Color Cement Handicraft

by Pedro J. Lemos; Reta A. Lemos

TO INCISE THE PATTERN take a nail point or nut pick or other metal point and shape the point on a grindstone or by the use of a file so that each incised line will have a tapering side. If any undercuts are produced the cast or plaster that is poured into it will become locked and refuse to separate.

The tile is next immersed in water, taken out and after the water is absorbed, a brushing of oil is given to it.

A PLASTER TILE IS MADE MORE DURABLE if it is dried and given a coat or two of shellac before it is used for molding plaster or cement. Otherwise repeated brushing of damp plaster with the oil brush will gradually wear the edges and details of the mold away.

TO MAKE A CAST FROM THE PLASTER MOLD, it is surrounded with the retaining bars after they have been oiled and held in position with the modeling wax or clay; this time they are placed firmly against the sides of the plaster mold.

THE CAST OF OUR FIRST EXPERIMENT now becomes the mold for our second practice problem as the mold is always the part that produces the cast. The cast in turn may become a mold for another cast.

TO SEPARATE THE CAST FROM THE MOLD the bars are removed and a knife edge is pressed between the parts to separate them. Care should be taken not to become too anxious and force the sections apart before the cast has dried or they will cause it to break. If it refuses to come apart easily when completely dry, a little wooden wedge tapped into the crevices in one or two places will cause it to part easily. Sometimes plaster flows over the sides of the mold and binds the edges together. On removing the mold and cast from the retaining bars, examine it to see if any plaster is binding it and if so remove it.

IF THE PARTS ARE ABSOLUTELY SOLID it is because the incising was not properly done and the lines interlock somewhere and the only thing to do is to break them apart and correct the faults and try again. Sometimes when interlocking tiles are separated the faulty parts have fragments of the opposite part attached in the defective parts showing where the faults are located.

THE TWO PLASTER TILES SHOULD BE RETAINED for they can be used in casting plain cement and color cement tiles in various finishes. When they have completely dried they should be given two or three coats of thin shellac, a day apart, on the surface only, which will make them good durable molds for future use.

CASTING IN THE ROUND is more difficult than flat casting or bas-relief work and while the making of plaster molds for vases and bowls is given particular attention in the chapter on Cement Bowls and Vases, directions for casting objects in the round will be given here.

AS A GOOD TEST PROBLEM take any small object or toy and, if it is wood, oil it well. If it is porcelain or glass it will not need to be oiled. A simple form, animal or bird, can be made in modeling wax or clay to be used as the original or model from which to make a mold. The best objects are those modeled in broad surfaces with but little detail.