796 NEW YORK STATE MUSEUM 



Comparative compositions of porcelain and white earthenware 



Japanese Wegeli porce- Belgian 



porcelain lain mix- white earth- 

 mixture ture enware mixture 



Per cent Per cent Per cent 



Clay substance 49 . 44 81.37 58.56 



Quartz... 45.36 5.53 30.36 



Feldspar 5.20 13.10 11.08 



Total 100 . 00 100 . 00 100 . 00 



The conclusions are that the difference between porcelain and 

 white earthenware depends on the temperature at which the mate- 

 rial is burned, viz, to vitrification or incipient sintering, and not 

 on the composition. 



Some porcelains are vitrified at a temperature of only 2400° F. 

 (Seger's cone 9). Examples of this are Soger's porcelain and 

 Copenhagen biscuit ware, whose rational compositions are as 

 follows : 



Compositions of Seger's porcelain and of Copenhagen biscuit ware 



vitrifying at 2400° F. 



Seger Copenhagen 



Per cent Per cent 



Clay substance 25 32 



Quartz 45 



Feldspar 30 68 



These bodies when burned show a glassy, conchoidal fracture. 

 As the feldspar is that part of the porcelain which brings about 

 the vitrification, we must assume from the Japanese and Wegeli 

 porcelain mixtures, given above, that a much higher temperature 

 is required to sinter them than the Soger and Copenhagen mixtures. 



It is possible to find mixtures showing all grades of transition 

 in composition between white earthenware and porcelain. 



As to the behavior of easily fusible white earthenware glazes 

 and porcelain glazes on these transitional members, ITecht finds 



