Heating Lacquer

Lacquer formulas designed for a hot application offer particular advantages. You can also heat ordinary lacquer, but the results could be a mixed bag. August 22, 2013

Question (WOODWEB Member) :
What are the pros and cons of heating lacquer when spraying? One pro I would assume is the cost saving of the reducer. On the other hand, people have told me that heating lacquer makes it brittle. I'm using a Kremlin. What's the real story?

Forum Responses
(Finishing Forum)
From contributor C:
Solvent lacquers can be heated. If water-based, I will leave that to others.

Hot lacquers were used extensively up to the late 70's by most manufacturers, but were formulated differently than cold lacquers - they were higher solids, usually around 40-45%, some more. The solvent blend was also different, giving the lacquer extended open time. It would go on kind of pebbly but lay out like glass in a short time. This cut down on sanding and rubbing out later on.

You can warm cold lacquer, but any time you have more than 10 degrees difference between the lac temp and the substrate temp, it can be problematic. I once had a top actually crack instantly because of this. With hydro lacs, this is less of a problem since the water evaporates slower, but I would still be cautious of higher temp differences than 10 or so. It is being used with good success in California, so I know it works, just don't use aqueous emulsion finishes unless I have to.

The air/substrate/warm lac all need to be in the same range of temps for best result. Also there should be a heater both at the source of finish (pot/pump/cup) and at the booth, with an insulated or heated hose for solvent types. Won't hurt to have this for aqueous either.

From contributor R:
Isn't it better to raise the ambient temperature of the shop/spray booth and let the material, work piece and spray equipment get to the desired temp rather than heating each component individually? Although heating the material (lacquer) in a water bath might be faster, it just seems easier to plan ahead.

From contributor R:
Contributor C responded "of course in the factories they had forced air make up heat, so that everything stayed warm, and with true hot lacquer, it was applied at high temps (140 degrees) so you didn't need to adjust the temps to that point, just regular 75 degree. With cold lacquer, it's different - at that temp it would cause air bubbles to form because the wood would be heated too much and too quickly. It's not that it's a bad way, just not as efficient as a true hot lacquer would be."

From contributor B:
During the winter I warm my lacquer (SW solvent product) to where the bucket just feels warm. Sure improves the spray quality (Kremlin). I am using a belt heater from Granger which is easier than putting the can in a sink of hot water. Is it right? I don't know, but it works.