Applying finish outdoors under a canopy

[Jerome Hanby]

I don't have room indoors to apply finish to anything very large. Living in Birmingham, Al the Summer afternoons are always a crap shoot when it comes to rain. My wife came up with the idea of getting one of those canopies like folks use for tailgating to use when we are applying finish outdoors. I thought about going with a model with the screened in sides to keep bugs, leaves and pets away from the drying pieces. Given the high temperatures (pushing 100) and high humidity (some days also pushing 100!), you guys think this could be a workable solution? Our go to finish is shellac, but we also have some projects that will be using danish oil and Brelen's Rock Hard. We also use Tung oil, but mostly on turned items and it's applied while items are still on the lathe, so those are in the garage/shop but the doors are open so practically outside. Haven been looking at the entry level HVLP setups and this has us thinking about a finishing area that would be outside and not need additional ventilation.

[Prashun Patel]

If the awning will keep it cooler, then you can make it work. I'd finish in the evenings or morning, though, and avoid the heat of the day.

[Jerome Hanby]

In the summer, I try to get a jump start early in the morning, but the finish would still be in the drying stage during the day. Blocking the direct sunlight would help a bit, but I don't see how it could be less than 85-90, unless it rains. How big a problem is the high humidity?

Thanks for the feedback!


If the awning will keep it cooler, then you can make it work. I'd finish in the evenings or morning, though, and avoid the heat of the day.

[Prashun Patel]

Honestly, I've applied shellac under these conditions. I believe it to be a problem only on slower drying varnishes when applied thicker. But I'm a bit out of my league on this; all I can say is that it should not be a problem with shellac and some varnishes.

[Harvey Pascoe]

I'm in north Florida and I do all my spraying outside year round. In cold months the work is brought in to dry, but in warm weather they stay outside to dry. I just have to constantly keep an eye on the radar and the sky because a canopy does not prevent rain from being blown in under it, really no matter how big it is. Besides, an approaching T-storm usually kicks up dust before the rain.

Heat is a big plus, humidity doesn't seem to matter so much, its always high at around 80%. Another problem is that bugs LOVE varnish and think its the perfect place to land.

[Howard Acheson]

Most manufacturers state their oil based finish's working conditions to be 65-75 degrees and 50% relative humidity. Temperatures above 80-85 degrees and RH of 85% are the upper limits for most oil based finishes. Waterborne finishes can be problematic if the RH is above 85%. Shellac and solvent based lacquer can be applied in most any temperature and humidity.

[Jerome Hanby]

Sounds like the best bet is to do all the stuff I tend to do finish wise outside (shellac and solvent based), and carry stuff inside and setup on drop cloths for stuff my wife handles (the stuff that actually looks good).

[Harvey Pascoe]

Honestly, I've applied shellac under these conditions. I believe it to be a problem only on slower drying varnishes when applied thicker. But I'm a bit out of my league on this; all I can say is that it should not be a problem with shellac and some varnishes.

I just shot some alkyd and poly varnish at 92 degrees and around 80+% humidity and left them in the sun to dry where the pieces got quite hot. The poly dried to handle within an hour whereas the alkyd was four hours to touch dry - really quite slow - so I brought it into a/c and the curing speeded up, so I definitely think real high humidity is a problem for only alkyd and not advanced by heat when the humidity is that high. Alkyd dries considerably faster when the humidity is lower. Water based slows down a bit under those conditions but they dry so fast that a delay of 30 minutes or so is no big deal to me.

If I believed everything written on the can, I would probably go broke.

[Sam Hamory]

I live in Fla. and sprayed with HVLP for over twenty years under a tarp style carport with net sides. Works great, always watch the weather!