File:Annual report of the Regents (1900) (14592246410).jpg

Identifier: annualreportof5421900newy (find matches)
Title: Annual report of the Regents
Year: 1889 (1880s)
Authors: New York State Museum University of the State of New York. Board of Regents
Subjects: New York State Museum Science
Publisher: Albany : J.B. Lyon, State Printer
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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rosity willbe diminished. The hardness of the material will also be increased,and this is specially true of calcareous clays. In the case of com-mon brick it is always the finest particles of the clay that softenwhen a temperature of about 1000° F. is reached, but the smallparticles of quartz sand do not soften, and therefore form the skele-ton of the mass, thus enabling the brick to hold its form. As at thistemperature the quartz sand expands as much as 16^, and conse-quently decreases in specific gravity, there will be a certain amountof decrease in the porosity from this cause. We therefore canobtain thoroughly dense brick from sandy clays, without the burn-ing process being accompanied by any material amount of shrink-age, the quartz having aided in rendering the clays more dense. In the burning the clay changes from a comparatively soft con-dition to one of rock-like hardness. The amount of heat appliedin burning and the temperature to which the kiln is raised depend fee aa o OS
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<=a m J2 OO a CLAYS OF NEW YORK 673 on the nature of the clay used and the grade of product desired.Common bricks for instance may not require a temperature of morethan 1800° F., while othe^ wares may have to be burned at a tem-perature of 2300° F. or 2500° F. In the burning process a number of different things exert moreor less influence and consequently must be taken into consideration.Among these we may mention the character of the clay, the char-acter of the fuel, the type of kiln to be used, the temperature em-ployed, the composition of the fire gases, etc. The detailed changes which the clay undergoes, when burnedhave already been mentioned. In burning, the wares are piled up in the kiln, as in the case ofcommon brick, and front brick, or they may have to be inclosedin receptacles to protect them from the action of fire gases, andthey may sometimes need to be partially inclo^d by means of firebrick slabs in order to prevent the exertion of any excessive pressureon them, wh

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