Lower Temperature Limits for Spraying Finishes
How cold is too cold for wood finishing? March 12, 2009
Hello all. We have a small spray booth inside our building - no exterior walls but it has four walls. Our spray guy thinks we need to put heat in his booth and he feels it's too cold in his room. The average temperature is 50 degrees in the winter inside the booth. What's the coldest it can be to spray?
From contributor J:
The answer to your question will have everything to do with what you're spraying. The data sheets for the coating should give you the factory's opinion which will likely be an 'ideal' condition.
We spray MLC Magnamax and try to keep the temperature in the room above 60 degrees. The factory says the temp must be above 68 degrees for the material to cross-link the way it should. The regional sales rep disagrees. In any case, sometimes we just can't get there. We've sprayed between 55 and 60 several times and haven't had any finish problems (failures). Obviously the drying time is longer.
In the past, I've switched over to Target Coating's Ultima Spray Lacquer during colder times. This water base product is much less sensitive to cold. Also, no worries when we put heat in the paint room with our propane bullet heater. That could be disastrous with solvent based coatings. Great question! I've scratched my head (and prayed) many times about this subject. I look forward to the answers from others.
From contributor O:
I have to spray outside and have sprayed Behlen (Junk), ML Cambpell, and SW lacquer products below freezing. The only thing that was bothered by the cold was me.
Note: I try to only spray on dry sunny days. Also, the casework was also close to the ambient temp.
From contributor R:
I've been spraying Sherwin Williams Pre-Cat Lacquer for years and have been spraying below fifty degrees and sometimes closer to freezing during the winter a great many times. I would estimate I've probably shot 100 gallons in these temps. I never had a finish failure on a job I shot. I did once have a finish failure where we went from a dry climate (even in winter with the snow), to a wet climate (Seattle in the winter) where the wood swelled. Iíve also had sample doors that sit day after day, year after year out in the cold fail (shatter effect), but never on a job that is shot in the cold and then within a month installed in a temperature controlled house. I still sweat it every time, but when it's 0 degrees outside there is just no way I can get it up where they want it with the spray booth running.
For what it is worth, I was trained with CV and just assumed the spec's for SW pre-cat said the same thing about keeping it above 65 for crosslinking, but their sheets don't for the pre-cat. I even spoke to the head guy at the Seattle industrial supply SW headquarters and while he did not want to say it, he pretty much admitted it just slows the crosslinking way down.
From contributor M:
With CV you are headed for trouble. First thing is the viscosity will be much higher in the colder temp. The big thing though will not happen for six months to a year. The cold temperature will stop the catalyzation process and you can get the finish to shatter. I have seen this several times before. It is the same as if you apply more than the four mil dry film thickness. The sales rep never will tell you anything, just have a finish fail and talk to the testing lab. They are just chocked full of info all of a sudden. Pre-cat lacquers would depend on the formulation. The closer the chemistry is to CV the more likely they are to fail. I have seen Chemcrafts Opticlear fail due to cold checking.
From contributor S:
The coldest you can spray I would guess is as cold as it can get before the material starts freezing before it hits the surface. But, everything after that, I agree with contributor Mís response. You are headed for trouble - solve the problem before it bites you.
From contributor A:
60 degrees for everything (incoming air, the surface you are spraying, the surrounding air and surfaces after spraying (drying area). That would be the bottom number for ideal spraying. Every degree you go below is risking the quality of finish.
If you are not that concerned about quality, mistakes (runs/drips, orange peel), and overall finishing time, then spray at 50 degrees. Your finisher is complaining because his job is more difficult and causes him more stress at 50 degrees.