218,127. Ohlsen, J. U. Ahlmann-. July 25, 1923. Pottery; making and waterproofing bricks.- Tubes, bricks, and other articles are made by moulding a mixture of diatomaceous earth, clay, and a low-fusing flux such as alkali silicate, then baking, and finally impregnating with melted asphalt, tar, pitch, bitumen, or paraffin. The plastic articles are: preferably moulded at a high pressure, for example 100 to 300 atmospheres. The impregnation may be effected in open or closed vessels; in the latter case, the articles may be first subjected to a vacuum and be impregnated under pressure. In one example, 5 parts of dried and ground diatomaceous earth, 1 part of clay, and 1 part of flux, such as mineral meal, are moulded wet ; the articles are then dried and burned at a temperature of 1400‹ to 1800‹ F., and while still hot are dipped into or otherwise impregnated with asphalt or like material. In another example, the articles are moulded from a mixture of 10 parts of raw dried diatomaceous earth, 5 parts of burnt diatomaceous earth, 4 parts of clay, and 1 part of alkali silicate. The products are acid proof and impermeable to air and fluids.
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