Gram[166] for restoring the
natural colour consists of repeated and alternate treatment with very
dilute alkali solution and acid at about 120°F. [50°C.]. When the liquid
ceases to show coloration the natural colour of the hair is restored.
(_q_) Feathers.
These do not require any treatment beyond protection against insects,
which is attained by immersion in an alcoholic solution of corrosive
sublimate, or by spraying with corrosive sublimate in either alcoholic or
aqueous solution. Of course the poisonous nature of corrosive sublimate
necessitates caution in its use and it should be always labelled as such.
The use of naphthalene is not always successful, and white scales of
naphthalene are apt to make their appearance; nor does finely powdered
pepper sprinkled on the feathers, either alone or mixed with finely
powdered alum, give satisfactory results.
(_r_) Papyrus.
The method of cleaning and preserving papyrus in use in the Egyptian
department of the Royal Museums at Berlin is as follows: Those pieces
which are folded together or rolled are carefully straightened, and, if
very friable, they are first placed between damp filter paper to render
them uniformly pliable. Dust and dirt are removed with soft paint-brushes,
crystals of salt which are often found[167] are picked off with forceps.
Any growths of fungus are carefully scraped off with a knife. The papyrus
thus prepared is then placed between two thick polished glass plates,
the two opposing surfaces of which are covered with a very thin layer
of vaseline. Air is frequently admitted to dry the papyrus, while the
pressure of the glass plates tends to smooth it out, and after it has been
so treated it is mounted between thin glass plates, the edges of which
are pasted over with paper covered with an oil paint.
A papyrus preserved between glass plates often shows round the edges
a whitish border about two millimetres in breadth, and on separation
the glass plates show a slight film of the same white material on the
surface which had been in contact with the papyrus. The formation of
this film, which consists chiefly of common salt and is easily wiped off,
may be prevented by previously washing the papyrus in distilled water, a
proceeding which experience has shown to be harmless. As the papyrus will
swim on the surface it should first be immersed in alcohol until soaked
through; the process of steeping is then quite simple. The thinness of
papyrus enables the steeping to be completed after 24 to 48 hours by two
changes of the water, and care must be taken lest a too prolonged steeping
should obliterate the lettering. The water assumes a yellowish or brown
tint and the papyrus becomes somewhat lighter in colour on drying. Papyrus
may also be preserved by zapon (see Appendix), but this method has no
advantage over that of mounting between glass plates.
(_s_) Wood.
To preserve adequately articles of moist wood (and they are generally in
this condition when first excavated), preliminary measures to prevent
their drying in the air must be taken immediately after they are dug
out of the earth. If found in water, as for instance articles from
pile-dwellings, they should be conveyed in water; moist objects should
be wrapped in several thicknesses of moist cloth, and the whole wrapped
in gutta-percha membrane, or in a layer of moist moss. The cracks which
arise in wooden objects which have become dried may frequently be closed
up by laying them in lukewarm water.
As the earliest attempts at preservation were probably made upon wooden
objects there is scarcely a collection in which a number of methods are
not employed. One exception only is known to me, and here, after a plaster
of Paris cast has been taken, the object is simply allowed to shrink.
The methods proposed and carried out are so different and so numerous,
especially as regards the liquid used for impregnation, and in such
variety, that it is only necessary to deal with the most important. These
may be divided into two classes, viz. dry and wet.
(1) Dry Preservation of Wood.
Moist or wet objects are placed in thin size or in a solution of isinglass
till they are impregnated, after which they are dried gradually in a
shady place. A solution of shellac, or varnish diluted with petroleum or
benzine, is then put on with a brush.
Sometimes the objects are placed directly into a mixture of varnish and
petroleum, or they are impregnated with melted paraffin. The former is
preferable as a means of impregnation if there are cracks or holes, for
the superfluous solution readily drips from the wood when it is taken out,
while paraffin sets too soon to drain out of the cracks, and thus imparts
an unnatural white appearance to the wood. Owing to the large size of the
vessels which would be otherwise required, paraffin is only useful for
small or medium-sized objects, but when making use of varnish one end of
a large object[168] may be placed in the mixture while the solution is
repeatedly poured over the object. After two or three days the opposite
end should be placed in the solution. By repeating this process every part
of the object will soon be thoroughly impregnated.
Objects of still greater size, such as a Viking's ship, can only be
preserved by painting the surface. In such cases it is advisable to begin
with dilute varnish so as to allow the impregnating solution to penetrate
as deeply as possible into the material, instead of merely forming a skin.
A solution of waterglass has in one instance been used for the
preservation of a large boat, but the result is not satisfactory.
LEINER'S METHOD[169]. The wooden articles are laid in glycerine mixed
with a small percentage of carbolic acid. The length of time during which
they remain in the glycerine depends upon their size. When taken out they
are lightly wiped and preserved without further treatment. If a growth of
mould should occur it may be washed off.
Objects thus treated retain their moist condition and should therefore be
very carefully protected from dust.
SPEERSCHNEIDER'S METHOD[170] (cp. p. 91). Small specimens are heated for
two hours in a mixture of
8 parts of rape-seed oil,
1 part of bees'-wax,
1 part of pine resin, and
2 parts of benzene.
Larger objects require a proportionately longer heating, but the mixture
must not be allowed to actually boil. The moisture rises as steam and
causes the solution to bubble. The bubbling however continues after the
moisture has been driven off; great care must therefore be taken that
the heating is not so prolonged as to cause the object to shrink. The
highly inflammable nature of the mixture renders great caution necessary,
and should it ignite, a lid, which should always be in readiness, should
be put on the vessel. After impregnation the objects are wrapped in
blotting-paper and laid in ashes for four days to prevent the access of
air. The aim is doubtless to insure thorough absorption of the superfluous
liquid which remains upon the object, which exposure to air would prevent
by causing the mixture to set too rapidly. The same mixture can be used
repeatedly, but each time two-thirds of the original quantity of benzene
must be added.
HERBST'S METHOD[171]. The moist objects are boiled in a saturated solution
of alum for two hours (hot water dissolves about 3-1/2 times its weight of
alum), but if they are of some thickness the time must be proportionately
longer. They are then taken out, and when the alum in crystallizing has
made them more or less firm, the crystals adhering to the surface are
washed off with warm water.
When thoroughly dry the wood is brushed over with hot linseed oil, which
operation is repeated until no more oil is absorbed. A final thin coating
of varnish or shellac is then given. According to Steffensen, the method
followed at Copenhagen is to lay the objects in warm thin size for a
quarter of an hour after impregnation with alum. This alum-method is there
used for objects of oak, although the "Merkbuch" (p. 60) states that only
the varnish-petroleum mixture should be used for impregnating this class
of object.
(2) Preservation of Wooden Objects in Liquids.
The expense entailed by this method renders it applicable only to articles
of small size.
The preservation of small objects in a flat vessel, the bottom of which
is covered with glycerine, has the disadvantage that glycerine extracts
organic substances and thus assumes a brown colour. If glycerine is
used the object should undergo a thorough preliminary steeping, and
the glycerine should be renewed until it remains colourless. Closed
cylinders filled with glycerine or a mixture of glycerine and water are
not convenient because wood nearly always floats in the liquid. This may
be remedied however by the addition of alcohol.
JENNER'S METHOD[172]. When the objects have been thoroughly cleaned with
water, pure alcohol, diluted with water until the specific gravity at
54°F. [12·5°C.] reaches 0·96, is poured over them. After six or eight
weeks the alcohol is poured off and replaced by fresh alcohol of the same
specific gravity. This alcohol is examined in a year's time, and should
always show a specific gravity of 0·96. The alcohol which has been poured
off may be filtered, and if necessary decolourized by animal charcoal;
when the specific gravity has been again raised to 0·96, by the addition
of fresh alcohol, it may be used again.
The same process is applicable to textile fabrics, yarn, and leather.
Protection against Wood-worms, etc.
All the methods mentioned above will destroy insects and their larvae.
In cases in which it is either impossible or undesirable to use immersion
or external application, as for instance in the treatment of objects of
dry wood, the larvae may be destroyed by dropping petroleum, an aqueous
solution of potassium arsenite, or corrosive sublimate, into the various
small openings. This will also help to prevent further attacks.
If solutions are not applied insects may be destroyed by the vapour
of carbon bi-sulphide or of crude benzene. These liquids, which are
sufficiently volatile at the ordinary temperature, should be placed,
together with the objects to be treated, in a closed box.
I have used a similar method for the destruction of wood-worms in Egyptian
coffins. The coffin is placed in a large wooden box lined with tin plate.
The lid, also lined with tin, is provided with projecting edges, to which
strips of felt are glued. The weight of the lid by compressing the felt
is sufficient to render the box air-tight. Six or eight glass vessels
containing crude benzene are placed at the bottom of the chest and of the
coffin itself. It need scarcely be added that the box must not be opened
near a fire or light, as the vapour forms an explosive mixture with air;
it is in fact advisable to have no light or fire in the room.
Insects can also be killed by naphthalene vapour, but as naphthalene
is insufficiently volatile at ordinary temperatures, the method above
described is more convenient[173].
Preservation and Cleaning of Coloured Wooden Objects.
For objects of this kind materials should not be used which, like varnish,
tend to darken and so to damage the colours. Gum-dammar solution (page
70) answers the purpose, but colourless collodion is better. Colours which
are soluble in water (as is frequently the case with wooden objects from
Egypt) cannot of course be cleaned with water, but benzine may be applied
by means of soft cloths or brushes. Resinous or pitch-like substances may
often be removed from coloured objects by turpentine mixed with benzine
or ether.
A method of cleaning gilded or brightly coloured ecclesiastical figures
which is used in the Breslau Museum is the application of a mixture of
copaiba balsam and ammonia. This method is similar to that used to clean
paintings[174], the action of the solution being that of a mild soap.
Antiquities which were originally uncoloured, but which have been
subsequently painted, may be cleared of paint by means of a solution of
caustic soda in water or alcohol.
(_t_) Amber.
After the mechanical removal of any adherent earth and dust, the specimen
should be rubbed carefully backwards and forwards between the fingers
covered with a soft woollen glove. Particles of soil should be picked out
of any holes and indentations by using a strong horse hair[175]. It is
then preserved by impregnation with a solution of shellac, poppy-seed oil,
or isinglass (pp. 70 and 86).
The following particulars of the method used in Messrs Stantien and
Becker's collection of amber have been supplied by Prof. Klebs:
"Amber is preserved best in distilled water: I add a very small
quantity of glycerine and a still smaller amount of alcohol. A
proportion of alcohol greater than 1% is injurious to the amber.
A thick layer of gelatine containing glycerine is an excellent
medium for the preservation of large objects if they are kept free
from dust. This layer should be washed off and renewed every few
years."
The Care of Antiquities after Preservative Treatment.
In addition to the protection from dust afforded by closed glass cases, it
is also important to protect objects from the action of direct sunlight,
especially during the summer months. There is, for instance, no doubt
that the decay of bronzes, even of those with a patina which is apparently
sound, is hastened by the great variations of temperature, caused by the
rays of the sun falling directly upon them. Similarly objects which have
been preserved by the application of solutions of resin or varnish should
be protected from the direct access of sunlight, for the sudden warming
may easily cause cracks. Nor should antiquities be kept near the heating
apparatus. There is another precaution, to which too little attention
has been paid, viz. the protection of objects as far as possible from
even diffused daylight. Although no investigations upon the extent of
the injurious action of light have as yet been published, light is not
without influence upon the outward appearance, and therefore also upon the
material condition of antiquities of organic origin. But even inorganic
objects, such as pigments, glass, enamel, amber, etc., are affected by
light; it is therefore certainly advisable to protect antiquities of all
kinds from light during the time in which they are not exhibited to the
public.
The public is effectually prevented from fingering antiquities which are
enclosed in glass cases, but it may be well to remind those who have to
handle them in the course of their duties that contact with the bare hand
can only be harmful, even though fingering is understood to be beneficial
to modern bronzes by inducing the formation of patina. The bright surface
of metallic iron which results from treatment by Blell's or by Krefting's
method, especially if there is a thin coating of paraffin, should not
be touched at all with the bare hand, but only with a cloth or a glove.
Bronzes, whether intact or restored, and iron objects, should never be in
direct contact with those which show efflorescences.
The usual custom is to attach labels of painted cardboard or metal by
means of thin metal wire. The tendency to rust makes iron wire unsuitable,
especially for objects containing salt, which are quickly affected; thus
light coloured earthenware may soon be covered with spots of rust. Copper
wire and nickel wire are liable to be similarly attacked. Many years
ago it was noticed[176] in the Ethnological Museum at Berlin that nickel
wire when in contact with silver objects which were covered with silver
chloride was destroyed by the formation of a deliquescent green nickel
salt. Silver or platinum wire forms the most suitable means of attachment,
but if the expense of these is too great, copper or nickel wire may be
used, except in the cases mentioned above.
Small objects of any kind, which one still frequently finds kept in
open cases, are better preserved in upright glass cylinders with glass
stoppers, or in cheaper glass tubes, one end of which is fused and the
other closed with a cork.
Conclusion.
The methods of preservation which have been described in the preceding
pages may be thus tabulated and summarised:
Methods. Application.
Steeping in water, drying Limestone,
and impregnation. Earthenware,
Iron, much corroded.
Direct impregnation. (1) Unbaked earthenware, etc.,
(2) Bronze objects with little or
no metallic core, or showing a
cracked or warty surface,
(3) Objects of wood and of other
organic substances.
Removal of compounds of oxygen
or chlorine
(_a_) by chemical process, Iron objects in a good metallic
condition,
(_b_) by electrolytic process. (1) Iron objects with a sound
metallic core,
(2) Bronze objects with a sound
metallic core.
Mounted thoroughly dry and Valuable bronzes in an advanced
hermetically sealed. state of decomposition.
There will be no difficulty in the choice of methods for limestone or
earthenware, whether kiln-dried or sun-dried, for a simple experiment will
prove whether steeping is likely to cause injury or disintegration.
The methods are themselves simple and inexpensive. For organic substances
the chief question is the choice of the most suitable medium for
impregnation.
Iron and bronze present some difficulty, although the use of a file will
readily show whether reduction is feasible.
The simplicity of the apparatus required for Krefting's method gives it an
advantage over other methods, at any rate for iron objects. Objection has
been taken to the methods of reduction, because they give to the objects
thus treated an appearance to which the public are not accustomed. It may
be safely asserted however that this appearance more truly represents the
object when in actual use, than the oxidized and rust-covered specimens
to which we are accustomed in antiquarian collections. To those who value
an antique object for the crust that covers it, all methods of restoration
must be objectionable. Such persons ought to object to the removal of the
incrustations which hide the cuneiform inscriptions on clay tablets. On
the other hand, those who regard these methods with approval should go a
step further and confide their collections to experienced hands for some
form of treatment which may bring to light inscriptions and inlaid work
which will greatly enhance their value.
To spread the knowledge of these methods and to invite the co-operation of
others is the aim of this book. As to the best method to be used in each
particular case it is unnecessary to lay down any hard and fast rule, for
this can only be learned by observation and experience.
APPENDIX A.
METHOD OF TAKING SQUEEZES OF INSCRIPTIONS, ETC.
For this purpose a proper brush is required with strong bristles,
closely set as in a scrubbing brush; the brush should have a firmly fixed
handle, preferably slightly curving upwards to save the knuckles from
being bruised upon the stone. A so-called "silver brush" will serve the
purpose. The paper should be stout and stiff enough to resist the blows
of the brush without tearing. An admirable paper, which possesses these
qualities, is specially prepared for the purpose by the O.W. Company,
100, Great Russell Street, London, W. As a substitute for the specially
prepared paper stout packing paper may be used with satisfactory results.
The stone should be tilted if possible at an angle of about 45°, and the
surface bearing the inscription should be well washed or carefully scraped
free of dirt and foreign matter and should be rendered thoroughly wet. A
piece of the special paper of suitable size should be soaked in water for
a minute or more. It should then be carefully applied to the surface of
the stone in such a way as to prevent air-bubbles. This may be assisted
by gently smoothing it with the hand or back of the brush. When close
adhesion has been secured, and all air-bubbles removed (this can sometimes
be done by pricking through the paper with a pin), the paper should be
sharply beaten with the brush, the blows being delivered from the wrist
and not from the shoulder until it begins to show a fluffy appearance. It
should then be peeled off and allowed to dry, after which it may be rolled
or folded without danger of injury to the embossed inscription.
Should the paper tear, another piece soaked as before may be placed on
the top and beaten until it becomes incorporated with the first. If the
letters are large and deep, or if the surface is much cracked, two or more
sheets superimposed should be used. In the case of large inscriptions it
is advisable to take impressions by sections, care being taken that each
sheet slightly overlaps the preceding one to prevent the possible omission
of some of the letters.
It is also useful to take at the same time a pen or pencil copy of the
inscription, for a comparison of the copy and the squeeze will often
prevent errors in deciphering. The squeezes can be very well deciphered
by artificial light, while doubtful letters may sometimes become clear on
holding up the sheet to the light. The reverse side of the squeeze, upon
which the inscription stands in relief, may afford great assistance when
read by the aid of a mirror. A photograph of the squeeze will often reveal
more than a photograph of the inscription itself.
The method is described by S. Reinach in his "Traité d'Épigraphie Grecque"
(Introduction, p. XX.), where he also refers to Hübner, "Ueber mechanische
Copien von Inschriften," 1871.
APPENDIX B.
ZAPON.
Further particulars may be given of the new preparation known as Zapon.
This substance is now made on a large scale, and can be obtained from the
British Xylonite Co., Brantham Works, Manningtree (Xylonite lacquer F.
6631). The following excerpt is from a short communication in "Prometheus"
(XV. 1904, pp. 485 and 499), which deals with the preservation of wax
seals and of glass.
Zapon, the invention of Crane, of Shorthills, U.S.A., has been used
for 20 years past for the protection of metals from oxidation and the
action of sulphuretted hydrogen. Although the products of the various
manufacturing firms differ in composition, zapon is essentially a solution
of nitro-cellulose in various solvents. The nitrated cellulose, i.e.
gun-cotton (pyroxyline), is generally, with the addition of camphor,
dissolved in a mixture of amyl acetate (hence the peardrop-like smell)
to which distillation products of petroleum, etc., are added. It comes
into the market as a faintly yellow, slightly oily liquid. Its use as a
preservative depends upon the fact that the evaporation of the solvent
leaves behind it a fine transparent coating of gun-cotton (pyroxyline).
Zapon for preservative purposes must have a neutral reaction, and must not
under any circumstances redden litmus paper. Its use in this connection is
due to Schill, who also recognised its suitability for other materials,
as, for example, for plaster casts, the treatment of which is eminently
simple, for it consists in dipping small casts, or in painting larger
ones with a soft brush. It is advisable to begin at the top and apply
it from above downwards, using a clean dry cloth to wipe off any excess
of the fluid which collects in the deeper parts of the cast. If zapon
containing about 4% of gun-cotton is used, the coating left on drying
is scarcely visible; with a 5% solution a certain degree of polish
results. Casts treated with zapon are less easily damaged by dust than
those untreated, and may be cleaned with soap and water without injury
to their surface, provided that a soft brush is used, but brushes which
are stiff enough to injure the zapon coating will damage the contours of
the statue. It should only be used for objects kept under cover, for rain
and wide variations of temperature will attack them almost as readily
as untreated casts. It can be used with equal success for antiquities
of stone, clay, baked or unbaked, or for plaster after the soluble salts
have been thoroughly removed by steeping, for if this has not been done
the salts will soon crystallize out and loosen the protective coating.
For objects which are free from salts impregnation with zapon possesses
the advantage that it renders them less liable to damage from handling
or dust, whilst the appearance is scarcely altered, if at all. This
applies also to antiquities of metal, for unless the injurious chlorine
compounds are removed by simple steeping, or reduction and subsequent
steeping, treatment with zapon is useless. To bronzes, which in spite
of mechanical cleaning show a somewhat unpleasant grey non-metallic
appearance, zapon often imparts a distinct metallic lustre. To enhance
this lustre by a second vigorous application is not recommended, for this
gives the impression of a varnish. To protect articles of silver from the
blackening influence of sulphuretted hydrogen, zapon is very useful, but
does not afford absolute protection unless it has been thickly applied. In
collections of armour much use may be found for this material. The objects
are dipped and then placed in a drying oven at 105°F. [40°C.] to secure
rapid drying and uniform distribution. The amyl acetate or other solvent
is best conducted away, as it evaporates, into a flue or into the open,
although the vapours can hardly be considered dangerous to health.
The following references will afford some information on the use of zapon
in the preservation of Archives:
E. Schill, "Anleitung zur Erhaltung und Ausbesserung von Handschriften
durch Zapon-Imprägnierung," Dresden, 1899.
O. Posse, "Handschriften Konservirung," Dresden, 1899.
G. Sello, Das Zapon in der Archivpraxis ("Korrespondenzblatt des
Gesamtvereins der deutschen Geschichts- und Alterthumsvereine," L., 1902,
p. 195).
Schoengen, Over hat Zapon ("Nederl. Archivenblad," 1902, 1903, Nos. 1 and
3).
J. Perl, Das Archiv-Zapon ("Korrespondenzblatt," LII., 1904, pp. 119 and
435).
G. Sello, Die bei der Zaponverwendung in der Archivpraxis gemachten
Erfahrungen ("Korrespondenzblatt," LII., 1904, p. 439).
INDEX.
Acetic acid 150
Air-pump 68, 95, 129
Akermann 9
Alabaster 74
Alcohol 87, 93, 95, 132, 155, 161, 162
Jenner's method 159
preservation of leather 153
removal of oil by 87
Algae 10, 60, 76, 85
Alum 154, 158
Amber 55, 162
Ammonia
action upon bronze 18, 25, 31, 121
action upon silver 148, 150
Analyses
bronzes 22-27, 47, 138
iron rust 12
patina 23, 39
salt crystals 155
silver 51
silver chloride 51
Appelgren on application of Krefting's method 108, 115
Arche 27
Archives, preservation of, by zapon 170
Armour, iron, treatment of 105, 169
Assyrian tablets, treatment of 78, 81
Atacamite 21, 22, 26, 29
Azurite 17, 21, 36, 139
Bacteria, influence of, on iron 10
influence of, on bronze 28, 46
Barium chloride 77
Barium nitrate test 61, 77, 86
Barth 155
Bassett, analysis of bronze 25
Bees'-wax 90, 97, 102, 106, 153, 158
Bell-glass, use of 68, 95, 129, 152
Belmontyl oil 86
Benzene 91, 158, 160
Benzine 70, 86, 90, 95, 96, 106, 131, 161
Berthelot 28, 52
Bibra
on patina 20
on silver 52
Bille Gram 154
Bischoff 41
Blell 13, 91
Blell's method (iron) 102
Bolle 161
Bones, influence of contact with 14
preservation of 55, 152
Book-bindings, treatment of 152
Brewster's method (coins) 146
Bronze 15, 120
action of ammonia upon 18, 25, 31, 131
analyses of 23-27
analyses after reduction 138
Fellenberg's classification of 15
cleaning of 120
drying of 123, 131
impregnation of 122
incrustations, removal of 121
glue, treatment by 121, 125
hammers 120
heating 121
hydrochloric acid 121
inlaid metals upon 122
Springer's method 121
lead in bronze 24, 130
preservation of, by exclusion of air 144
preservation of, by carbolic acid 120
reduction of 125
Finkener's method 125
Krefting's method 139
Krefting's method (coins) 140
Villenoisy's classification of 32
Brushes, wire 107, 115, 131, 141
"silver brushes" 151, 166
Bucholz, experiment 18
Bunsen 54
Calcium chloride 123, 146
Carbolic acid 120, 157
Carbonic acid, influence of, on iron 8, 9
influence of, on bronze 31
Carbon bisulphide 90, 160
Caries of bronzes 26
Casts (plaster), zapon for 169
Caustic soda 110, 115, 119, 139, 140, 161
Celluloid 150
Cement for pottery 87
for stone 88
Ceresole, treatment of lead 150
Chevreul 21
Chlamydothrix 10
Chlorine, destructive action of 12, 26, 41, 46, 100, 121
estimation of 76
Church, analysis of silver 50
Citric acid 148
Clay, baked 4,81
Clay tablets, treatment of 78
Clay vases, sodium sulphate in 6
treatment of 80
Coffey, analysis of Irish celts 26
Coins, treatment of 139
Brewster's method 146
Krefting's method 140
Roux' method 147
treatment of, by melted lead 143
Collodion 71, 91, 161
Copaiba balsam 161
Copal varnish 90
Copper 15, 49, 120
absence of "edel-patina" 49
carbonate 21, 33
chloride 17, 21, 52
oxychloride 17, 21, 29, 41
preservation of 122
stannate 31, 33
sulphide 21, 24, 33
"Copper crystals" of bronzes 18
Corrosive sublimate 152, 154, 160
Covelline 23
Crenothrix 10, 60
Crum Brown 7
Cuboni 27, 46, 48
Cuneiform tablets 6, 78
Cupric oxide 18, 22, 33, 37
Cuprite 18
Cuprous oxide 17, 21, 24, 28, 37, 41, 52
Cyanogen 129
Damp, influence of 29, 43, 47, 49
Daniell cells 126
Davy 17
Dechend's apparatus 73
Dextrin 88
Dowris find, analysis of bronze from 26
Drude 147
Dunstan, on rusting 9
Dust extractor 131, 141
Dust, protection from 162
Earthenware
baked, impregnation of 78
baked, steeping of 74
unbaked, impregnation of 81
unbaked, treatment of 81
with colouring 79
"Edelrost" 14
Edel-patina 49, 120
Egypt, soil of 1
dry climate of 2, 56
Egyptian bronzes 130, 134, 138
absence of "edel-patina" in 42
high chlorine-content in 42
lead in 24, 33, 130
Egyptian coffins 160
Egyptian coloured objects 161
Egyptian textile fabrics 154
Egyptian ostraca 4, 57
efflorescences upon 4
treatment of 75
Ekhoff's method (iron) 96
Electric current a cause of rust 9
Electric muffle furnace 84
Electrolysis 111, 126, 147, 148
Elster 23
Enamel 151
Ephesus, bronze from 25
Ether 74, 90, 133, 161
Fat 106, 107
Fayence 6, 86
Feathers 154
Fellenberg 15
Finkener's method (bronze) 125
Fire-clay 84, 88
Fire-clay dust cement 88
Fish-glue 86, 88
Flinders Petrie 1, 71, 87, 119
on impregnation of earthenware 81
on reduction of silver 148
Fluates 71
Forge scale 8, 14, 104
Formalin 60, 152
Friedel 46
Gallionella 10
Gelatine 162
Glass, changes in 54, 151
Glue 87, 88, 120, 151
Glycerine 157, 159, 162
Gold, changes in 53
treatment of 150
existence of, in silver objects 50
ferric oxide upon 53, 151
Granite 87
Gum arabic 88
Gum dammar 70, 95, 101, 149, 151,
161
Gypsum 74, 81
Haidinger, on patina 21
Hair 55, 153
Hammers 120
Hartwich's method (iron) 117
Hassack, on patina 27
Heat-recorders 84
Herbst's method (wood) 158
Hierli, on textile fabrics 153
Hildesheim silver-find 49, 51
Horn, changes in 55
treatment of 151
Horn-silver 49, 51
Hünefeld 17
Hydrated ferric oxide 60
Hydrated tin oxide 130, 138, 139
Hydrocyanic acid 126
Hydrochloric acid 78, 84, 85, 87,
111, 116, 121, 126, 129, 149, 150
Hydrogen, reduction of bronzes in
(Finkener's method) 22, 125
Hydrogen, reduction of iron in
(Hartwich's method) 117
Impregnation media
bronze and iron 90
limestone 70
Incrustations, bronzes 37, 120, 128
earthenware 78
limestone 74
silver 149
India-rubber solution 90, 153
Ink upon ostraca 75
Inlaid metals 100, 136
Inscriptions, "squeezes" of 166
Insects, attacks of 154, 160, 161
Iridescence of glass 54
Iron 7, 89
absence of antiquities of iron in Egypt 14
acid bath for 103
alcohol, steeping in 93, 95
bone-ash, influence of 14
chain-mail 105
ferric chloride 12, 93
ferric hydroxide 7, 93
ferric oxide 14
ferric oxide on gold 53, 151
ferroso-ferric oxide 8, 14, 101
ferrous chloride 13, 92
ferrous oxide 14
ferrous phosphate 14
ferrous sulphide 60
heating of iron 92, 99, 106
impregnation of iron 93
impregnation media for iron 90
inlaid work upon iron 100
linseed-oil for iron 91
medieval iron objects 85
methods of treatment:
Blell's method 102
Ekhoff's method 96
Hartwich's method 99, 117
Jacobi's method 99
Krause's method 92
Krefting's method 108
Steffensen's method 102
Straberger's method 97
"Passivity" of iron 119
Reduction by heat 99
Reduction by potassium cyanide 118
Reduction by potassium sulphocyanide 119
Rusting, see "rust"
Irvine 8
Isinglass 90, 98, 100, 151, 156, 162
Ivory 55, 151
Jackson 10
Jacobi 14
Jacobi's method (iron) 99
Jenner's method (wood) 159
Karabacek 1
Kessler's fluate 71, 72, 74
Kisa 143
Klebs, on amber 162
Krause's method (inlaid iron) 101
Krefting, analysis of rust 12
experiments of 10, 45
method for bronze 139, 140
method for iron 101, 108, 118
method for lead 150
theory of rust 8
Kröhnke 9, 48
Lanoline 152
Lead, changes in 31, 53
treatment of 149
treatment of coins with 143
Lead carbonate 53, 150
Lead oxide 33, 90
Lead stannate 31
Leaden objects, Ceresole on 150
Leather 152
preservation of, at Salzburg 56
Lechat 30
Lecythoi, treatment of 80
Leiner's method (wood) 157
Lemery 10
Lepsius 67
Light, influence of 10, 60, 162
Lime, incrustations of 74
Limestone 57
action of salts upon 2
changes in 2
drying of 67
dust, removal of 58
impregnation of 51, 68
impregnation media for 70
steeping 58, 66
disadvantages of 67
test of progress of 62
Linseed oil 71, 90, 91, 97, 99
Linseed varnish 90, 91, 93, 99
Magnesium sulphate 5
Malachite 17, 18, 21, 36, 139
Marble 72, 74
Medieval iron objects 119
Mêdûm, analysis of bronze from 26
"Métaux malades" 29
Meten chamber
description of 2
limestone blocks from 56, 67
impregnation of 73
steeping of 59, 64
table of results of steeping 65
Milbauer 119
Mitzopulos, on patina 24
on silver 51
Mond, on patina 27, 46, 48
Moody, on rusting of iron 9
Moulds, attacks of 72, 157
Muffle furnace 84
Mycene, copper alloys from 24
silver from 51
Naphthalene 154, 161
Natterer, analysis of Ephesian statuette 25
Neufeld 10
Nickel wire for labels 163
Nile mud, objects of 87
Nitric acid, action upon iron 119
Oak, objects of 159
Oil colours, removal of 87
Oleate of lead 90
Olive oil 90, 151
Olshausen _vii_, 11, 48, 55
Organic substances
changes in 54
influence of, on patina 31
treatment of 151
Ostraca, _see_ Egypt
Oxygen, influence of 54
Paint, removal of 87, 161
Papyrus 154
crystals from 155
treatment of 155
zapon useful for 156
Paraffin wax 71, 85, 91, 95, 97, 115, 118, 125, 132, 141, 149, 157
Patina
composition of 16
heat, action of upon 28, 122
varieties of
black 33
blue 32
cracking 122
creeping or malignant 28, 125
"edel-patina" 34, 120
green 16
warty 38
Peat, influence of
bronzes 15, 33
iron 13
organic substances 55
hair 154
Pepper (for feathers) 154
Petroleum 93, 96, 97, 157
Petroleum ether 71
Phosphoric acid 14
Picht 17
Pile-dwellings
antiquities from 53, 156
horn and wool 55
textile fabrics 153
Plaster of Paris 88, 156
Pole paper 127
Poppy-seed oil mixture 70, 86, 151, 162
Potassium
arsenite 160
carbonate 148, 149
chromate 62, 130
cyanide 118, 126, 148, 149
iodide 126
sulphate 1
sulphocyanide 119
Priwoznik, on patina 23
Quicklime 96, 115
Reduction
bronze 125
iron 99, 118, 119
Rein, on Japanese bronze 36
Reinach, on inscriptions 167
Resin 91, 158, 162
Resin, removal of 74, 161
Reuss, on patina 17
Rhousopulos
treatment of bronze 111
treatment of earthenware 80
treatment of iron 111
treatment of marble and limestone 72
Rice water 71, 72
Rogna, variety of patina 26
Roux, method of cleaning coins 147
Rubber solution 90, 153
Rust
bacteria, a cause of 10
"edel-rost" 14, 111, 118
removal by acid 103
removal by sodium sulphide 119
theories of causation 7
Salt crystals, analysis of 155
Salzer 93, 95
Sandstone, treatment of 87
Schertel 51
Schill 168
Schliemann 26
Schuler, analysis of patina 24, 48
Schulz, analysis of bronze 138
Seger cones 82
Setlik 110
Shellac 70, 86, 88, 90, 147, 162
Silver, analysis of 50, 51
changes in 49, 149
electrolytic treatment of 148
preservation of 148
"Silver brushes" 151, 166
Silver chloride 49, 51, 52, 148
Silver nitrate solution 61, 76, 78, 93, 130
Silver subchloride 49, 51
Silver sulphide 50, 149, 168
Simon 8
Size 71, 72, 86, 90, 156
Soda 87, 93, 97, 98, 102, 106, 115
Sodium chloride 1, 4, 5, 10, 47, 56, 61, 85, 93, 148
Sodium nitrate 6
Sodium sulphide 119
Speerschneider's method 91, 158
Spennrath 8
Spray apparatus 73
Springer's method 120
Squeezes of inscriptions 166
Stapff 8
Stavenhagen 46
Stearine 71, 92
Stearine glaze 152
Steel wire brushes 107
Steeping
baked clay 85
bronze 130
earthenware 74
iron 92
limestone 59
Steffensen's method (iron) 102
textile fabrics 153
wood 159
Stolba 21
Stone cement 88
Straberger 162
Straberger's method (iron) 97
Stucco 87
Sulphates, test for 61, 77, 86
Sulphur, influence of 31
Sulphuretted hydrogen 24, 31, 61, 169
Sulphuric acid 13, 102, 107, 116, 123
Sunlight, _see_ Light
Süpke 146
Syndeticon 87
Tannic acid, influence of 13
Tapioca water 71, 72
Terra-cotta 74
Terreil 23
Test for progress of steeping 61
Textile fabrics 153
Tin, changes in 31, 53
treatment of 149
Tin oxide 22, 37, 41, 53
Tin, proportion of, in patina 26, 48
Titration 5, 61
test in connection with 61
Tolomei 8
Train oil 152
Turpentine 70, 90, 153, 161
Unbaked clay 81
Varnish-benzine mixture 71, 74, 75, 78, 81, 85, 87
Vaseline 90
Verdigris 16
Villenoisy, on patina 30
classification of 32
Vivianite 14
Volney 1
Voss _v_, 163
Wagner 10
"Wall-saltpetre" 7
Warrington 51
Water-bath 94
Waterglass 71, 72, 88, 90, 157
Watkin's heat-recorder 84
White of egg solution 86, 153
Wibel 16, 17
Wire for labels 163
Wood, treatment of
Herbst's method 158
Jenner's method 159
Leiner's method 157
Speerschneider's method 158
coloured wood 161
large objects, varnish for 157
Wood-worms 160
Wool, changes in 55
preservation of 153
Yarn 160
Yorkshire, analysis of bronze from 26
iron objects from 113, 114
Zapon 71, 81, 118, 132, 149, 150, 156, 168
Zinc 31, 110, 116, 138, 139, 140, 150
Zinc oxide 31, 111, 141
Zylonite lacquer, _see_ Zapon
CAMBRIDGE: PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS.
FOOTNOTES:
[1] "Lexikon d. gesamten Technik," Vol. I. p. 257. O. Lueger.
[2] "Merkbuch." The excavation and preservation of Antiquities, 2nd
edition, Berlin, 1894.
[3] "Mittheilungen aus der Sammlung der Papyrus Erzherzog Rainer." Vol.
I. p. 118. See also Flinders Petrie, Archaeological Journal, Vol. XLV.
1888, p. 88.
[4] Aeg. 105. [This and similar notes have reference to the catalogue of
the Egyptian (Aeg.) or Antiquarian (Ant.) sections of the Berlin Royal
Museums.] The limestone blocks were brought from the Mastaba of Meten,
at Abusir near Memphis, explored by Lepsius in 1846. Meten was one of
the chief officials under King Snefru, B.C. 2800. The inscriptions
relate to his possessions and official career, while the pictorial
representations depict hunting scenes and the offering of the gifts for
the dead. The statue of Meten was found in the grave and is now in the
Egyptian department (No. 1106) of the Royal Museum. Comp. "Ausführliches
Verzeichniss der aegyptischen Alterthümer," Berlin, 1899.
[5] Aeg. P. 4730
[6] Aeg. V. A. 2846.
[7] Aeg. P. 4739.
[8] It may be here mentioned that, as is well known to chemists, the
efflorescences which often go by the name of "wall-saltpetre," in most
cases do not contain any saltpetre, but consist of sodium sulphate.
[9] Crum Brown, "Chem. Centralblatt," 1890, I. p. 212; E. Simon, "Ueber
Rostbildung u. Eisenanstriche," p. 4.
[10] J. Spennrath, "Verhandlungen d. Vereins zur Beförd. d.
Gewerbefleisses," 1895, p. 245.
[11] "Christiania Videnskabs-Selskabs Forhandlinger" for 1892, No. 16, p.
8.
[12] "Chemische Zeitung. Repetitorium," 1895, p. 289.
[13] "Chem. Centralblatt," 1895, I. p. 441.
[14] Id., 1891, I. p. 860.
[15] "Berg- und Hüttenmännische Zeitung," 1882, p. 469.
[16] [It may not be out of place here to give the main conclusions, drawn
from a long series of experiments by Prof. W. R. Dunstan ("Proc. Chem.
Soc.," XIX. 150, 1903).
(_a_) Pure iron is not oxidised in the presence of gases and water-vapour
only, but for the appearance of rust the presence of water in the liquid
state is necessary.
(_b_) The reagents which prevent the rusting of iron are those in
the presence of which hydrogen peroxide is decomposed, and which are
consequently inimical to its formation: among such reagents the following
are given--sodium chloride, sodium sulphate, ferrous sulphate and
potassium nitrate.
(_c_) The action of H_{2}O_{2} on metallic iron leads to the production
of red basic ferric hydroxide, which is identical with ordinary rust.
The composition of rust may therefore be represented by the formula
Fe_{2}O_{2}(OH)_{2}, the reaction being represented by the equations:
Fe + O_{2} + H_{2}O = FeO + H_{2}O_{2}.
2FeO + H_{2}O_{2} = Fe_{2}O_{2}(OH)_{2}.
These views are however combated by Moody ("Proc. Chem. Soc.," XIX. 157
and 239) who concludes that aerial rusting must be regarded as a change
involving the interaction of iron and carbonic acid and the subsequent
formation of rust by oxidation of the ferrous salt.
He also states that those salts which do not combine with and which are
not decomposed by CO_{2} have no retarding influence on the formation of
rust, e.g. sodium chloride, sodium sulphate, etc.
On the other hand substances which absorb and combine with carbonic
oxide (e.g. sodium carbonate or hydroxide, ammonium carbonate, calcium
hydroxide), or which are decomposed by carbonic acid (potassium and sodium
nitrites), inhibit rusting, which may therefore be regarded as a change
involving the interaction of iron and acid and the subsequent formation
of rust by the oxidation of the ferrous salt.
O. Kröhnke ("Wochensch. Brauerei," XVII. 233) gives the following
equations:
Fe + 2CO_{2} + H_{2}O = Fe(HCO_{3})_{2} + H_{2}.
2Fe(HCO_{3})_{2} + O + H_{2}O = 2Fe(OH)_{2} + 4CO_{2}.
Comp. also Dammer, "Handbuch der anorg. Chem.," Vols. III. and IV.
(supplement).
Considerable attention has also been directed to the influence of bacteria
upon iron. Thus the growth of Crenothrix may cause much trouble in
waterworks, vide "Centralblatt für Bakterien und Parasitenkunde," II. 12,
681. A variety, Chlamydothrix (Gallionella) ferruginea (Mig.) appears to
play an important part in the formation of rust (comp. Zopf, "Crenothrix
polyspora die Ursache der Berliner Wasser-Calamität," Berlin, 1879. De
Vries, "Unter. der Crenothrix Commission," Rotterdam, 1887 and 1890).
Neufeld ("Chem. Centralblatt," 1904, I. 1621--abstracted from "Zeitschrift
für Untersuchung der Nährungs- und Genussmittel," VII. 478) gives
particulars of three varieties: Crenothrix polyspora, which separates
iron; Cr. ochracea, which separates aluminium and some iron; and Cr.
manganifera, which separates manganese.
Jackson ("Journal of Society of Chemical Industry," 1902, p. 681) gives
micro-photographs of these varieties. Microscopically the masses of
Crenothrix are seen enclosed in a gelatinous sheath, in which is imbedded
the precipitated metallic hydrate. It is anaërobic and its action is
favoured by absence of light. In the absence of dissolved oxygen, the
bacillus appears to take its iron from the pipes. Cr. polyspora is found
however ("Zeitschrift für analytische Chemie," XLII. 590) to separate the
iron not from the ferrous carbonate (FeCO_{3}) but from iron organically
combined. See also Winogradsky, Ueber Eisenbakterien, "Bot. Zeit.," 1888,
and "Chem. Centralbl." 1904, II. 1332. Transl.]
[17] Wagner in Dingler's "Polyt. Journal," CCXVIII. p. 70. Axel Krefting
in the above-quoted "Forhandlinger," p. 4.
[18] Olshausen often noticed on freshly excavated antiquities of various
kinds a peculiar smell of resin or gum, especially after treatment with
hydrochloric acid ("Verhandl. d. Berl. anthropol. Ges.," 1884, p. 520).
It may be supposed that this odour is due to the traces of hydrocarbons
present.
[19] Termed by E. Friedel "Dunstperlen." "Eintheilungsplan d. Märk.
Prov.-Museums," p. 9.
[20] "Om Konserviring af Jordfundne Jernsager," in "Aarsberetning fra
Foreningen till norske Fortidsmindesmaerkers Bevaring," 1892, p. 52.
[21] Krause, "Verhandl. d. Berl. anthropol. Ges.," 1882, p. 533.
[22] Private communication.
[23] "Sitzungsberichte der Alterthumsgesellschaft Prussia," 1881-2, p. 9.
[24] Merkbuch, Alterthümer aufzugraben und aufzubewahren, 2nd edition, p.
71.
[25] [This fact was noticed by Sir Thomas Browne, 1658, cp.
"Hydriotaphia," cap. iii. Transl.]
[26] In this work the Patina on antiquities only is considered; with that
on modern bronzes we are not concerned.
[27] "Mittheilungen d. naturforsch. Gesell. in Bern," 1865, p. 12.
[28] "Mitth. d. naturforsch. Gesellschaft in Bern," 1860, p. 69.
[29] "Jahrbuch für Mineralogie," 1860, p. 813.
[30] Malachite, CuCO_{3}, Cu(OH)_{2}.
[31] Azurite, 2CuCO_{3}, Cu(OH)_{2}.
[32] "Jahrbuch für Mineralogie," 1865, p. 400.
[33] The extract which here follows is in part verbatim.
[34] "Annalen der Chemie u. Pharmacie," 1853, Vol. LXXXV. p. 253.
[35] Von Bibra, "Die Bronzen und Kupferlegirungen," p. 206 _et seq._
[36] See the very full quotation from Wibel's work given above.
[37] I have not been able to find anything on this point in the literature
of the subject.
[38] Atacamite, CuCl_{2}, 3Cu(OH)_{2}.
[39] Cf. "Comptes rendus," 1856, XLIII. p. 735.
[40] "Journal f. praktische Chemie," XCIV. 1865, p. 314.
[41] "Verhandl. d. Ver. z. Beförd. d. Gewerbf.," 1869, p. 182.
[42] Dingler, "Polyt. Journal," 1878, Vol. CCIV. p. 483.
[43] "Berg- u. Hüttenmännische Zeitung," Vol. XXXVII. 1878, p. 329.
[44] Dingler, "Polyt. Journal," 1879, Vol. CCXXXII. p. 333.
[45] [Several other analyses of bronzes from various sources have been
recently published. Thus Natterer ("Monatshefte für Chemie," XXI. 256,
1900; also "Chem. Centralblatt," 1900, I. 1262) examined a corroded bronze
statuette from Ephesus. The bronze contained:--Tin 6·09%, lead 4·87%, and
copper 89·64%, with traces of zinc.
Bassett ("Proc. Chem. Soc.," 1903, XIX. 95) gives an analysis of the base
of an Egyptian statuette, found in the Nile Delta, probably dating from
200-100 B.C. The base was hollow but filled with lead, and was covered
with a thick green coating, which in parts entirely replaced the original
metal.
Table I.
Cu 50·65%
Pb 6·74%
Sn 2·94%
Fe 0·15%
Ni, Mn, etc. 0·11%
Cl 15·71%
SiO_{2} (as sand) 1·14%
H_{2}O 11·07%
(NH_{4}) 0·11%
-------
88·62%
Table II.
CuCl_{2} 29·34%
CuO 46·10%
H_{2}O 11·07%
SnO_{2} 3·73%
PbO 7·26%
Fe_{2}O_{3} 0·22%
NiO, etc. 0·14%
SiO_{2} 1·14%
(NH_{4})Cl 0·32%
-------
99·32%
In the second column the chlorine has been calculated as copper chloride,
the remaining copper and other metals as oxides.
Traces of calcium were also found, but the amount of sodium was so small
that it could only be detected by the flame test. If all the copper
had been present as basic chloride (atacamite CuCl_{2}, 3CuO, 3H_{2}O),
this would require 26·84% CuCl_{2}, 47·57% CuO, and 10·78% H_{2}O. It
would therefore appear that the substance produced by corrosion is less
basic than atacamite, and that ammonium chloride may have played a more
important part than sodium chloride in the formation of copper chloride,
for in this case the sodium was only found in amount too small for
estimation.
An analysis of the earliest piece of bronze known, i.e. that from Mêdûm,
Egypt (3700 B.C.), gives 8·4% of tin (inner core 9·1%) to 89·8 of copper
with a small quantity of arsenic.
An analysis of a celt from the Dowris find (King's County, Ireland, 1825)
gave copper, 85·23; tin 13·11; lead 1·14, with traces of sulphur and
carbon. The waste material from the same place yielded 89% copper, 11%
tin, with traces only of lead, iron and silver.
On the other hand an early bronze celt (Butterwick, E.R., Yorks.) showed
a smaller quantity of tin--10·74%, compared with 87·97% of copper. (Guide
to Bronze Age Antiquities, British Museum.)
Mr George Coffey has also published ("Brit. Assoc. Reports," 1899, p. 873)
a tabulated series of analyses of Irish celts which proved to be composed
of practically pure copper. Transl.]
[46] Schliemann, "Ilios," pp. 527 and 571.
[47] "Verhandl. d. Berl. anthropol. Ges.," 1882, p. 537.
[48] Dingler, "Polyt. Journal," 1884, Vol. CCLIII. p. 514.
[49] It should be observed that the change in the proportions according
to Schuler (see page 24) is only true of the analysis, Column III. In
Columns I and II the amount of metallic copper of the patina is indeed
smaller, but so is also that of lead and especially of tin. But this may
be due to a faulty method in the determination of tin noticed by Olshausen
(v. "Verhandl. d. Berl. anthropol. Ges.," 1897, p. 349). The different
proportion of the copper compounds in the patina should also be noted,
Schuler giving carbonate and hydrate in the proportion 1:1, Arche and
Hassack once as 1:2, and again as the result of two analyses as 1:3.
[50] "Atti della Reale Accademia dei Lincei," 1893, p. 498.
[51] "Étude sur les métaux découverts dans les fouilles de Dahchour" in
"Fouilles à Dahchour." March-June, 1894, p. 131 _et seq._ J. de Morgan.
See also "Comptes rendus," 1894, I. 118, p. 768.
[52] "Revue archéologique," v. 28, 1896, pp. 67 and 202. In the
publication for the second half of the same year Lechat maintains the
assertion (comp. Elster, p. 23) that in many cases the antique patina is
due to the artist.
[53] Ant. Misc. 7382.
[54] J. J. Rein, "Japan," Vol. II. p. 528.
[55] Ant. Misc. 8579.
[56] According to Graham-Otto, "Lehrbuch der Chemie," Vol. III. p. 849,
cuprous oxide is decomposed by dilute acids which contain oxygen; the
cupric oxide is dissolved and metallic copper remains.
[57] Buto, Aeg. 11867.
[58] Ant. Fr. 29.
[59] [The extraordinary deformation produced by this type of patina may be
judged from the fact that the features in this instance were so obscured
that the nature of the specimen was not recognised and it had accordingly
been mounted upside down. Transl.]
[60] Ant. Fr. 53.
[61] Ant. Fr. 53.
[62] Bischoff, "Das Kupfer und seine Legirung," p. 43. Layard,
"Discoveries in the ruins of Nineveh and Babylon," p. 191. Fellenberg,
"Mittheilungen d. naturforsch. Ges. in Bern," 1860, p. 68.
[63] "Christiania Videnskabs-Selskabs Forhandlinger" for 1892, 16, p. 5.
[64] [Having been broken off and soldered, the base was not subjected to
treatment. Transl.]
[65] E. Friedel, "Eintheilungsplan des märk. Provinzialmuseums," 1882, p.
20.
[66] Aeg. 2348.
[67] Aeg. 13787.
[68] Olshausen, "Verhandl. d. Berl. anthropol. Ges.," 1884, p. 532, and
1897, pp. 346-7. Kröhnke, "Chem. Untersuchungen an vorgeschichtl. Bronzen
Schleswig-Holsteins," p. 41. See also quotation from Schuler, p. 25.
[69] [This celebrated hoard was found Oct. 9, 1868, on the Galgenberg,
near Hildesheim (Hanover), 10 feet below the surface. It consisted of
more than 60 pieces, including plates, dishes, tripods, etc., the most
notable being a crater, 15-1/2 inches in height, ornamented with graceful
scroll-work, and a cylix with an Athene in high relief. The workmanship
points to a date not later than the first century A.D. Cp. Wieseler, "Der
Hildesheimer Silberfund," Bonn, 1869. Darcel, "Trésor de Hildesheim,"
1870. Transl.]
[70] Compare also the analysis by Schertel, p. 51.
[71] "Polytechn. Centralblatt," 1871, p. 916.
[72] "Polytechn. Centralblatt," 1871, p. 917.
[73] "Berg- u. Hüttenmänn. Zeitung," 1878, No. 37, p. 327.
[74] Dingler, "Polyt. Journal," 1871, Vol. CCI. p. 52.
[75] v. E. v. Bibra, "Ueber alte Eisen- u. Silberfunde," p. 74.
[76] Morgan, "Fouilles à Dahchour," p. 135.
[77] "Verhandl. d. Berl. anthropol. Ges.," 1897, p. 348.
[78] Krause, "Verhandl. d. Berl. anthropol. Ges.," 1883, p. 360.
[79] Muspratt's "Chemistry," Vol. III. p. 1389.
[80] "Verhandl. d. Berl. anthropol. Ges.," 1889, pp. 243 and 244.
[81] Id. 1892, p. 449.
[82] Id. 1897, p. 347.
[83] At that time obtained from the Stralau waterworks.
[84] This was not the well-known Crenothrix only. Cp. "Polytechn.
Centralblatt," 1891-92, p. 195. (See footnote, p. 10.)
[85] It has been found that the formation of this layer of slime may be
avoided by the use of tubs which are lined with sheet zinc. The addition
of 10-20 cubic centimetres of formalin [40% solution of formaldehyde] to
every hundred gallons of water also prevents or restrains the formation of
slime. It is not necessary to add formalin each time the water is changed.
[86] Since chlorine compounds (especially common salt) form the
predominating substance in the soluble salts contained in limestones
their removal may be considered a proof that other salts (e.g. sulphates)
have also been removed. Hence it is sufficient to prove the disappearance
of chlorine. In the rare cases in which sulphates only are present,
a test similar to that mentioned on p. 77, applied to clay objects,
should be used. If the water used for soaking salt-containing limestone,
earthenware, etc., gives no precipitate, or only turbidity with the silver
solution, the determination of chlorine by titration is not applicable.
[87] Though some other kinds of burette may be easier to use, that here
recommended (that of Gay-Lussac) is the most convenient for reasons into
which we need not enter. The following precautions should be observed:
where the burette is not closed by a cork, let a few drops out first
to wash away crystals of silver nitrate which may have formed at the
mouth. The silver solution should be kept in well stoppered bottles. When
filling the burette a glass funnel should be used, so that the cork used
for closing the burette is not wetted with the silver solution. Before
reading off wait until the level of the fluid is constant, in order that
any solution on the sides of the glass tube may have time to run down.
[88] See note, p. 61.
[89] I have found that the amount of chlorine is smaller in winter than
in summer. In the summer of 1894, 100 c.c. tap-water from the Stralau
Waterworks often required 0·8 c.c. silver solution: but at that time
stronger disinfectants were used on account of the cholera, and this may
have caused the increase of chlorine; for since then, and even at the
present time (winter 1898), 100 c.c. tap-water requires 0·5 to 0·6 c.c.
silver solution.
[90] It may be here observed that objects of limestone or of earthenware
may be numbered or marked at the back in black iron ink, which does not
disappear even after prolonged steeping in water.
[91] Lepsius, "Denkmäler aus Aegypten und Aethiopien."
[92] It is scarcely necessary to add that any other form of air-pump may
be used.
[93] A powerful pressure of water [in combination with a well-acting pump]
may cause the fluid to evaporate with such rapidity as to produce bubbles,
but these bubbles are easily distinguished by their size from the minute
bubbles of air. To avoid this ebullition, the air should not be pumped
out too rapidly.
[94] "Merkbuch," p. 62.
[95] Flinders Petrie, "Archaeological Journal," Part 45, 1888, p. 88.
[96] Zapon: for further information and references see Appendix.
[97] "Chemische Zeitschrift," ii. 1903, p. 203.
[98] For particulars of the composition and action of Kessler's Fluates
(salts of Hydrofluosilicic acid) see H. Hauenstein, "Die kessler'schen
Fluate" (2nd ed., Berlin, 1895). The depot is "H. Hauenstein, Berlin N.
Reinickendorferstrasse, 2b."
[99] Ger. Patent, No. 31032. The apparatus was one of those used in the
moulding room of the Royal Museums for the impregnation of plaster moulds
and casts.
[100] In applying the above test it is advisable to add one or two drops
of nitric acid before the addition of the barium salt. In this case, too,
should any other than distilled water be used for steeping, a preliminary
examination should be made to determine the presence or absence of
sulphates.
[101] [Pure hydrochloric acid is usually sold in two strengths.
Concentrated acid has a strength of about 32%, whilst the "diluted
hydrochloric acid" of the Pharmacopoeia is about 10%. The former should
therefore be diluted with about 15, the latter with about 4 volumes of
water. Transl.]
[102] "Chemische Zeitschrift," II. 1903, p. 761.
[103] [Lecythoi: slender narrow-necked painted vessels which
were frequently burnt or buried with the dead; cp. Aristophanes,
"Ecclesiazusae," 996:
#hos tois nekroisi zôgraphei tas lêkythous.# Transl.]
[104] The method of washing objects of unbaked clay suggested by Flinders
Petrie in the "Archaeological Journal" (XLV. 1888) is in my experience
impracticable.
[105] [Muffle furnaces may be obtained from Messrs Fletcher, Russell and
Co., Warrington. If electricity is available, the electric muffle may be
used. These may be obtained from Messrs A. Gallenkamp and Co., 19, Sun
Street, Finsbury Square, London. The Heat-recorders supplied by H. Watkin,
225, Waterloo Road, Burslem, will be found very convenient in place
of Seger's cones, which may be obtained from Messrs Brady and Martin,
Northumberland Road, Newcastle-on-Tyne. Transl.]
[106] "Merkbuch," p. 78.
[107] [A paraffin prepared from Burmese petroleum. Transl.]
[108] Flinders Petrie, "Archaeological Journal," XLV. 1888, p. 89.
[109] "Merkbuch," p. 79.
[110] [It is important to avoid confusion and mistakes arising from the
similarity of the terms benzine and benzene.
Benzene (Benzol) is the specific coal-tar product which has the formula
C_{6}H_{6}.
Benzine (Benzin) is a light-boiling petroleum distillate, lighter than
lamp oil, and with a varying boiling-point. It consists of a number of
saturated hydrocarbons of the methane series. It is also called benzoline
or petroleum naphtha. Transl.]
[111] Appelgren, Finskt Museum, 1895, p. 56.
[112] A communication from Herr Schjerning, Copenhagen.
[113] Speerschneider, "Antiquarisk Tidsskrift," 1858-60, p. 178.
[114] Blell, "Sitzungsberichte der Prussia," 1881-82, p. 24.
[115] Krefting, "Aarsb. fra foreningen t. norske fortidsmindesm. bevar."
1892, p. 54.
[116] Salzer, "Chem. Zeitung," XI. 1887, p. 574.
[117] Probably first recommended by Salzer, "Chemiker Zeitung," XI. 1885,
p. 574.
[118] "Kongl. Vitterhets Historie och Antiqvitets Akademiens Månadsblad,"
1885, p. 134.
[119] The addition of the lime is not advisable, comp. p. 93.
[120] "Chemiker Zeitung," XI. 1885, p. 605.
[121] "Zeitschrift f. Ethnologie," XXXIII. 1902, p. 431, and XXXIV. 1903,
p. 791.
[122] "Sitzungsberichte," 1881-82, p. 10 _et seq._, and 16 _et seq._
[123] In this acid treatment bare hands may be used, but care must be
taken to avoid splashing clothes or linen, which will cause red or yellow
spots. These are best removed by the immediate application of ammonia,
but the yellow spots can only be removed by oxalic acid.
[124] [Germ. "Hammerschlag." The iron scales which chip off from heated
iron at a forge or blacksmith's shop. Transl.]
[125] No. 17, 1897, p. 333 _et seq._
[126] A number of modifications in the metals employed and the composition
of the bath have been suggested. Setlik ("Chemiker Zeitung," XXVII. 1903,
p. 454) imbeds iron objects which have a very weak core in a zinc-wire
basket immersed in a magma of zinc dust and caustic soda. Personally I
should prefer not to attempt a reduction process in such cases, but should
rely rather upon mechanical removal of the rust, soaking and impregnation.
For the treatment of bronzes this observer prefers the Finkener method
(q. v.) and suggests caustic soda, sodium chloride, or ammonia chloride,
instead of potassium cyanide as the electrolyte. Rhousopulos ("Chemische
Zeitschrift," II. 1903, pp. 202 and 364) uses zinc and hydrochloric acid,
and when dry gives to the bronze a coating of wax. I should deprecate
the use of either of these substances, the hydrochloric acid because of
the difficulty of completely removing it by steeping and the danger of
subsequent decomposition of the bronze, the wax because the contained
fatty acids may act upon the metal.
[127] [The period required for complete reduction is, in our experience,
often considerably longer. We have sometimes found an 8% soda solution
more satisfactory. Transl.]
[128] Krefting's method affords an excellent illustration of the
truth of my remarks in the preface that the literature upon these
preservation-methods is very scattered and in consequence has been
hitherto but little studied. In 1892, when visiting the Museum at
Christiania, I had the opportunity of examining some iron objects which
had been treated by Krefting's method. I then obtained his address, and
Herr Krefting kindly communicated his method to me by letter, and in the
following year forwarded a reprint of his article referred to above. In
1887 he had described his method to Appelgren by letter, but at that
time he treated the object after reduction, washing, and drying, by
impregnating it with a paraffin-petroleum solution. In 1897 Appelgren
published this method, with drying and impregnation, in ignorance of
Krefting's publication in 1893.
[129] The bottle should not be closed by a glass stopper, but by a rubber
bung, or by a cork coated with paraffin or wrapped round with parchment.
Soda solution attacks glass, and especially ground glass; thus the stopper
may become so firmly fixed into the neck of the bottle as to render its
removal impossible.
[130] [Excavated by Dr Thurnam, 1848 (vide "Archaeolog. Journal," Vol.
VI. p. 27). Transl.]
[131] "Chemiker Zeitung," XI. 1887, p. 605.
[132] Ant. Fr. 1154 _a_.
[133] I should now use paraffin for impregnation. (Author's note.)
[134] [Great caution must be used to prevent inhalation of the gas, which
is extremely poisonous. Transl.]
[135] Instead of potassium cyanide, I have made experimental use of the
much more readily fusible potassium sulphocyanide. This converts the iron
compounds into iron sulphide, which is easily got rid of. The sulphide
which still adheres to the iron and imparts a not unpleasing blackish
colour to the object appears to be stable.
The rest of the treatment is similar to that above described. Having so
far only experimented with a few specimens I am not yet in a position
to offer any judgment as to the practicability of the process. (Author,
1904.) [For practical objections to this method, which we do not consider
satisfactory owing to the instability of the products resulting from the
reaction, and the difficulty in removing them by the subsequent washing,
see Milbauer, "Zeit. f. anorg. Chem." XLII. 1904, p. 433 ("Journ. Chem.
Soc." Abstracts, i. 121), where it is stated that treatment of Fe_{2}O_{3}
at 400°C. leads to the formation of K_{2}Fe_{2}S_{4}. Transl.]
[136] Stolba, "Chemiker Zeitung," XX. 1896, Repertorium, p. 240. [Sodium
sulphide has a very deleterious action upon the skin and fingernails which
should be protected when using this substance. Transl.]
[137] Flinders Petrie, "Archaeological Journal," Vol. XLV. 1888, p. 88.
[138] Cp. Mugdan, "Zeit. Elektrochem." 1903, ix. p. 442.
[139] [A method used by the explorers of the Palestine Exploration
Committee for the preservation of much decayed bronzes, as, for instance,
those from wells and cisterns, is to place them immediately they are
discovered into a strong solution (1 in 10) of carbolic acid. Transl.]
[140] "Merkbuch," p. 68.
[141] Instead of calcium chloride strong sulphuric acid may be used for
dehydration, but the dry chloride is more simple, and less dangerous. If
kept in corked bottles, the corks should be covered with paraffin wax to
prevent access of moisture.
[142] First put forward by Chevreul (see pp. 22 and 117).
[143] [The so-called 'pole paper' is supplied by most dealers in
electrical apparatus. Transl.]
[144] In such a case the hydrated oxide of tin is either present as
such in the oxidized bronze, or it is a product of the reduction which
has been prevented from falling to the bottom by the high sp. gr. of
the potassium cyanide solution. It is also possible that finely divided
tin in the reduced bronze may decompose the warm water into oxygen and
hydrogen, forming a hydrated oxide of tin. Such a reaction would account
for the formation of hydrogen. The hydrogen might at the same time remain
occluded until allowed to separate by the cessation of the current and
the temperature of the water.
[145] Such, for instance, as is obtained by attaching a suitable nozzle to
a fall pipe where there is sufficient water-pressure; v. e.g. "Polytechn.
Centralblatt," 1891-92, p. 199.
[146] I now consider it a better plan not to employ the method of coating
with paraffin wax. I thoroughly soak and then dry the reduced bronze with
a cloth, and place it in 96% alcohol. This must be renewed after a time,
and for large bronzes a third or even a fourth renewal is advisable. The
bronze is again wiped and introduced into a drying oven raised to about
212°F. [100°C.]. The unsightly grey colour and rough surface may be much
improved by using a brush of the finest wire or very fine emery cloth. The
object is finally impregnated with zapon (see Appendix). (Author's note,
1904.)
[147] [The base was not treated owing to the advanced destruction of the
metal. Transl.]
[148] In only about 2% of the bronzes treated in the laboratory of the
Royal Museums at Berlin has it been found necessary to interrupt the
reduction.
[149] "Polytechn. Centralblatt," 1891-92, p. 200.
[150] These analyses were made by Schulz in the Laboratory of the Royal
Museums.
[151] I quote here the greater part of an article published in Dingler's
"Polytechn. Journal," 1896, Vol. CCCI. p. 44. The reduction of about 7000
Danish copper coins, undertaken while the above was in the press, gave
similarly good results.
[152] The zinc, which in the course of the reduction process may become
coated with a thin layer of metallic copper, may be used again. It should
be first put through dilute sulphuric acid (in the proportion of 1:2),
then washed, rubbed with a steel wire brush and again washed. But it must
in such cases be used again while still wet, for if allowed to dry it
becomes coated with a layer of oxide and requires to be re-polished.
[153] "Publications de la société pour la recherche et la conservation des
monuments historiques dans le grandduché de Luxembourg," Vol. X. As I have
been unable to consult the original, I have here inserted a communication
sent to me by Dr Kisa of Cologne. I have tried this method on a few coins.
[154] In another instance--that of a Minotaur group [Ant. Misc. 7382]--the
calcium chloride is contained in four shallow glass troughs which are
placed round the marble pedestal of the bronze and are loosely covered
with a black card.
[155] Grote, "Blätter für Münzkunde," 1835, I. No. 31, VI.
[156] "Zeitschrift für Numismatik," Vol. XVII. 1890, p. 100.
[157] "Prometheus," VIII. 1897, p. 351. A report on the other methods is
here given.
[158] "Zeitschrift für Numismatik," Vol. XX. 1897, p. 325.
[159] "Archaeological Journal," XLV. 1888, p. 87.
[160] "Riv. Ital. Numism." 1903, p. 31; also "Chemiker Zeitung," XXVII.
1903, p. 825.
[161] [In this connection however it must be remembered that celluloid
gives off traces of acid for a long time. This may possibly involve risk
of injury to certain specimens. Transl.]
[162] "Mittheilungen des Nordböhmischen Gewerbe Museum," 1903, p. 104.
[163] [A few drops of formalin will serve the same purpose. Transl.]
[164] [Lanoline, especially if applied warm, retains the flexibility of
the leather very satisfactorily. It may be here mentioned that the leather
of old book-bindings may be preserved by the application, by means of
a soft brush, of a mixture of white wax with a small quantity of white
vaseline and paraffin wax, brought to a pasty consistency with benzine or
turpentine.
The 'Stearine Glaze' used for the same purpose is made by boiling one part
of caustic soda with eight parts of stearic acid and 50 parts of water
till dissolved, then mixing another 150 parts of cold water and stirring
until the whole sets to a jelly.
Either of these media should be applied very thinly and then polished with
a brush or flannel. If the cover is very bad, considerable improvement
is effected by repeated applications of the stearine glaze so as to fill
up the damaged surface of the leather. In some cases the addition of
some dye such as logwood, or one or other of the acid coal-tar dyes, is
advantageous.
Lanoline, or wool fat, i.e. lanoline without the water, is useful, but
gives a dull surface to the leather.
In some cases a thin coating of diluted white of egg, to which a few drops
of clove oil, or some other essential oil, has been added as an antiseptic
is beneficial. Transl.]
[165] On preservation in alcohol see p. 159 under the heading 'Wood.'
[166] "Aarb. for nordisk Oldkynd. og Historie," 1891, p. 112.
[167] According to an analysis published by L. v. Barth in an account of
the collection of papyri belonging to the Archduke Rainer, Part I. p. 120,
the salt crystals, after removal of the insoluble constituents, consisted
of:
Potassium sulphate 0·8%
Potassium and sodium chlorides 92·0%
Calcium sulphate 4·6%
Magnesium chloride 2·8%
Organic substances 0·2%
[168] "Merkbuch," p. 60.
[169] Communicated by Herr Leiner of Constance.
[170] "Antiquarisk Tidsskrift," 1858-60, p. 176.
[171] Id., p. 174.
[172] Olshausen, "Verh. der Berl. anthropol. Ges." 1885, p. 242, an oral
communication from Herr v. Jenner.
[173] Attention may be drawn to a paper which (Dec. 1904) will shortly be
published by the Imperial Commission for Monuments of Art and History in
Vienna. At a meeting in Vienna a paper was given by Bolle on the animal
enemies of paper, leather, and wood, and their destruction by means of
carbon bisulphide. Carbon bisulphide is an infallible poison and has
no effect upon colours when used in a perfectly dry state. This may be
carried out by a preliminary displacement of the air by carbonic acid
which is readily obtained in the liquid form in cylinders. Benzine would
probably act equally well, but would require a longer time for its action.
References to other methods such as the employment of a vacuum or of heat
will be found in the same publication.
[174] Keim, "Technische Mittheilungen für Malerei," 1888, p. 4.
[175] Communication from Herr Straberger of Linz on the Danube.
[176] Communication by Dr Voss.