Tests on clay materials available in Illinois coal mines . ure. Summarizing the above remarks, we may list the following gen-eral requirements for the various wares : Paving-brick clays should have a fair plasticity, should not lam-inate seriously, should dry safely and oxidize easily. They should notvitrify too easily and should show a good heat range at low porosity. Front brick require clays of good molding and drying properties,easy of oxidation, of good color, and a fair range of burning tem-perature at which uniform colors can be obtained. 2Purdy, Ross C, Paving brick and paving brick cl
Tests on clay materials available in Illinois coal mines . ure. Summarizing the above remarks, we may list the following gen-eral requirements for the various wares : Paving-brick clays should have a fair plasticity, should not lam-inate seriously, should dry safely and oxidize easily. They should notvitrify too easily and should show a good heat range at low porosity. Front brick require clays of good molding and drying properties,easy of oxidation, of good color, and a fair range of burning tem-perature at which uniform colors can be obtained. 2Purdy, Ross C, Paving brick and paving brick clays of Illinois: 111. State GeoLSurvey Bull. 9, 1908. BEHAVIOR OF CLAYS DlRIXG BURNING 15 Common brick may be made from clays of fair plasticity andworking properties if the drying behavior is good, if they oxidize ina reasonable length of time and produce a hard sound ware withouttoo great danger of overburning. The manufacture of hollozc ware requires somewhat higher plas-ticity than would be necessary for brick, but other properties areabout the Fig. 2.—Briquets of a red shale (sample 50) and a bluff clay (sample 58)showing excessive surface pitting. [mportance of Long Heat RangeThe differences in temperature between the hottest and coolestparts of a kiln are influenced by the design of the kiln and the man-ner in which it is fired and controlled. The differences in temperaturewithin commercial kiln chambers have been found to vary from 20C to as high as 80° C, or from one to four cones. For this reasonit is essential that a clay should have a long heat range, so that warefrom different parts of the kiln may be uniform in color, size, anddensity. Lime, through its vigorous fluxing action when uniformly dis-tributed, imparts to clay a short heat range. The temperature intervalbetween vitrification and fusion is so short that it is dangerous toattempt the manufacture of a vitrified product from a calcareous , clays of this type may be valuable for the man
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcoalmin, bookyear1917
