I use terra sig on the bottoms of my majolica pieces (Highwater's low-fire Stans Red clay). I mix my own terra sig using Red Art. Have not had a problem with it until this past bisque firing and had one plate where the sig flaked off about the size of a quarter. The rest of the sig on that piece was fine.
I'm thinking of trying to put sig on the bare spot before glaze firing it. Has anyone ever used sig on bisque ware? And, any ideas on why it would have flaked off in the first place?