|Monthly Tech-Tip |
This is G2917 Ravenscrag floating blue and G2917A. The latter was also supposed to be floating blue. Both are descendants of the original G2826R floating blue, preserving its chemistry but sourcing it from more user-friendly materials. The glaze on the right takes the mechanisms of the other two and compromises the chemistry in the direction of lowering the thermal expansion (to reduce crazing). The use of high-MgO frit 3249 is part of the strategy (instead of sourcing it from talc or dolomite). But this has completely killed the visual! The solution will be to return to the use of talc to source the MgO.
A popular cone 6 glaze that employed Gerstley Borate, it was very troublesome to use and to fire. Much work has been done to create alternative recipes.
Ferro Frit 3249
A magnesia borosilicate frit having very low thermal expansion and melting point. Invaluable in pottery as to increase the MgO in glazes to prevent crazing.