Extra heat breaks down resins and some curing agents, turning light colors yellow, and nitrogen oxides from direct gas-fired burners make it worse, a fault often called gas yellowing. Epoxies and hybrids yellow more readily than polyesters. A yellowed batch usually cannot be recovered except by recoating with an overbake-resistant powder.
Whites are yellowing on the top rail, that's right in front of the burner box, check the oven fumes.
If whites yellow only at one oven zone, check burner tuning and exhaust balance before changing powder.
Also heard as
- gas yellowing
- overbake yellowing
Related terms
Overbake
Cure that went too hot or too long, causing yellowing, gloss loss and brittle film.
Cook
Line slang for curing parts in the oven, and in the past tense, for parts that got too much heat.
Bloom
A hazy, greasy film that forms on cured powder, often wiping off with a cloth.
Delta E
A single number for how far a color is from its standard, read by a spectrophotometer.