Slip or Loam Glazes Glazes made from natural clay slip began to be used by North American stoneware potters in the early nineteenth century and are the second most common glaze on North American utilitarian stoneware (Greer 1981:194, 197).
Originally created from alluvial clays mined from New York State, the term has come to refer to any dark brown or black firing slip clay (Greer 1981:265). Use of Albany slip began in the first quarter of the nineteenth century around the Albany area, but use was widespread by mid-century (Guilland 1971:85; Greer 1981:194).
Generally chocolate brown from the high iron content of the clay, the color of Albany slip could vary from to black to reddish brown and even olive green, based on various firing factors, such as an oxidizing atmosphere in the kiln, or yellowish bleaching caused by deposits of fly ash during a wood firing (Greer 1981:38).
After around 1920, Bristol glaze was most often used alone, and sometimes embellished with sponging, stamping, decals or sprayed colors (Greer 1981:212). If applied over a stoneware body that has a high iron content, Bristol glaze will sometimes have a pinkish cast.