Spraying Water-Based Finishes in Cold Weather

      Here's solid advice on maintaining good temperature conditions for spray finishing, without wasting heating energy. December 15, 2005

Winter is rearing its ugly head. I'm looking for any suggestions on spraying WB on cold days. I heat with an 80k hot air propane heater. The spray fan sucks the shop heat dry in minutes. Do the catalyzed solvent based finishes work better in cold temps?
Last year I switched over to just pre-primed (BIN sprays down to 0 degrees). I need at the very least a clear coat (other than shellac) to spray in cold weather. I do not care about dry times, just product failure.

Forum Responses
(Finishing Forum)
If you can, set up a drying room. Bring your components into the room a few hours or overnight before you intend to spray them. This will warm the parts up to whatever temp your spray requires (77F?). Then bring your parts out into the cold area and spray them. Then bring them back into the drying area to flash and dry. The few moments of cold won't affect the spray(ing). And bringing them into the warm area will keep them at the proper temperature to dry correctly.

The above response is good. Also keep the finish itself warm prior to and during spraying. I have heard people use those heating pads wrapped around the pressure pot to keep it warm. (If you use a pot.)

I've heard of some people putting their gallon of finish in hot water. But unless you have a warm surface, as mentioned above, this would not help... correct?

Kremlin, and I am sure others, sells an in-line heater that would give you more reliably warmed material.

You don't have to go to extremes like heating the finish or the items to be finished. Try to keep your shop/spray room as warm as possible, of course. You don't want the stuff to freeze in the bucket, but all you need to spray and not get terrible results is 65 degrees. The warmer the better, sure. Dry time is a little slower, but if you're not in a real dusty environment, it's not too bad. Halogen lights will heat up an area pretty quick and give you more light. We try to do any sanding or staining early in the morning and the place can be heating up while we're getting ready to spray. It doesn't take a lot to get up to 65-70 degrees.

If you can't set up a drying room, perhaps you can seal off the booth and have a duct supplying it with cold outside air so you don't suck the shop's warm air out. As long as your parts are warm before and after you spray them, working in a subzero booth is more of an issue for the operator than the finish. As far as the 68 degree rule for MLC CVs, their lab told me that it doesn't need that temperature for 8 hours directly after being sprayed, but within a few days to allow a substantial cure, so don't worry if you are spraying Friday and cooling the shop and it doesn't get to 68 until Saturday afternoon.

Did MLC tell you how long the CV needs to be at 68 or higher? Just curious, because sometimes I have cabinets that sit in the finish room for a couple weeks before they get installed and I'd like to conserve some energy.

My impression was that a total of 8 hours at 68 degrees would be necessary even if spread over some time, although you should contact them to get more precise info. Get past their customer service and penetrate their lab, which is very helpful - you can talk to the formulators.

For instance, I recently learned that you can add over 20% microton dye to a tone coat and not cause a problem. They also described a way around sandwiching their oil based glaze between vinyl - dilute the glaze 2 parts mineral spirits to 3 parts glaze, apply, wait for the application to lose its sheen (1-2 hours) and topcoat directly with Krystal, Magnamax, etc. I tried it and had no problems (the thinner cuts the linseed oil in the glaze), although if you're leaving a lot of glaze on, it's cheap insurance to shoot a coat of vinyl. Get to their lab or get your local rep to - mine is great. Perhaps these items are common knowledge, but they are in direct contradiction to what you will hear if you talk to MLC customer service.

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