Part 48

«Bidery Metal.»—This is sometimes composed of 31 parts of zinc, 2 parts of copper, and 2 parts of lead; the whole is melted on a layer of rosin or wax to avoid oxidation. This metal is very resistive; it does not oxidize in air or moisture. It takes its name from the town of Bider, near Hyderabad (India), where it was prepared for the first time industrially for the manufacture of different utensils.

Other compositions of Indian Bidery metal (frequently imitated in England) are about as follows:

P.C. P.C. P.C. Copper 3.5 11.4 16 Zinc 93.4 84.3 112 Tin — 1.4 2 Lead 3.1 2.9 4

Erhardt recommends the following as being both ductile and hard:

Zinc 89 to 93 Tin 9 to 6 Lead 2 to 4 Copper 2 to 4

The tin is first melted, and the lead, zinc, and copper added successively.

«Zinc-Nickel.»—Zinc, 90 parts; nickel, 10 parts. Used in powder form for painting and cloth printing purposes.

«Platine for Dress Buttons.»—Copper, 43 parts; zinc, 57 parts.

«UNCLASSIFIED ALLOYS:»

«Alloys for Drawing Colors on Steel.»—Alloys of various composition are successfully used for drawing colors on steel. To draw to a straw color use 2 parts of lead and 1 part of tin, and melt in an iron ladle. Hold the steel piece to be drawn in the alloy as it melts and it will turn to straw color. This mixture melts at a temperature of about 437° F. For darker yellow use 9 parts of lead to 4 parts of tin, which melts at 458° F. For purple, use 3 parts of lead to 1 part of tin, the melting temperature being 482° F. For violet, use 9 parts of lead to 2 parts of tin, which melts at 494° F. Lead without any alloy will draw steel to a dark blue. The above apply to steel only since iron requires a somewhat greater heat and is more or less uncertain in handling.

«Alloy for Pattern Letters and Figures.»—A good alloy for casting 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