CLAYS OF NEW YOEK 7Y5 



done any harm. The soluble salts may also get into the clay from 

 some of the materials used to color the tile artificially, nmber, for 

 example, being seldom free from sulfate of lime. 



Floor tile should be burned to a condition of great density, in 

 order that they may not absorb water, nor permit the entrance of 

 dirt into their pores, rendering their cleaning more difficult. 



Langenbeck (Chemistry of pottery, p. 156) gives the following 

 percentages of water absorbed by fioor tile of different colors. 



Water absorption of floor tile 



Color of the clay Extremes Averages 



Salmon .., 1.5—9.1 5.8 



Buff 1.9— Y.2 4.6 



Light gray 1.9—8.5 5.8 



Dark gray 2.0— 5.8 4.4 



Chocolate 0.0— 7.4 4.8 



Ked 1.5— 8.4 6.0 



Black 4.4—10.3 T.5 ' 



Eawn 8.3 



In the manufacture of encaustic tile, the clay that is to form the 

 surface of the tile and give the pattern is charged intO' the mold 

 first, while the clay that makes up the body is then put in on top 

 and the whole subjected to pressure in the machine. The molds 

 can be filled by machinery when the color of the tile is solid. 



With encaustic tile the molds have to be filled by hand. Where 

 the pattern is made up of clays of several different colors, a frame- 

 work of brass strips, so arranged as to mark the boundaries of each 

 color is first set into the mold, thus dividing it up into cells. Into 

 each of these the color is charged by means of a small hand scoop, 

 till every cell is filled with the color whose bouiLdaries it incloses. 

 The framework is then withdrawn from the mold, and the latter 

 filled up to the top with the clay that forms the body of the tile. 



It is essential that the clay forming the face and that which 

 serves as the backing should have the same expansion, otherwise 



