Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2002

Baking (stoving) Paints in an Oven - Preventing Solvent and Moisture Blisters

Q. We apply a protective poly film onto the surfaces of panels, doors and chasses. Is there an additional air flash-off time required to prevent solvent blisters or moisture traps under the poly film ??

A. When you cure or bake a liquid coating it is always good practice to have a flash off zone or an entrance vestibule into the oven that is not as hot as the temperature inside the oven itself. To prevent solvent or water blisters (in the case of waterborne coatings), you do not want the temperature to be too hot or the solvents/water will boil under the paint film. After the coating has passed through the flash off zone or medium temperature section of the oven and the solvents or water have essentially evaporated, you can then allow the painted parts to enter the high temperature section of the oven where full curing will take place. Once the coating has been cured you no longer need a flash of area, but you allow time for the parts to cool to room temperature.

I can't answer the question as it relates to powder coatings.