pattern letters and figures and similar small parts of brass, iron,
or plaster molds, is made of lead 80 parts, and antimony 20 parts. A
better alloy will be lead 70 parts, antimony and bismuth each 15 parts.
To insure perfect work the molds should be quite hot by placing them
over a Bunsen burner.
«Alloy for Caliper and Gage-Rod Castings.»—A mixture of 30 parts zinc
to 70 parts aluminum gives a light and durable alloy for gage rods and
caliper legs; the gage rods must be steel tipped, for the alloy is soft
and wears away too rapidly for gage points.
«Alloys for Small Casting Molds.»—Tin, 75 parts, and lead, 22 parts;
or 75 parts of zinc and 25 parts of tin; or 30 parts of tin and 70
parts of lead; or 60 parts of lead and 40 parts of bismuth.
ALLOYS FOR METAL FOIL: See Metal Foil.
ALMOND COLD CREAM: See Cosmetics.
ALMOND LIQUEURS: See Wines and Liquors.
ALTARS, TO CLEAN: See Cleaning Preparations and Methods.
«ALUM:»
«Burnt Alum.»—I.—Heat the alum in a porcelain dish or other suitable
vessel till it liquefies, then raise and continue the heat, not
allowing it to exceed 400°, till aqueous vapor ceases to be disengaged,
and the salt has lost 47 per cent of its weight. Reduce the residue to
powder, and preserve it in a well-stoppered bottle.—_Cooley._
II.—Heat ordinary alum (alumina alum) with constant stirring in an iron
pan in which it will first melt quietly, and then commence to form
blisters. Continue heating until a dry white mass of a loose character
remains, which is powdered and kept in well-closed glasses.
ALUM BATH: See Photography.
«Aluminum and its Treatment»
«HOW TO COLOR ALUMINUM:»
«Blanching of Aluminum.»—Aluminum is one of the metals most inalterable
by air; nevertheless, the objects of aluminum tarnish quickly enough
without being {81} altered. They may be restored to their mat whiteness
in the following manner: Immerse the aluminum articles in a boiling
bath of caustic potash; next plunge them quickly into nitric acid,
rinse and let dry. It must be understood that this method is applicable
only to pieces entirely of aluminum.
«Decolorized Aluminum.»—Gray or unsightly aluminum may be restored
to its white color by washing with a mixture of 30 parts of borax
dissolved in 1,000 parts of water, with a few drops of ammonia added.
«Mat Aluminum.»—In order to impart to aluminum the appearance of mat
silver, plunge the article into a hot bath composed of a 10-per-cent
solution of caustic soda saturated with kitchen salt. Leave it in the
bath for 15 to 20 seconds, then wash and brush; put back into the bath
for half a minute, wash anew and dry in sawdust.
«To Blacken Aluminum.»—I.—The surface of the sheet to be colored is
polished with very fine emery powder or finest emery cloth. After
polishing pour a thin layer of olive oil over the surface and heat
slowly over an alcohol flame. Large sheets must, of course, be heated
in the drying oven. After a short while pour on oil again, in order
to obtain absolute uniformity of the coating, and heat the plate once
more. Under the action of the heat the plate turns first brown, then
black, according to the degrees of heat. When the desired coloration
has been attained, the plate is polished over again, after cooling,
with a woolen rag or soft leather.
II.—White arsenic 1 ounce
Sulphate of iron 1 ounce
Hydrochloric acid 12 ounces
Water 12 ounces
When the arsenic and iron are dissolved by the acid add the water.
The aluminum to be blackened should be well cleaned with fine emery
powder and washed before immersing in the blackening solution. When the
deposit of black is deep enough dry off with fine sawdust and lacquer.
«Decorating Aluminum.»—A process for decorating aluminum, patented
in Germany, prescribes that the objects be first corroded, which is
usually done with caustic soda lye, or, better still, by a new method
which consists in heating 3 parts of sulphuric acid with 1 part of
water to 140° to 158° F., in an enameled vessel. Into this liquid dip
the aluminum articles, rinsing them off clean and then drying them
well. The corroded articles are now placed in a bath consisting of
1,000 parts of alcohol (90 per cent), 1.50 parts of antimony, 250 parts
of chemically pure hydrochloric acid, 100 parts of manganous nitrate,
and 20 parts of purified and finely elutriated graphite. In this bath,
which is heated to 86°–95° F., the objects are left until fumes develop
around them, which takes place in a few seconds. Now they are put over
a coal fire or similar arrangement until the alcohol is burned up
and there is no more smoke. After they are somewhat cooled off, they
are laid into cold water and worked with a brush, then rinsed with
water and well dried. The pieces are now provided with a gray metallic
coating, consisting mainly of antimony, manganese, and graphite. This
metallic layer renders them capable of receiving a lacquer which is
best prepared from 1,000 parts of alcohol (90 per cent), 50 parts of
sandarac, 100 parts of shellac, and 100 parts of nigrosine (black
aniline color). Then the articles are quickly but thoroughly rinsed
off, dried in warmed air for a few minutes, and baked in ovens or over
a moderate coal fire until they do not smoke any more and no more gloss
can be seen. Finally they are rubbed with a cotton rag saturated with
thin linseed-oil varnish, and the objects thus treated now appear dull
black, like velvet. The covering withstands all action of the weather,
so that cooking vessels coated with this varnish on the outside can
be placed on the fire without injury to the coating. If the articles
are engraved, the aluminum appears almost glossy white under the black
layer at the engraved places. When the pieces have been provided with
the gray metallic coating, colored lacquer may also be applied with the
brush. In this manner paintings, etc., may be done on aluminum, while
not possible on unprepared aluminum surfaces, which will not retain
them.
«Making Castings in Aluminum.»—The method adopted in preparing molds
and cores for aluminum work is necessarily somewhat the same as for
brass, but there are particular points which need attention to insure
successful work. Both in the sand and the making of the molds there
are some small differences which make considerable variation in
the results, and the temperature at which the metal is poured is a
consideration of some importance.
In selecting the sand, which should {82} not have been previously used,
that of a fine grain should be chosen, but it should not have any
excess of aluminous matter, or it will not permit of the free escape of
gases and air, this being an important matter. Besides this, the sand
must be used as dry as possible consistent with its holding against the
flow of the metal, and having only moderate compression in ramming.
In making the molds it is necessary to remember that aluminum has a
large contraction in cooling, and also that at certain temperatures
it is very weak and tears readily, while all metals shrink away from
the mold when this is wholly outside the casting, but they shrink on
to cores or portions of the mold partly inclosed by metal. Thus, if
casting a plate or bar of metal, it will shrink away from the mold in
all directions; but if casting a square frame, it shrinks away from
the outside only, while it shrinks on to the central part or core.
With brass, or iron, or such metals, this is not of much importance,
but with some others, including aluminum, it is of great importance,
because if the core or inclosed sand will not give somewhat with the
contraction of the metal, torn or fractured castings will be the
result. Both for outside and inside molds, and with cores used with
aluminum, the sand should be compressed as little as possible, and
hard ramming must in every case be avoided, particularly where the
metal surrounds the sand. The molds must be very freely vented, and
not only at the joint of the mold, but by using the vent wire freely
through the body of the mold itself; in fact, for brass the venting
would be considered excessive. With aluminum it is, however, necessary
to get the air off as rapidly as possible, because the metal soon gets
sluggish in the mold, and unless it runs up quickly it runs faint
at the edges. The ingates should be wide and of fair area, but need
careful making to prevent their drawing where they enter the casting,
the method of doing this being known to most molders.
If it is considered desirable to use a specially made-up facing sand
for the molds where the metal is of some thickness, the use of a little
pea or bean meal will be all that is necessary. To use this, first
dry as much sand as may be required and pass through a 20-mesh sieve,
and to each bushel of the fine sand rub in about 4 quarts of meal,
afterwards again passing through the sieve to insure regular mixing.
This sand should then be damped as required, being careful that all
parts are equally moist, rubbing on a board being a good way to get it
tough, and in good condition, with the minimum of moisture.
The molds should not be sleeked with tools, but they may be dusted
over with plumbago or steatite, smoothing with a camel’s-hair brush,
in cases in which a very smooth face is required on the castings.
Preferably, however, the use of the brush even should be avoided.
Patterns for aluminum should be kept smooth and well varnished.
In melting the metal it is necessary to use a plumbago crucible which
is clean and which has not been used for other metals. Clay or silica
crucibles are not good for this metal, especially silica, on account
of the metal absorbing silicon and becoming hard under some conditions
of melting. A steady fire is necessary, and the fuel should reach only
about halfway up the crucible, as it is not desirable to overheat the
crucible or metal. The metal absorbs heat for some time and then fuses
with some rapidity, hence the desirability of a steady heat; and as the
metal should be poured when of a claret color under the film of oxide
which forms on the surface, too rapid a heating is not advisable. The
molding should always be well in advance of the pouring, because the
metal should be used as soon as it is ready; for not only is waste
caused, but the metal loses condition if kept in a molten state for
long periods. The metal should be poured rapidly, but steadily, and
when cast up there should not be a large head of metal left on top of
the runner. In fact, it is rather a disadvantage to leave a large head,
as this tends to draw rather than to feed the casting.
With properly prepared molds, and careful melting, fluxes are not
required, but ground cryolite—a fluoride of sodium and aluminum—is
sometimes used to increase the fluidity of the metal. In using this, a
few ounces according to the bulk of metal to be treated is put into the
molten metal before it is taken from the furnace, and well stirred in,
and as soon as the reaction apparently ceases the pot is lifted and the
metal at once skimmed and poured. The use of sodium in any form with
aluminum is very undesirable, however, and should be avoided, and the
same remark applies to tin, but there is no objection to alloying with
zinc, when the metal thus produced is sold as an alloy.
Aluminum also casts very well in molds of plaster of Paris and crushed
bath brick when such molds are perfectly dry {83} and well vented,
smoothness being secured by brushing over with dry steatite or
plumbago. When casting in metal molds, these should be well brushed out
with steatite or plumbago, and made fairly hot before pouring, as in
cold molds the metal curdles and becomes sluggish, with the result that
the castings run up faint.
«To Increase the Toughness, Density, and Tenacity of Aluminum.»—For the
purpose of improving aluminum, without increasing its specific gravity,
the aluminum is mixed with 4 to 7 per cent of phosphorus, whereby the
density, tenacity, and especially the toughness are said to be enhanced.
«WORKING OF SHEET ALUMINUM:»
The great secret, if there is any, in working aluminum, either pure or
alloyed, consists in the proper lubricant and the shape of the tool.
Another great disadvantage in the proper working of the metal is that,
when a manufacturer desires to make up an article, he will procure the
pure metal in order to make his samples, which, of course, is harder to
work than the alloy. But the different grades of aluminum sheet which
are on the market are so numerous for different classes of work that it
might be advisable to consider them for a moment before passing to the
method of working them.
The pure metal, to begin with, can be purchased of all degrees of
hardness, from the annealed, or what is known as the “dead soft”
stock, to the pure aluminum hard rolled. Then comes a harder grade of
alloys, running from “dead soft” metal, which will draw up hard, to
the same metal hard rolled; and, still again, another set of alloys
which, perhaps, are a little harder still when hard rolled, and will,
when starting with the “dead soft,” spin up into a utensil which, when
finished, will probably be as stiff as brass. These latter alloys
are finding a large sale for replacing brass used in all classes of
manufactured articles.
To start with lathe work on aluminum, probably more difficulty has been
found here, especially in working pure metal, and more complaints are
heard from this source than from any other. As stated before, however,
these difficulties can all be readily overcome, if the proper tools
and the proper lubricants are used, as automatic screw machines are
now made so that they can be operated when working aluminum just as
readily as when they are working brass, and in some cases more readily.
To start with the question of the tool, this should be made as what is
known as a “shearing tool,” that is, instead of a short, stubby point,
such as would be used in turning brass, the point should be lengthened
out and a lot of clearance provided on the inside of the tool, so as
to give the chips of the metal a good chance to free themselves and
not cause a clogging around the point of the tool—a similar tool, for
instance, to what would be used for turning wood.
The best lubricant to be used would be coal oil or water, and plenty of
it. The latter is almost as good as coal oil if enough of it is used,
and with either of these lubricants and a tool properly made, there
should be no difficulty whatsoever in the rapid working of aluminum,
either on the lathe or on automatic screw machines.
To go from the lathe to the drawing press, the same tools here would
be used in drawing up shapes of aluminum as are used for drawing up
brass or other metals; the only precaution necessary in this instance
being to use a proper lubricant, which in this case is a cheap grade of
vaseline, or in some cases lard oil, but in the majority of instances
better results will be secured by the use of vaseline. Aluminum is
probably susceptible of deeper drawing with less occasion to anneal
than any of the other commercial metals. It requires but one-third or
one-fourth of as much annealing as brass or copper. For instance, an
article which is now manufactured in brass, requiring, say, three or
four operations before the article is finished, would probably have
to be annealed after every operation. With aluminum, however, if the
proper grade is used, it is generally possible to perform these three
operations without annealing the metal at all, and at the same time to
produce a finished article which, to all intents and purposes, is as
stiff as an article made of sheet brass.
Too much stress cannot be laid on the fact of starting with the proper
grade of metal, for either through ignorance or by not observing this
point is the foundation of the majority of the complaints that aluminum
“has been tried and found wanting.” If, however, it should be found
necessary to anneal aluminum, this can be readily accomplished by
heating it in an ordinary muffle, being careful that the temperature
shall not be too high—about 650° or 700° F. The best test as to when
the metal has reached the proper temperature is to take a soft pine
stick and draw it across the {84} metal. If it chars the stick and
leaves a black mark on the metal, it is sufficiently annealed and is in
a proper condition to proceed with further operation.
Next taking up the question of spinning aluminum, success again
depends particularly on starting with the proper metal. The most
satisfactory speed for articles from 5 to 8 inches in diameter is
about 2,600 revolutions a minute, and for larger or smaller diameters
the speed should be so regulated as to give the same velocity at the
circumference. Aluminum is a very easy metal to spin and no difficulty
should be found at all in spinning the proper grades of sheets.
Several factories that are using large quantities of aluminum now, both
for spinning and stamping, are paying their men by the piece the same
amount that they formerly paid on brass and tin work, and it is stated
that the men working on this basis make anywhere from 10 to 20 per cent
more wages by working aluminum.
After aluminum has been manufactured into the shape of an article, the
next process is the finishing of it. The best polish can be obtained
by first cutting down the metal with an ordinary rag buff on which
use tripoli, and then finish it with a dry red rouge which comes in
the lump form, or that which is known as “White Diamond Rouge.” One
point, however, that it is necessary to observe carefully is that both
the tripoli and the rouge should be procured ground as fine as it is
possible to grind them; for, if this is not done, the metal will have
little fine scratches all over it, and will not appear as bright and as
handsome as it otherwise would.
If it is desired to put on a frosted appearance, this can either
be done by scratch brushing or sand blasting. A brass wire scratch
brush, made of crimped wire of No. 32 to No. 36 B. & S. gage, with
three or four rows of bristles, will probably give the best results.
This work of scratch brushing can be somewhat lessened, however, if,
before applying the scratch brush to the surface of the aluminum, the
article is first cut down by the use of a porpoise-hide wheel and fine
Connecticut sand, placing the sand between the surface of the aluminum
and the wheel, so that the skin and the irregularities on the surface
are removed, and then putting the article on a buffing wheel before
attempting to scratch brush it. This method, however, is probably more
advantageous in the treating of aluminum castings than for articles
manufactured out of the sheet metal, as in the majority of cases it is
simply necessary before scratch brushing to cut down the article with
tripoli, and then polish it with rouge as already described, before
putting on the scratch brush; in this way the brush seems to take hold
quicker and better, and to produce a more uniform polish.
An effect similar to the scratch-brush finish can be got by sand
blasting, and by first sand blasting and then scratch brushing the
sheets, a good finish is obtained with very much less labor than by
scratch brushing alone. Another very pretty frosted effect is procured
by first sand blasting and then treated as hereinafter described
by “dipping” and “frosting,” and many variations in the finish of
aluminum can be got by varying the treatment, either by cutting
down with tripoli and polishing, scratch brushing, sand blasting,
dipping, and frosting, and by combinations of those treatments. A very
pretty mottled effect is secured on aluminum by first polishing and
then scratch brushing and then holding the aluminum against a soft
pine wheel, run at a high rate of speed on a lathe, and by careful
manipulation, quite regular forms of a mottled appearance can be
obtained.
The dipping and frosting of aluminum sheet is probably the cheapest way
of producing a nice finish. First remove all grease and dirt from the
article by dipping in benzine, then dip into water in order that the
benzine adhering to the article may be removed, so as not to affect
the strength of the solution into which it is next dipped. After they
have been taken out of the water and well shaken, the articles should
be plunged in a strong solution of caustic soda or caustic potash,
and left there a sufficient length of time until the aluminum starts
to turn black. Then they should be removed, dipped in water again,
and then into a solution of concentrated nitric and sulphuric acid,
composed of 24 parts of nitric acid to 1 part of sulphuric acid. After
being removed, the article should be washed thoroughly in water and
dried in hot sawdust in the usual way. This finish can also be varied
somewhat by making the solution of caustic soda of varying degrees of
strength, or by adding a small amount of common salt to the solution.
In burnishing the metal use a bloodstone or a steel burnisher. In
burnishing use a mixture of melted vaseline and coal oil, or a solution
composed of 2 tablespoonfuls of ground borax dissolved in about a quart
of hot water, with a few {85} drops of ammonia added. In engraving,
which adds materially to the appearance of finished castings, book
covers, picture frames, and similar articles made of sheet, probably
the best lubricant to use on an engraver’s tool in order to obtain a
clean cut, which is bright, is naphtha or coal oil, or a mixture of
coal oil and vaseline. The naphtha, however, is preferred, owing to the
fact that it does not destroy the satin finish in the neighborhood of
the cut, as the other lubricants are very apt to do. There is, however,
as much skill required in using and making a tool in order to give a
bright, clean cut as there is in the choice of the lubricant to be
used. The tool should be made somewhat on the same plan as the lathe
tools already outlined. That is, they should be brought to a sharp
point and be “cut back” rather far, so as to give plenty of clearance.
There has been one class of work in aluminum that has been developed
lately and only to a certain extent, in which there are great
possibilities, and that is in drop forging the metal. Some very
superior bicycle parts have been manufactured by drop forging. This can
be accomplished probably more readily with aluminum than with other
metals, for the reason that it is not necessary with all the alloys
to work them hot; consequently, they can be worked and handled more
rapidly.
ALUMINUM, TO CLEAN: See Cleaning Preparations and Methods.
ALUMINUM ALLOYS: See Alloys.
ALUMINUM BRONZE: See Alloys under Bronzes.
ALUMINUM CASTINGS: See Casting.
ALUMINUM PAPER: See Paper.
ALUMINUM PLATING: See Plating.
ALUMINUM POLISHES: See Polishes.
«Amalgams»
See also Easily Fusible Alloys under Alloys.
The name amalgam is given to alloys of metals containing mercury. The
term comes to us from the alchemists. It signifies softening, because
an excess of mercury dissolves a large number of metals.
«Preparation of Amalgams.»—Mercury forms amalgams with most metals.
It unites directly and readily, either cold or hot, with potassium,
sodium, barium, strontium, calcium, magnesium, zinc, cadmium, tin,
antimony, lead, bismuth, silver, and gold; directly, but more
difficultly, with aluminum, copper, and palladium. This combination
takes place oftenest at the ordinary temperature; certain metals,
however, like aluminum and antimony, combine only when heated in
presence of quicksilver.
Quicksilver has no direct action on metals of high fusing points:
manganese, iron, nickel, cobalt, uranium, platinum, and their
congeners. Still, amalgams of these metals can be obtained of butyrous
consistency, either by electrolysis of their saline solutions,
employing quicksilver as the negative electrode, or by the action
of an alkaline amalgam (potassium or sodium), on their concentrated
and neutral saline solutions. These same refractory metals are also
amalgamated superficially when immersed in the amalgam of sodium or of
ammonium in presence of water.