Color Cement Handicraft

by Pedro J. Lemos; Reta A. Lemos

TO MIX PLASTER SUCCESSFULLY for molds observe the following directions: A bucket or pan large enough to contain the required amount of plaster needed should be used. Then half the water for the amount of plaster used should be poured into the bucket. Sift the plaster-of-Paris through the fingers into the water, until the water absorbs it no longer. This can be determined by small portions of the plaster remaining on the surface. Then stir the whole mass slowly with the mixing paddle until the passage of the paddle through the plaster leaves a channel which closes up slowly.

IT IS THEN POURED PROMPTLY into the center of the space on the glass prepared for the plaster tile so that the poured plaster gradually spreads from the center toward the corners and edges filling up the spaces and coming up the sides to about one-half inch height. Jarring the table or a slight shaking of the glass will cause the plaster to settle very level as well as causing any bubbles in the plaster to rise to the surface and break. Care should be taken that the plaster is not too thick before being poured. This stage of the proceedings requires one having their wits alert, and discussing Futurist art or any other topic may result in “try, try again.” If the plaster appears too thin more plaster should be added until it is the proper consistency.

After the plaster is poured it should set for about half an hour (varying according to the dryness of the atmosphere) before any attempt is made to remove it. Meanwhile all buckets, paddles, ladles, etc., containing plaster should be cleaned while the plaster is soft and easy to remove.

WHEN THE PLASTER MOLD IS READY TO REMOVE, a table knife slightly inserted between partitions and carefully pryed will cause the parts to separate. A most important part of casting molds and the using of the plaster molds is the oiling. All parts of the molds to come in contact with fresh plaster, cement or concrete must be thoroughly oiled or greased to prevent them sticking to each other. If wood, glass or metal is used with plaster, cement or concrete, remember to oil or grease such surface before pouring the plaster or cement on it. If you do not, you will have to use a chisel and with discouraging results.

The best way to oil the surface is as follows:

GLASS—Apply salad oil with brush or cloth removing as much as will come with the palm of the hand.

PLASTER BARS AND MOLD should first be soaked in water ten or fifteen minutes to prevent drawing the moisture out of the fresh plaster or cement. Wipe off surface moisture with soft cloth, and replace with oil, before using for molding. If oil is left thick or in brush streaks, it will leave its influence on the surface of the casting.

WOOD—A smooth-surfaced wood should always be used, and oiled well.

A good grease formula for all surfaces is as follows: Three parts paraffin and one part tallow, melt and add one pint of kerosene. This is applied with a brush.

AS AN EXPERIMENT PROBLEM for the use of plaster so as to become familiar with its use, we will proceed with the casting of a simple flat plaster tile.