How To Use Cements

Take as small a quantity of the cement as possible, and bring the cement itself into intimate contact with the surfaces to be united. If glue is employed, the surface should be made so warm that the melted glue is not chilled before it has time to effect a thorough adhesion. Cements that are used in a fused state, as resin or shellac, will not adhere unless the parts to be joined are heated to the fusing point of the cement. Sealing-wax, or ordinary electrical cement, is a good agent for uniting metal to glass or stone, provided the masses to be united are made so hot as to fuse the cement, but if the cement is applied to them while they are cold it will not stick at all. This fact is well known to the itinerant vendors of cement for uniting earthenware. By heating two pieces of china or earthenware so that they will fuse shellac, they are able to smear them with a little of this gum, and join the pieces so that they will rather break at any other part than along the line of union.

But although people constantly see the operation performed, and buy liberally of the cement, it will be found in nine cases out of ten that the cement proves worthless in the hands of the purchasers, simply because they do not know how to use it. They are afraid to heat a delicate glass or porcelain vessel to a sufficient degree, or they are apt to use too much of the material, and the result is a failure.

Cement For Ivory Or Mother-Of-Pearl

Dissolve 1 part of isinglass and 2 of white glue in 30 parts of water, strain and evaporate to 6 parts, add one-thirtieth part of gum mastic, dissolved in one-half part of alcohol, add 1 part of white zinc. When required to use, warm and shake up.

Cement For Jet

Shellac is generally used for jet articles. The broken edges should be heated before applying the shellac. Should the joint be in sight, it will be rendered the same color as the jet itself by smoking the shellac before applying it.

Cheap India-Rubber Cement

Cut virgin or native India-rubber with a wet knife into the thinest possible slices, and with shears divide these into threads as fine as fine yarn. Put a small quantity of the shreds, (say one-tenth or less of the capacity of the bottle), into a wide-uiouthed bottle, and fill it three-quarters full with benzine of good quality perfectly free from oil. The rubber will swell up almost immediately, and in a few days, especially if often shaken, assume the consistency of honey. If it inclines to remain in undissolved masses, more benzine must be added, but if too thin and watery it needs more rubber. A piece of solid rubber the size of a walnut will make a pint of cement. It dries in a few minutes, and by using three coats in the usual manner, will unite leather straps, patches, rubber soles, backs of books, etc., with exceeding firmness.

Cement For Petroleum Lamps

Boil 3 parts of resin with 1 part of caustic soda and 5 of water. The composition is then mixed with half its weight of plaster-of-Paris, and sets firmly in one-half to three-fourths of an hour. It is of great adhesive power, not permeable to petroleum, a slow conductor of heat, and but superficially attacked by hot water.