Glass & Pottery World Volume 11-12

Glass & Pottery World Volume 11-12

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 edition. Excerpt: ...He is told first that by increasing the percentage of silica in bodies, he increases his body coefficient, thereby reducing the liability to craze, and then further on he finds that leaving the body constant he may add silica to his glaze, thereby not increasing the glaze coefficient as might be supposed, but on the contrary reducing it. That is, the coefficient of the silica added to the body is greater than the average coefficient of the body ingredients. The final coefficient is therefore raised by adding it, while on the other hand the case is exactly reversed on adding it to a glaze. I called attention to this in my paper two years ago, and offered as an explanation the fact that while in the body the silica was non-combined, that is, free and crystalline, in the glaze it was combined and amorphous. Now, while the coefficient of the crystalline silica is high, that of the amorphous is very low; hence we have the increase in the body coefficient, and the decrease in the glaze. That crystalline silica has a high coefficient is well known. Probably the high expansion of a silica brick is the most striking proof. This coefficient has been accurately measured by Damour, who also measured the coefficient of various bodies, showing that one containing 75 per cent SiO had more than twice the expansion of one showing but 68.4 per cent. So the increase in the body coefficient is readily understood, but what striking proof have we of its low coefficient in glazes? This point was recalled to my mind on reading an article by Professor Witte, of Berlin, on what he calls an ideal glass. The article was really a discussion as to whether we should consider glass as a liquid or a solid, but the interest in connection with my subject lay in his...show more

Product details

  • Paperback
  • 189 x 246 x 18mm | 603g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236800605
  • 9781236800602