How can I improve 'toasting' in my fired clay body?

Toasting in the unglazed clay surface can be encouraged by having a thicker cross section of ware, slower drying and higher temperature firing. Salt deposits cause the toasted effect in clay bodies, often seen with Original Craft Crank 153-1114. The calcium combines with the iron content of the clay at higher temperatures. 

Toasting can also occur in iron-bearing bodies at glaze margins, or where glaze has been wiped back from the surface of the clay. In this scenario toasting is due to the flux residue from the glaze combining with the iron in the clay.