Page 493

 
Slip casting: Forming an object by casting slip 
   into a porous mold, usually made of plaster. 
   Slip-casting clays must remain in suspen- 
   sion but should not contain enough water 
   to saturate the mold too deeply. 
Slip trailing: Ornament created by applying 
   slip (see above) through a vessel mounted 
   with one or more nozzles. 
Slipware: Earthenware decorated with slip (see 
   above) of a contrasting color. 
Stoneware: A ceramic body that is dense, fairly 
   highly vitrified, nonporous, and typically 
   fired at temperatures in excess of 1100' C. 
   Depending on the added colorants, the body 
   can range firom pale buff to a variety of col- 
   ors or black. 
Throwing: A process used for tbrning a pot 
    on the potter's wheel. Throwing clays differ 
    in "tooth" from those used for casting and 
    must not be so plastic that they collapse 
    after shaping. 
Tin glaze: Lead glaze made an opaque white 
    by adding tin oxide. Tin glaze was used to 
    imitate the appearance of porcelain on 
    earthenwares known as delftware, faience, 
    and maiolica (see above). 
 Turning: The creation of usually horizontal 
    banding by rotating a leather-hard (mostly 
    dried), unfired clay body on a lathe or a 
    wheel and carving it with a sharp tool. 
 Underglaze or in glaze decoration: Colored 
    ornament applied to an unfired or once- 
    fired (biscuit) clay body before firing the 
    glaze. 
 Vitrification: The process of raising the tem- 
    perature of most clays above about 800t C., 
    causing the body to begin to melt or fuse. 
    When cooled, the melted material becomes 
    glasslike, or vitrtfied. The high iron oxide 
    content of common red clays causes them 
    to begin to vitrily at lower temperatures; 
    comparatively iron-flee clays such as those 
    used fbr porcelain have a much higher vitri- 
    ficatioi point. Vitrification bonds the body 
    together and makes it less porous. Earthen- 
    ware is least highly vitrified and remains 
    porous. Stoneware is highly vitrified and 
    impervious to flutis. Porcelain is the most 
    vitrified: its typically low iron content pro- 
    duces the ware's characteristic white, 
    translucent body. 
 Waster: U sually a ceramic that was damaged 
     in or did not survive the firing process. 
     Wasters commonly are fbund at pottery- 
     making sites and are used as aids in identi- 
     lying intact pottery friom the lactories at 
     those sites. 
The Longridge Collection 493