The following chapters by no means complete the story of color cement. They record the results of the work of the authors and it is hoped that it will stimulate interested readers to carry this delightful handicraft to even greater achievements.
The results achieved have been accomplished through several years’ patient experimenting by the authors, but the realization that many other teachers, craftsmen and students will be aided in continuing this delightful, durable handicraft, is in itself an enjoyable reward to the authors for their efforts.
Reta A. Lemos
Pedro J. Lemos
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| CHAPTER 1 Materials and Equipment | ||
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IN THE MAKING OF COLOR CEMENT HANDICRAFT the chief material used is Portland cement. While this material has assumed a most important part in the building history of our present time, there are not many who know its history and source, and as every craftsman is a better craftsman if he knows something of the story of the material with which he works, here is the brief story of Portland cement.
PORTLAND CEMENT DERIVES ITS NAME because of resemblance in color to a stone quarried near Portland, England, and it was named by its inventor, Joseph Aspdin in 1824. It is a manufactured product produced by a scientific process. At the beginning of the Christian era the Romans used a natural cement very extensively, and many fragments of color frescoes and friezes remain from the work of the ancients, showing that they used color with their work.
THE PRINCIPAL INGREDIENTS OF PORTLAND CEMENT are lime, silica, iron, and alumina. These materials are mixed in definite proportions and then subjected to a degree of heat that almost causes them to melt, forming a clinker or slag. This clinker is ground until it is reduced to a powder, and this is the Portland cement. Portland cement is generally mixed with an aggregate to produce strength and this aggregate is usually stone, gravel or sand. The third material needed to complete the combination is water.