Fired pottery color

The simplest and coarsest type of pottery is a lightweight, very porous, and typically red-colored terracotta that is fired at temperatures below 850°C. Much of ancient pottery, for example, is of the terracotta type. Excavations in the Near East have revealed that primitive terracotta vessels were being made there more than 8000 years ago characteristic types of terracotta were developed in China by about 5000 b.c. 

Uses. Constituent of alloys with other metals (tin, lead, copper) sulfides used in compounding of rubber and manufacture of pyrotechnics trioxide used as a fire retardant in plastics, rubbers, textiles, and paints chlorides used as coloring agents and as catalysts fluorides used in organic synthesis and pottery manufacmre... 

Dumas remarks that the choice of the crucibles is very important, and that the Hessian ones are better than those of porcelain. The crucibles sometimes color the metal yellow or brown, when particles of iron are detached from the internal surface. TMb inconvenience is not to be apprehended with crucibles of hard porcelain, but these often break or run out, and are too permeable, A pottery or porcelain furnace is used to melt the material, and the crucibles remain in the fire about twenty-four hours. The more tranquil and prolonged the fusion, the greater hardness and beauty does the strass acquire. If the crucibles are of excellent quality, a porcelain furnace maybe used but when the loss occurring is too great, one must be contented with a common potter s furnace. 

Fruiri Which it appears that the plastic efay trader experiment contained in its natural state tot admixture of some substance that diminished its power1 of contraction, and which was removed from it by decantation in water, increasing the contractile power, In the potteries a very important practice is adopted, that of combining together the several kinds of clay found to produce the best result in the fire, hoth as regards the contraction, color, and refractory nstore of the mate. 

---