There are a few colors that do not react as well to the torch flame as they do the kiln.  A muddy grayish color appears when the torch flame is applied directly to whites, yellows, and pinks.  Applying a layer of flux underneath the color may reduce the effect; but, it will not eliminate the effect.

 

Colors containing cadmium respond differently to the torch flame as compared to kiln firing. 

 

I picked these tips up from Deb Lozier, one of the instructors,  at the Thompson Enamel Torch Firing Workshop held earlier this month.