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can i spray poly???

woodlicker's picture

i been working with a lot of jarrah, a hard wood from ast. and it looks great with just polyurethane which i been buying in spray cans, but at $7.00 a can its time for a change. can and how do you spray polyurethane? thank you for any addvice...larry

SteveSchoene's picture

“Poly” as a term (post #154112, reply #1 of 9)

“Poly” as a term doesn’t tell us much about what you want to spray, or what you have been spraying.  What kind of poly have you gotten in the spray cans—brand and name?  If you mean an oil based varnish, then you can spray, but the varnish formulated for brushing dries so slowly that overspray can be a problem, both in making a sticky mess over the entire area, and unless there is sufficient air movement over the object being sprayed creating problems when it settles on the surface.

Test your finish on scrap, FIRST, or risk having to scrap your finish.

woodlicker's picture

minwax polyurethane (post #154112, reply #2 of 9)

 i have been using MINWAX POLYURETHANE in aresol can. i would like to buy it in gallon cans and use air sprayer. the problem is i cant find anywhere to get advice that even mentions polyurethane or if you can use it in  a paint sprayer...i asume that if to comes in a spray you should be able to. thanks for the replies...larry

SteveSchoene's picture

I assume you mean Minwax Fast (post #154112, reply #4 of 9)

I assume you mean Minwax Fast Drying Polyurethane.   The liquid varnish will not behave exactly like the aerosol.  Minwax isn't very forthcoming with ingredients, but the liquid is thinned with mineral spirits which evaporate much more slowly than the acetone that makes up the bulk of thinner for the aerosol version.  We can't tell about differences in the resin formulation and additives, but they may well exist. 

There are finishes more suitable for spray application than oil based varnish such as the Minwax.  Unfortunately, those with durability properties similar to the varnish require spray facilities that can manage the flammable and often toxic solvents that those require.  If you don't need the protective properties of an oil based varnish, there are waterborne finishes that spray quite well and don't require the specialized facilities. 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

woodlicker's picture

polycrylic???? (post #154112, reply #5 of 9)

thank you steve but, im still lost on what to try. the fast-drying polyurethane (clear gloss i should have mentioned) gives me beautiful finish. i do not want a stain or varnish that would change the color of the peice. most everything i make stays inside so weather is not concern but mabe water on a table or plant stand ect. could be, all i want is a clear shinny, protective finish...dont mean to be a pain in the neck and i do thank you or anybody for your ideals or opinion. its nice to know you folks will take time to answer ?'s for the dummies like me that sometimes just dont know what we want ...thanks again...larry

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3fingerjack's picture

Woodworking e-Books (post #154112, reply #3 of 9)

If you're interested you can download an e-book on spray finishing from the Taunton store. Here is a link to it:

http://store.taunton.com/onlinestore/item/spray-finishing-andy-charron-ebook-077919.html

It might get you started in the right direction.

"There are some ideas so wrong that only a very intelligent person could believe in them." George Orwell

screename56's picture

Spraying Minwax Poly (post #154112, reply #6 of 9)

Larry,

Yes, you can spray Minwax Polyurethane.  I have sprayed it myself and it turned out beautiful. My spray equipment consist of an air compressor with a 60 gallon tank with a 3hp motor, and a spray gun from CATechnologies.  They have both served me well in my one man shop. I used the Satin finish but this is only a personal preference. It does take longer to dry than lacquer, however, if you can control the dust a little bit , it will dry nicely.   Be sure to follow the directions on recoating.  You will need to wait a few hours.  Lacquer can be 2nd coated in about 45 minutes.  If you will use a 600 grit wet sandpaper on the poly a day or two after it dries, it will remove all of the very small dust particles that may stick to it during the course of drying and will be incredibly smooth.  I usually will splash a few drops of water with my fingers on the piece just before I use the sandpaper and wipe it off immediately afterwards.  I did thin the poly about 10%  with mineral spiritsbefore spraying and it did nicely.  Prior to spraying the poly the first time, I went on-line to Minwax.com and asked the same question you asked.  Their response was useless.  All they said was "why do you want to spray it?  I explained the particular situation and they never responded back. I f you read the can , it does not state anything either.  I prefer lacquer over poly because it drys much faster, however, sometimes I still have to use the polyurethane.  It is a good product and will dry to touch in a couple of hours, so the amount of dust is minimal unless the wind may kick it up some.  This post will probably get to you too late but may be helpful to others.

Good Luck, Screename 56

PCM's picture

spraying Minwax fastdry poly (post #154112, reply #7 of 9)

Larry,

I have been spraying Minwax f.d. poly for years, with good results. My equip. is a HVLP sprayer in a spray booth. I spray 2 coats of gloss, followed by a final coat of the sheen desired (satin, semi-gloss, gloss). This routine prevents a cloudy/plastic  look.

I sand the 1st/2nd coats with a superfine foam sanding pad from 3M. The final coat is buffed out with a piece of brown kraft paper (grocery sack). Listen for "squeaks" when using the paper sack, because that will tell you there are micro "corms" forming because the poly is not sufficiently dry.

In the recent past I have noticed that the poly formula  has changed-i.e. it sprays thicker and does not flow as well as it used to. I do not thin with min. spirits, may have to start. If I start thinning, I will test different viscosities. I will actually need to but a viscosity measure, or something similar. I will probably contact Jeff Jewitt of Homesteadfinishing.com, for advice.

Another source for info might be Howard Acheson, who in the past on this forum has said he teaches Minwax courses (or some such). I do not know how to contact him thru Knots, other computer guru's may.

Hope this helps.

Pete   

woodlicker's picture

thank you for your (post #154112, reply #8 of 9)

thank you for your information, i to went to minwax's web sight which i thought was fairly impressive how ever after three times asking the same thing, including e-mails to them with no anwser i just gave up. thanks again...larry

ubc's picture

spraying poly (post #154112, reply #9 of 9)

I just did a small stair job replacing an oak tread. I sprayed Minwax poly with a Jaugar HVLP gravity gun. Three coats of silky smooth perfection.