To repair cracked church-bells so that their tone will be as good as new, put a furnace in the middle of the bell so as to heat same, and after fusion of the edges of the crack, pour new bell-metal in same. The wall of the bell must be blocked up in order to prevent the escape of liquid metal.
To clean bronze: Take 1 ounce of oxalic acid, 6 ounces rottenstone, 1 or 2 ounces gum arabic in powder, 10 ounces sweet oil, and a sufficient quantity of water to make a paste. Apply a small portion to the pan, and polish with a flannel or piece of soft leather.
Boil them in ordinary soap boilers' lye, rinse with water and roll in sawdust or bran. When the bronze is pressed mix the lye with common salt and brush the article thoroughly, allowing no water to touch the back.
To clean chandeliers or gas fixtures they should be taken apart and the separate parts boiled for a few minutes in a sharp lye, followed by their cleansing with a soft brush. They should next be drawn through a strong solution of potassium cyanide, then washed in a large boiler with hot water, dried in clean sawdust and then polished with chamois skin. In some cases parts should be lacquered after they have been put together again.
To clean coins and medals a mildly concentrated solution of potassium cyanide is recommended. When medals or other small silver objects are to be cleaned, three vessels or glasses should be placed side by side, two of which are filled with water and the third with a solution of potassium cyanide. The object to be cleaned is to be taken up with brass tweezers and dipped in the vessel containing the potassium cyanide. This will cause the brown or dirty yellow coating on same to vanish at once. The medals, or other objects, are then to be rapidly rinsed in the second and third tumblers, and then dried with a linen cloth. Articles of a larger size, such as spoons, candlesticks, chafing-dishes, etc., are treated by wetting the yellow places with a small tuft of cotton thoroughly moistened with a solution of potassium cyanide, then washed and dried. The modus operandi is the same for gilded articles.
To cleanse bronze by oil, tallow, fat or other grease, boil it in an infusion of ashes and clean with a soft brush dipped in a fluid consisting of equal parts of nitric acid, alum and water. Dry each piece with a rag, and heat slightly. When it is desired to clean clock pendulums and free them from what is technically known as "mercury dust," they should be heated slightly and the stain touched with a brush dipped in nitric acid. Then rub with a linen rag and heat moderately a second time.
To clean marble mix 2 parts of common soda, 1 part powdered pumice stone and 1 part powdered chalk with water. Rub it well over the marble and then wash the marble with soap and water.
To clean articles of antique brass, such as sword-hilts, mountings, etc., dip them in a compound of 1/2 part sulphuric acid and 1 part nitric acid. After a brief immersion take them out, rinse thoroughly in cold water, dry in sawdust and then polish with finely pulverized Vienna lime.