I do not here mean to enter into the history of engraving on stone,
as that subject has been already sufficiently illustrated by several
men of learning well acquainted with antiquities. I shall only
observe, that the ancient Greek artists formed upon glass both raised
and engraved figures; as may be seen by articles still preserved in
collections, though it is probable that many pieces of glass may
have been moulded like paste; for that art also is of very great
antiquity[204]. It appears likewise that they cut upon plates of
glass and hollow glass vessels all kinds of figures and ornaments,
in the same manner as names, coats of arms, flowers, landscapes, &c.
are cut upon drinking-glasses at present[205]. If we can believe that
learned engraver in stone, the celebrated Natter, the ancients employed
the same kind of instruments for this purpose as those used by the
moderns[206]. They undoubtedly had in like manner a wheel which moved
round in a horizontal direction above the work-table, or that machine
which by writers is called a lapidary’s wheel.
If this conjecture be true, what Pliny says respecting the various
ways of preparing glass is perfectly intelligible. It is turned, says
he, by the wheel, and engraven like silver. In my opinion we are to
understand by the first part of this sentence, that the glass was
cut by the wheel, like stone, both hollow and in relief, though it
is possible that drinking-cups or vessels may have been formed from
the glass metal by means of the wheel also[207]. In the latter part
of the sentence we must not imagine that Pliny alludes to gravers
like those used by silversmiths, for the comparison will not apply to
instruments or to the manner of working, which in silver and glass must
be totally different; but to the figures delineated on the former,
which were only cut out on the surface in a shallow manner; and such
figures were formed on glass by the ancient artists, as they are by our
glass-cutters, by means of a wheel.
Many, however, affirm that the art of glass-cutting, together with
the necessary instruments, was first invented in the beginning of the
seventeenth century. The inventor is said to have been Casper Lehmann,
who originally was a cutter of steel and iron; and who made an attempt,
which succeeded, of cutting crystal, and afterwards glass, in the like
manner. He was in the service of the emperor Rodolphus II., who, in the
year 1609, besides presents, conferred on him the title of lapidary and
glass-cutter to the court, and gave him a patent by which every one
except himself was forbidden to exercise this new art. He worked at
Prague, where he had an assistant named Zacharias Belzer; but George
Schwanhard the elder, one of his scholars, carried on the same business
to a far greater extent. The latter, who was a son of Hans Schwanhard,
a joiner at Rothenburg, was born in 1601; and in 1618 went to Prague to
learn the art of glass-cutting from Lehmann. By his good behaviour he
so much gained the esteem of his master, who died a bachelor in 1622,
that he was left his heir; and obtained from the emperor Rodolphus
a continuation of Lehmann’s patent. Schwanhard, however, removed to
Nuremberg, where he worked for many of the principal nobility; and by
these means procured to that city the honour of being accounted the
birth-place of this new art. In the year 1652 he worked at Prague and
Ratisbon by command of the emperor Ferdinand III., and died in 1667,
leaving behind him two sons, who both followed the occupation of the
father. The elder, who had the same christian name as the father, died
so early as 1676; but the other, Henry, survived him several years.
After that period Nuremberg produced in this art more expert masters,
who, by improving the tools and devising cheaper methods of employing
them, brought it to a much higher degree of perfection[208].
That the art is of so modern date seems to be confirmed by Zahn,
who speaks of it as of a new employment carried on at that time,
particularly at Nuremberg. He describes the work-table as well as the
other instruments; and gives a figure of the whole, which he appears
to have considered as the first[209]. It may be seen, however, from
what I have already quoted, that this invention does not belong
entirely to the moderns; and, to deny that the ancients were altogether
unacquainted with it, would be doing them an injustice. It was
forgotten and again revived; and this is the opinion of Caylus.
I must here remark, that before this invention there were artists,
who, with a diamond, cut or engraved figures on glass, which were
everywhere admired. Without entering, however, into the history of
diamonds, which would require more materials than I have yet been able
to collect, I will venture to assert that the ancient artists employed
diamond dust for polishing or cutting other kinds of stones. Pliny[210]
speaks of this in so clear a manner that it cannot be doubted. The same
thing has been repeated by Solinus[211], Isidore[212], and Albertus
Magnus[213], in a manner equally clear, and Mariette[214] considers
it as fully proved; but it does not appear that the ancients made any
attempts to cut this precious stone with its own dust; I mean to give
it different faces and to render it brilliant. Whether they engraved on
it in that manner I cannot pretend to decide, as the greatest artists
are not agreed on the subject. Mariette[215] denies that they did;
whereas Natter[216] seems not to deny it altogether, and Klotz[217]
confidently asserts it as a thing certain. But the last-mentioned
author knew nothing more of this circumstance than what he had read in
the above-quoted writers.
The question which properly belongs to my subject is, whether the
Greeks and the Romans used diamond pencils for engraving on other
stones. That many ancient artists assisted their labour by them, or
gave their work the finishing touches, seems, according to Natter,
to be shown by various antique gems. But even allowing this to have
been the case (for at any rate I dare not contradict so eminent a
connoisseur), I must confess that I have found no proofs that the
ancients cut glass with a diamond. We are however acquainted with the
means employed by the old glaziers to cut glass: they used for that
purpose emery, sharp-pointed instruments of the hardest steel, and
a red-hot iron, by which they directed the rents according to their
pleasure.
The first mention of a diamond being used for writing on glass occurs
in the sixteenth century. Francis I. of France, who was fond of the
arts, sciences, and new inventions, wrote the following lines with his
diamond ring upon a pane of glass, at the castle of Chambord, in order
to let Anne de Pisseleu, duchess of Estampes, know that he was jealous:
Souvent femme varie,
Mal habil qui s’y fie.
The historian recorded this not so much on account of the admonition,
which is not new, as because it was then thought very ingenious
to write upon glass[218]. About the year 1562, festoons and other
ornaments, cut with a diamond, were extremely common on Venetian
glasses, which at that period were accounted the best. George
Schwanhard the elder was a great master in this art[219]; and in more
modern times, John Rost, an artist of Augsburg, ornamented in a very
curious manner with a diamond pencil, some drinking-glasses which were
purchased by the emperor Charles VI.
I now come to the art of etching on glass, which properly was the
subject of this article. As the acid which dissolves siliceous earth,
and also glass, was first discovered in the year 1771, by Scheele
the chemist[220], in fluor-spar, one might imagine that the art of
engraving with it upon glass could not be older. It has indeed been
announced by many as a new invention[221]; but it can be proved that
it was discovered as early as the year 1670, by the before-mentioned
artist Henry Schwanhard. We are told that some aquafortis having fallen
by accident upon his spectacles, the glass was corroded by it; and
that he thence learned to make a liquid by which he could etch writing
and figures upon plates of glass[222]. How Schwanhard prepared this
liquid I find nowhere mentioned; but at present we are acquainted with
no other acid but that of fluor-spar which will corrode every kind of
glass; and it is very probable that his preparation was the same as
that known to some artists as a secret in 1721. The inventor however
employed it to a purpose different from that for which it is used at
present.
At present the glass is covered with a varnish, and those figures which
one intends to etch are traced out through it; but Schwanhard, when the
figures were formed, covered them with varnish, and then by his liquid
corroded the glass around them; so that the figures, which remained
smooth and clear, appeared when the varnish was removed, raised from a
dim or dark ground. He perhaps adopted this method in order to render
his invention different from the art known long before of cutting the
figures on the glass as if engraven. Had he been able to investigate
properly what accident presented to him, he might have enriched the
arts with a discovery which gave great reputation to a chemist a
hundred years after.
I mentioned this old method of etching in relief to our ingenious
Klindworth, who possesses great dexterity in such arts, and requested
him to try it. He drew a tree with oil varnish and colours on a plate
of glass, applied the acid to the plate in the usual manner, and
then removed the varnish. By these means a bright, smooth figure was
produced upon a dim ground, which had a much better effect than those
figures that are cut into the glass. I recommend this process, because
I am of opinion that it may be brought to much greater perfection; and
M. Renard, that celebrated artist of Strasburg, whose thermometers with
glass scales, in which the degrees and numbers are etched, have met
with universal approbation, was of the same opinion, when I mentioned
the method to him while he resided here, banished from his home by the
disturbances in his native country.
It is probable that Schwanhard and his scholars kept the preparation
of this liquid a secret, as the receipt for that purpose was not
made known till the year 1725, though it is possible that one older
may be found in some of those books which treat on the arts. In the
above-mentioned year, Dr. John George Weygand, from Goldingen in
Courland, sent to the editor of a periodical work a receipt which had
been written out for him by Dr. Matth. Pauli of Dresden, then deceased,
who had etched, in this manner on glass, arms, landscapes, and figures
of various kinds[223]. We find by it that a strong acid of nitre was
used, which certainly disengages the acid of fluor-spar, though the
vitriolic acid is commonly employed for that purpose[224]. That the
Bohemian emerald or _hesphorus_, mentioned in the receipt, is green
fluor-spar, cannot be doubted, and will appear still more certain from
the history of this species of stone, as far as I am acquainted with
it, which I shall here insert.
In the works of the old mineralogists, fluor-spar is either not
mentioned, or is classed among their natural glasses and precious
stones; and in those of the first systematic writers it is so mingled
with quartz and calcareous and gypseous spars, that it is impossible to
discover it. The old German miners, however, distinguished it so early
as the sixteenth century, and called it _fluss_; because they used it
to accelerate the fusion of ores that were difficult to be reduced to
that state. Agricola, who first remarked this, changed the German name
into _fluor_, an appellation, which, like many others, formed by him
from German words, such for example as _quarzum_ from _quarz_, _spatum_
from _spat_, _wismuthum_, _zincum_, _cobaltum_, &c., became afterwards
common. If a passage of the ancients can be quoted that seems to allude
to fluor-spar, it is that of Theophrastus, where he says that there
are certain stones which, when added to silver, copper, and iron ores,
become fluid[225]. The first systematic writer who mentioned this kind
of stone as a particular genus, was Cronstedt.
Besides being known by its metallurgic use, fluor-spar is known also
by having the colours of some precious stones, so that it may be sold,
or at least shown as such to those who are not expert judges; because
the first time when heated in the dark it shines with a bluish-green
lustre. It is possible that fluor-spar may have been among the
number of that great variety of stones which the ancients, with much
astonishment, tell us shone in the dark; though it is certain that the
principal part of them were only light-magnets, as they are called, or
such as retain for a certain period the light they have absorbed in the
day-time. The observation, however, that fluor-spar emits light after
it is heated, seems to have been first made when artificial phosphorus
excited the inquiry of naturalists and chemists; and when they began
to search in their own country for stones which, in the property of
emitting light, might have a resemblance to the Bologna spar, made
known about the year 1630. It is well known that the latter is prepared
for that purpose by calcination. Stones of the like kind were sought
for; and among these fluor-spar, which is not scarce in Germany.
In my opinion, the observation was made in the year 1676; for in that
year Elsholz informed the members of the Society for investigating
Nature, that he was acquainted with a phosphorus which had its light
neither from the sun nor from fire, but which, when heated on a metal
plate over glowing coals, shone with a bluish-white lustre; so that by
strewing the powder of it over paper, one might form luminous writing.
I doubt much whether this experiment was ever tried; at least I find
no further account of it in the papers of the Society, nor in the
re-publication of the above author’s first dissertation, which appeared
in 1681[226].
As far as I know, Kirchmaier, professor at Wittenberg, was the first
who disclosed the secret, in the year 1679[227]. Both call this
phosphorus the smaragdine; because the ancients speak much of luminous
emeralds, and because green fluor-spar is often exhibited as an
emerald. Kirchmaier calls this mineral also _hesperus_ and _vesperugo_;
and these names have been often given since to fluor-spar, as in
the receipt before-mentioned for making a liquid to etch on glass.
Kirchmaier’s information, however, must have been very little known;
for the Jesuit Casatus, who, in 1684, wrote his Treatise on Fire, was
not acquainted with it, as he has inserted only the words of Elsholz.
This observation must have been new to Leibnitz himself, and to the
Academy of Sciences at Berlin, in 1710; for the former then mentioned
it to the Society as a philosophical novelty[228].
I shall remark, in the last place, that the manufacturing of vessels
and ornaments of every kind from solid fluor-spar was begun in
Derbyshire in the year 1765[229]. The articles formed of it are
in England called spar ornaments, and sometimes _blue John_. Many
beautiful colours must, as is said, be brought forward by means of
fire. But the heat must be applied with great caution; for fluor-spar,
as is well known, by a strong and particularly a sudden heating,
cracks, and loses its transparency. Since writing the above, I find
that M. Raspe[230] denies this bringing forward of colours by fire.