Or, instead of gold leaf, apply bronze powder, and when dry coat with copal varnish.
Or, to retouch gilt frames, apply isinglass size to chipped or broken places, and when it becomes tacky lay on gold leaf gently with a pad of cotton wool, and when dry burnish.
Or retouch with gold paint by means of a camel's-hair brush.
Silver.—Silver is the whitest of the metals capable of taking a brilliant polish. It is malleable and ductile. The finest silver leaf requires 1,000, 000 sheets to make an inch in thick ness. A grain of silver may be drawn into a wire 400 feet in length. Silver is ten or eleven times as heavy as water, according to condition and purity. Melted silver absorbs from the air about twenty times its volume of oxygen, which is given off when the metal solidifies. As the surface tends to cool first, the ejection of this oxy gen from the inner part of the mass may cause an explosion. Hence it is customary to melt silver under pow dered charcoal or in the presence of niter. Silver conducts heat and elec tricity, and can be welded and alloyed with gold, copper, and other metals. In addition to its use in coinage, which is very ancient, silver is largely used for tableware and jewelry, but solid silver is now replaced largely by alloys of nickel and other metals, which are covered with pure silver by elec troplating. Silver coin contains a pro portion of alloy, usually copper. The United States and French standard of fineness is 900, or 900 parts of silver to 100 of copper. In Great Britain the standard is .99.5. This is the fine ness of sterling silverware.
Among the compounds of silver, sil ver chloride is used in photography, and silver nitrate, or lunar caustic, is used in surgery, photography, elec troplating, and for marking inks.
Silver Jewelry. — Common jewelry contains a portion of alloy, according to the degree of hardness required. Sterling silver contains 9l5 parts sil ver, 75 parts copper. The hardest al loy contains 4 silver, 1 copper. A medium hard alloy, 3 sterling silver, 1 brass wire. A soft alloy, 2 pure silver, I brass wire.
Silver Solder.—Silver 19, copper 1, brass 10.
Or silver 2, brass 1 with borax.
Or silver 4, brass 3, zinc 1 r with borax.
For silver plate, silver 2, brass 1 with borax.
To Purify Silver.—To obtain pure silver, dissolve silver containing alloy in nitric acid, and add a solution of common salt as long as a precipitate is formed. Boil the sediment in water in a bright iron vessel, wash with clean water, and dry.
Silver Tree. — Dissolve 1 ounce of nitrate of silver in 35 ounces of dis tilled water. Filter and put the liquid in a suitable glass vessel where it will not be disturbed. Pour in 1 ounce of ,mercury. A beautiful silver tree will form.
United States Mint Test for Coun terfeit Silver.—Dissolve 24 grains of nitrate of silver in 30 drops of nitric acid and 1 ounce of water. Scrape the coin to be tested and apply a drop of the liquid. If it turns black, reject it.
To Clean Silver. — To clean orna ments of jewelry and silver, put the articles in suds made of castile soap in hot water and bring to a boil. Re move from the fire and let the articles stand in the suds until they will bear the hands, then scrub gently with a soft toothbrush or jeweler's brush, rinse in clear water, dip in benzine or alcohol, place in an earthenware bowl or other utensil, and cover with box wood shavings. Let this stand in a warm place until the articles are per fectly dry. Any moisture remaining on them causes them to tarnish. When not in use they should be put in a wooden box and covered with fine sawdust.
Silvering.—A thin coating of me tallic silver may be added to other metals, glass, textile fabrics, and other materials, either in various mixtures in liquid form or by means of silver powder or silver leaf.
For a silver solution without elec tricity, dissolve nitrate of silver in soft water, using 1 ounce of silver to 1 quart of water. Add slowly hy posulphite of soda in crystals, stir ring the mixture with a glass rod. A brown precipitate will form, but if additional hyposulphite is added, it will again dissolve. A little more hy posulphite should then be added. The articles to be silvered may be dipped in this solution, or it may be applied to them with a brush or sponge.