Let me share what I just recently experienced. The instructor did a bisque at cone 010 (found out later it could have been 012) because her other class was going to do a saggar firing. So-o-o-o-o, I placed 23 tiles (3x3), 2 trays and 2 vases to be bisqued --I was NOT going to do a saggar firing. Clay=112 (with specks) Then, I glazed the 2 vases with clear and glazed the upper 1 inch with red and the 2 trays with clear also. Well, they all came out looking as if I glazed them with puke (yellowish, tan) and the red was very spotchy. I have had great success with clear over 112. At the time, I wondered why my glaze experienced classmate didn't put any of hers in there. Now I know. I was going to experiment with my own underglazes on the tiles and hang them on copper wiring and attach them on a real cool rod. But, my 'testing' is going to be all for nothing because it won't be a true outcome since they weren't fired high enough ( they are red clay). Maybe I could re-fire them at 05 and then continue? I am going to attempt to include photos.