Alberta Slip with 20% added frit 3134 (left) fired to cone 6 on a porcelain. This is the standard GA6-A recipe. On the right 20% frit 3249 has been used instead. That is a low expansion frit so if you have crazing with the standard recipe, consider trying this one.
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.