Water based and humidity

[Peter Quadarella]

OK, so I'm very seriously considering buying an HVLP turbine (Earlex 5000) and was hoping someone could help me make sure I'm not making a mistake. I live in North Carolina, and it is fairly hot and humid a lot of the time. I work out of my unheated, uninsulated garage. I can finish in there, or in the driveway, but either way there's no way to escape the heat for much of the year.

Will it be a mistake to start spraying water based stuff in this environment?

Also, as a corollary - if I put on some oil and shellac for color before doing the water-based, am I gaining anything here? Is it too dangerous for me to spray shellac?

My goal in all this is to make finishing easier and quicker. I am really not good at it, don't enjoy it too much, and don't have a lot of time to devote to getting better. I'm willing to do what's necessary, but am looking for a shortcut and am hoping spraying will be that for me. Thanks for any advice!

[Jason Roehl]

If you can pick your spray times carefully, it's not a problem. You just need to avoid the highest humidities--like above about 80 or 90% RH. Higher heat can help alleviate the humidity problem, but it can also mean that things dry too fast and you'll have problems with "dry spray"--overspray that settles back on the piece in an already-near-dry state and acts like very tenacious dust, then. Dewaxed shellac is an excellent thing to put under waterborne poly, in my experience, but it, too, is susceptible to high-humidity problems (it may blush if you trap too much moisture underneath it). Also, breezy conditions may aid with drying, but they are a bear to spray in, and if things are drying slow, you'll end up with all kinds of c|?@p in the finish.

When I spray anything, I tend to go for quicker, thinner coats up front so that I can recoat much sooner, pushing the finishing schedule a bit, then my last coat of the day/project might be a little thicker to help with the self-leveling properties of the finish.

All that said, with all the spraying I've done, in all extremes of conditions (I once sprayed a coat of industrial waterborne inside a concrete building that was at about 50ºF, came back 24 hours later on a cool/rainy/humid day and it was as if I had just put it on), and I would much rather have quick-dry conditions when spraying. If it's drying too fast, I'll use more material or get a bigger sprayer, but quick-dry means that the window of time for things to go wrong when you turn off the sprayer is small.

[Peter Quadarella]

Thanks Jason. I'm not usually in a rush to finish anything so if I just pick my times properly it sounds like it won't be an issue.

[Jason Roehl]

I forgot to mention that the bottom line is it takes practice. I know many guys memorize settings and all that, I go on experience--I have many, many hours behind sprayguns, most of that airless, but some HVLP, too. A piece of cardboard or plywood for testing your spray pattern is invaluable. With an airless, I'll have in mind a tip size or two depending on the task and material I'm spraying ahead of time, and adjust pressure part by visible spray pattern, and part by what it sounds like!

Jason