Bulletin . AUO, SiO, Feldspar = = 55-2CaCOg = Crazing is comparatively rare in this type of porcelain glaze,due to the vitreous nature of the body and the similarity in compo-sition of body and glaze. In order to intensify crazing and tolocate that portion of the field in which it would be most likely tooccur, the glazes w^ere applied to porous, biscuit wall tile, whichshrunk considerably but were still porous at the end of the bum. The glazes were applied a little thicker than is customaryin practice, and the trials set in tile saggers and burned to coneII in 36 hour
Bulletin . AUO, SiO, Feldspar = = 55-2CaCOg = Crazing is comparatively rare in this type of porcelain glaze,due to the vitreous nature of the body and the similarity in compo-sition of body and glaze. In order to intensify crazing and tolocate that portion of the field in which it would be most likely tooccur, the glazes w^ere applied to porous, biscuit wall tile, whichshrunk considerably but were still porous at the end of the bum. The glazes were applied a little thicker than is customaryin practice, and the trials set in tile saggers and burned to coneII in 36 hours. The results are shown graphically in ChartsI and II. DISCUSSION OF RESULTS. On Chart i, the molecular variations of silica are plottedalong the abscissa and the molecular variations of alumina along INFLUENCES OF SILICA AND ALUMINA ON PORCELAIN GLAZES. 19 the ordinate. The letters at the left denote the horizontal series TRANS. AM. CER. SOC. VOL. XIV CHART i STULL yr. /.2 /S £.^ ^.2 S.^ and the numbers along the top the vertical series, so that eachglaze is located by a letter and a number. KpiSince the RO for all glazes is constant, j i the formula CaoJof any glaze can be read from the chart by referring to the ordi-nate for its alumina and to the abscissa for the silica. For K,Oiexample, the formula of E-5 is | ^ AUOg Si02. [ CaOJThe alumina is constant in a horizontal series while the silicavaries. In a vertical series the silica is constant and the aluminais the variable. To the left of the line M J are the underfired mattes, and 20 INFLUENCES OF SILICA AND ALUMINA ON PORCELAIN GLAZES. between M J and N U are the matured mattes. BetweenN U and N K are mattes showing a sheea or sHght gloss anddesignated as semi-mattes. The bright glazes occur betweenN K and O S, and below O S the glazes are devitrifled. Theglazes are all crazes below the line I P R L and all sound abovethis line. The d
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherurbana, bookyear190
