Both of these Zero4 fritware porcelain mugs were bisque fired at 1450F and glaze fired at cone 04. The Grolleg version of the porcelain is burning a much pinker color (both the bare body and under our G1916Q3 glaze). In typical feldspar porcelains the color difference between these two kaolins is not nearly so much but here the extra glass development is likely amplifying the presence of even just a little more iron oxide.
New Zealand Halloysite
The whitest burning kaolin we have ever seen. It is very sticky when wet, suspends glazes well & makes super white porcelain (with help from a white bentonite).
A white burning kaolin from the UK, commonly used in porcelain bodies and as a glaze suspender. Sticky when wet, low plasticity.
The designation for a group recipes for body, glaze and engobe (by Tony Hansen), that potters can use to make low fire stoneware and fritware porcelain