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Leather, Ink, and Miscellaneous: Paris

Gypsum is also used as a fertilizer, and in the manufacture of glass and porcelain. Plaster of Paris is chiefly used for making models and casts, and as a cement for marble and alabaster.

Among the most celebrated gypsum beds in the world are those of Montin the world are those of Montmartre near Paris, which have given plaster of Paris its name.

Alabaster.

This is a variety of gypsum of great beauty and easily carved on account of its softness; hence it is extensively employed for ornamental purposes.

To Use Plaster of Paris. - To use plaster of Paris, mix it with water to the consistency of thick cream and apply at once, as it sets quickly. No more should be mixed at a time than will be required for immediate use.

Or, if additional strength is desired, mix with a thin glue size, or a solution of 1 or 2 ounces of gum arabic in 1 pint of water. These not only harden the plaster but give its surface face a desirable smoothness.

Or mix plaster of Paris with an equal weight of sulphate of potassium, and thin with 2 to 6 parts of ly and is harder than plaster of Paris water. This mixture sets very quickalone.

Setting. - To Prevent Plaster of Paris from Mix 2 per cent of alum, sulphate of potash, or borax, with plaster of Paris before adding water, and it will be prevented from solidifying for 3 or 4 hours. Thus it can be handled much more readily. When dry, it will also be much harder than plaster of Paris alone. - Or mix with vinegar diluted with longer the plaster will require to set. water. The more vinegar used the used the Molds for Plaster of Paris.

To make molds for casting plaster ornaments, mix 12 ounces of rosin, 8 ounces of tallow, and 6 ounces of beeswax.

Or use plaster of Paris itself.

Or mix equal quantities of clean white sand and pulverized limestone or marble dust, and to 14 pounds of this mixture add 1 pound of litharge and 4 pounds of linseed oil. Grind or rub up the litharge with the oil, heat the mixture of sand and limestone to dryness, stir into a stiff mortar, and pour in an oiled mold. To Cast Plaster of Paris. - Oil the object to be copied and cover it to a mixtures, so that when removed the sufficient depth with one of the above mold will be strong enough to handle. If plaster of Paris is used to make the mold, the object to be copmust be moistened, but no drops must be allowed to stand on the surface.

The mold should be made in two parts, which may be done by molding LEATHER, INK, AND MISCELLANEOUS first one side up to a given line, and then the other. Leave an opening through which to pour the plaster.

To make castings, it is only necessary to oil or moisten the inside of a mold. Lock the two parts of the mold together, oil the edges so that they can be readily separated, and pour the mold full of plaster from a funnel through the opening left for that purpose. After the plaster has set, the mold may be removed and used repeatedly.

To Harden Plaster-of-Paris Objects. Put in an iron kettle 2 pounds of a solution of caustic potash. Add in shavings 2 ounces of stearin and 2 ounces of castile soap, and boil for half an hour, stirring constantly. Add 1 ounce of pearlash dissolved in a little soft water. Let the whole boil up, remove from the fire, and stir until cold. Now stir in cold potash lye until the mass becomes perfectly liquid and falls in drops from the stirrer. Let stand for several days tightly covered before using. This preparation will keep for years.

Clean the plaster-of-Paris casts and other objects free from dust and stains, and apply this mixture with a paint brush as long as the plaster of Paris will absorb it. Let dry and dust with a brush or chamois leather.

Repeat, if necessary, until the casts take on a satisfactory polish. - To Make Artificial Marble. Mix plaster of Paris with a solution of alum, put it in an oven, and bake until the water is completely evaporated. Afterwards grind to powder. Mix with water and stir in any desired coloring matter in powdered form to make clouds and veins. When dry, this mixture sets very hard and takes a high polish.

To Imitate Alabaster. To imitate alabaster with objects made of plaster of Paris, warm the articles and suspend them by means of horsehair or fine wire in melted white wax of the best quality. Continue until the plaster of Paris has absorbed all it can. Hang up the articles to dry, and polish with a clean brush. Any pure white wax will answer this purpose.

To harden these objects, suspend them in a clear solution of alum until crystals form upon the surface. Remove, and polish with a damp cloth.

To Clean Alabaster. - Wash with castile soap and water.

Or, to remove stains, cover with white fuller's earth or pipe clay. Let stand for a few hours and wash off.

Or, if much stained, wash with very dilute sulphuric acid, using about 1 ounce of sulphuric acid to 20 ounces of water.

Or rub with a cloth moistened with lemon juice and dipped in pumice stone. Rinse with clear water and polish with a dry chamois.

To Make Prepared Chalk.-Add a solution of carbonate of soda to a solution of muriate of lime as long as the chalk is precipitated. Strain through filter paper and then pour on clear water until the sediment is perfectly clean. Dry in direct sunshine.

Safety Matches. - To make safety matches, mix 6 ounces of chloride of potash, 2 ounces of bichromate of potash, 2 ounces of ferric oxide with 3 ounces of strong liquid glue. Mix thoroughly with gentle heat, taking care that it does not take fire, and dip the match heads in this. These matches will not kindle on sandpaper or by ordinary friction, but must be rubbed on a surface especially prepared for them as follows: Mix 10 ounces of sulphide of antimony, 2 ounces of bichromate of potash, 2 ounces of oxide of iron, lead, or manganese, 1 ounce of glass powder, 2 ounces of strong glue or gum. This preparation is spread like paint while warm on suitable paper, which is fastened on the boxes containing the matches.

Or dissolve 4 ounces of gum arabic in just enough water to make thick mucilage or paste, and stir in 4 ounces of powdered peroxide of manganese, 2½ ounces of phosphorus, and place on the back of a closed stove, but do not heat above 130° F. or expose to an open flame. Stir until the phosphorus is melted, then add 34 ounces of niter and stir the whole to a uniform paste. First dip the matches in melted brimstone, let dry, and afterwards dip the heads in this substance. This mixture may be perfumed by the addition of ounce of gum benzoin. The lids of the boxes may be coated with the same mixture by means of a brush, or pieces of sandpaper may be coated in the same manner, and attached to match safes or boxes for convenience in lighting.

Ordinary Matches. Dip the matches first in hot melted sulphur, let dry and steep in turpentine. Afterwards dip the heads in a mixture of 5 ounces of chloride of potash, 5 ounces of flowers of sulphur, 1 ounce of vermilion mixed to a paste with oil of turpentine.

Or dip the matches in hot melted sulphur, steep in turpentine, and dip the heads in a mixture of 4 ounces of melted glue, 1 ounce of phosphorus with the addition of whiting stirred in to make it of the right consistency, and vermilion, or lampblack to color.