# Spraying polyurethane with hvlp rig?



## Zipperjack (Apr 5, 2013)

I just got my hvlp spray rig and was wondering if I need to thin polyurethane before trying to spray it. Gonna use minwax high gloss poly


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## HowardAcheson (Nov 25, 2011)

Oil based varnishes are not a good finish to spray. They dry so slowly that the overspray is in the form of liquid mist. The mist floats around the shop and gets on to everything. When it dries you will have a crust of finish on everything. If you want to spray an oil based finish you need a good, effective spray booth.

Fast drying finishes are the things you want. Finishes like shellac, lacquer and waterbornes spray well.

If you are new to spraying, let me strongly suggest you get some cardboard boxes and practice spraying on them. Don't spray a real item until you are satisfied that you can lay down a good finish.

I good book like Charron's Spray Finishing will get you down the road faster. It will explain the equipment and how to set it up and adjust it. It will talk about how to thin the products. And, finally, it will explain how to spray a smooth finish.


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## Steve Neul (Sep 2, 2011)

It helps when spraying oil base polyurethane if you would thin it with naphtha when thinning is needed. It also makes the finish take longer to dry and more prone to run the more you thin it. I will first try to spray it without thinning it at all before adding anything to it and then just enough to get it to spray. Overspray is an issue. Spraying indoors you pretty much need to improvise a spray booth. I sometimes will spray it outdoors when there is no wind. It's difficult to get used to spraying poly thick. It looks bad with orange peal when it's going on but the finish dries slow enough it flows out after a few minutes and looks fine.


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## retfr8flyr (Aug 7, 2013)

I do my spraying inside and I don't have a separate spray booth, so I only use WB finishes. I have had good success with Minwax Polycrylic http://www.minwax.com/wood-products...-finishes/minwax-polycrylic-protective-finish with my Earlex 6900 HVLP spray setup. I spray this with the 2.0 needle straight from the can, without any thinning. It goes on very nice with good coverage.


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## Zipperjack (Apr 5, 2013)

retfr8flyr said:


> I do my spraying inside and I don't have a separate spray booth, so I only use WB finishes. I have had good success with Minwax Polycrylic http://www.minwax.com/wood-products/interior-clear-protective-finishes/minwax-polycrylic-protective-finish with my Earlex 6900 HVLP spray setup. I spray this with the 2.0 needle straight from the can, without any thinning. It goes on very nice with good coverage.


I tried some polycrylic last night just playing around I think I like it went on very well and it doesn't smell as bad as oil based stuff


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## cabinetman (Jul 5, 2007)

Zipperjack said:


> I tried some polycrylic last night just playing around I think I like it went on very well and it doesn't smell as bad as oil based stuff


It's pretty easy to spray. Don't load up an application, or let it puddle or pool. Try to spray items vertically. Work with a lot of light so you can see how wet your application gets.








 







.


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## Fred Hargis (Apr 28, 2012)

I'll second the headaches from spraying the oil based varnishes. Regardless, if you want to try it you will most certainly have to thin it.


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## chuckha62 (Mar 27, 2014)

I spray Polyurethene all of the time. It does take a bit of technique and thought to keep the finish smooth and the overspray down, but it looks great. If I thin, I thin with Lacquer thinner and never exceed 10%. If I exceed 10%, the finish tends to change sheen.


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## Steve Neul (Sep 2, 2011)

chuckha62 said:


> I spray Polyurethene all of the time. It does take a bit of technique and thought to keep the finish smooth and the overspray down, but it looks great. If I thin, I thin with Lacquer thinner and never exceed 10%. If I exceed 10%, the finish tends to change sheen.


I was curious how long you have been using lacquer thinner to thin poly. There is enough chatter on the net I'm sure it works but I was wondering what the long term effects it would have on the finish. The paint manufacturers don't recommend any solvent stronger than naphtha.


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## chuckha62 (Mar 27, 2014)

Steve Neul said:


> I was curious how long you have been using lacquer thinner to thin poly. There is enough chatter on the net I'm sure it works but I was wondering what the long term effects it would have on the finish. The paint manufacturers don't recommend any solvent stronger than naphtha.


I tried it first about three and a half years ago. I wasn't sure I could, but tried it on some test pieces, it worked fine. I've now produced countless pieces and so far not one customer complaint or return.

Now, full disclosure: This is on indoor pieces ONLY. Anything that is going to be outdoors, I use Cetol, by Sikkens and (knock wood!) it's been holding up very well. We'll see how it holds up as pieces age.

Chuck


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