Poly -- Spray vs Brush

[BruceR]

Personally I like to spray whenever possible. Spray cans will cost you a fortune so given the choice between spray cans and brush, I'd do brush in a heartbeat.

Spray allows you to get nice even coats very quickly provided you have the technique down and a good location to spray in (minimal dust and good air supply for yourself)

There is nothing wrong with brushing, it just takes a lot longer.

If you decide on water based poly be aware that it has minimal water protection compared to the oil based poly.

-Bruce

[Richard Cranium]

I'm nearing the completion of my first "real" woodworking project a bathroom vanity. So far I am pleased with the results.

I haven't made up my mind how I will apply the polyurethane. Should I brush it on or spray it on? As far as spraying is concerned I haven't thought about buying an HVLP sprayer but I was considering using aerosol cans.

I would like any opinions from those that have been down this path.

Thanks, R.C.

[B a r r y B u r k e J r .]

Wipe it.

Start with a 50/50 mix of poly to mineral spirits and work to about a

70/30 ratio. Use a clean, lint free cloth, which can be stored in a sealed jar or Ziploc bag in between coats.

In 65-70F, midrange humidity conditions, you'll probably be able to get a coat on about every 3 hours or so. You don't need to scuff sand unless you let it dry for more than 12 hours or so. The coats will be thinner than brushing, so expect to do 4-6 coats.

Practice on scrap, keep notes of what you do, and I think you'll like the results.

Barry

[Mike G]

Spray cans can work, Spraying with a gun is a touchy thing. Varnish, unlike shellac or lacquer, does not have a solvent that you can run through the gun to clean it even if it is cured. In other words you had best be diligent about cleaning a gun immediately and thoroughly between coats and after finishing.

Add to that the time it takes varnish to cure out of tack, and even with HVLP you do get some overspray , causing a sticky mist of bits of varnish floating around the shop and spraying varnish with a spray gun can be a not nice experience.

As someone pointed out spray cans can get pricey but they do a fair job. However, if I were you, I would give some consideration to the method outlined in Barry B's response to your post. It's one of my favorite methods of applying varnish and it avoids a lot of what is a problematic finish to apply.

The only real downsize is that it means the coats go on a little thinner and it requires more coats to get the same build. In the long run though, since you essentially side step a lot of the problems of applying varnish, air bubbles, brush marks, drips and sags, it is actually less work.

[Planet USA News]

I have just completed several projects and finished with poly. I've used spray can, brush, foam pad and HVLP sprayer ( the Porter Cable HVLPconversion from Lowes, about $100, couldn't afford a turbine). I obtained good results from all, just depends on how intricate the projects are. If you have a lot of flat open areas the brush or pad works well. If the project has a lot of corners, like bookcases and end tables, the poly will "pile up" in the corners and cause runs and sags if you're not careful. I like the HVLP for jobs like that. The spray cans work very well, it just gets expensive if the project is any size. Whichever way you choose, just use light coats and sand after each dries to remove any imperfections. Don't rush the finish, it may take several days and 2-4 coats to get a good finish. Good luck, Stan

[Richard Cranium]

Thank you for your replys.

Bruce, I'm glad you mentioned the protection factor because I was planning on using a water based poly.

Barry, I'll give your method of the 50/50 mix a try on some scrap. That's one method I hadn't considered.

Thanks again, R.C.

[B a r r y B u r k e J r .]

I don't know if it will work with water based poly. I've only thinned solvent based poly, and don't know how WB will react thinned down. Check your label before you do it, many water based products don't like to be thinned.

Barry

[Bay Area Dave]

Barry, is correct on the thinning; don't thin water borne poly. It's ok to thin solvent based poly, but the water borne polys caution against it. get a flow out conditioner if you need to reduce it.

dave

Richard Cranium wrote:

[Richard Cranium]

Barry,

Maybe I wasn't clear enough. What I meant was I was planning on using water based poly until I read Bruces' reminder of the greater protection with a solvent based poly over that of water based poly. Now I will definitely use a solvent based poly instead to achieve the greater protection.

Thanks for looking out for me so I don't make any more dumb mistakes than I already have. :-)

R.C.

[Greg]

I was under the impression (based on the book "Understanding Wood Finishes") that sanding between coats of poly was an absolute necessity in order for each subsequent coat to bond to the previous, not to just remove imperfections. Like another poster said, poly doesn't have a solvent like laquer or shellac which means it won't meld to a previous coat. Can someone confirm this in case I'm doing a lot of unneeded sanding between coats?

Thanks, Greg

[B a r r y B u r k e J r .]

Read the can.

Poly is sticky for a bit, where it can be recoated without sanding.

Barry

[Greg]

I've never noticed that. Thanks, Barry! Greg