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?
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.