Spraying waterbased polyurethane

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Forum topic by MichaelTT posted 01-16-2021 12:12 AM 704 views 0 times favorited 12 replies Add to Favorites Watch
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39 posts in 1094 days

01-16-2021 12:12 AM

So, I am about to take my first steps into spraying instead of brushing on my finish.
I have a set of spray guns, the set Jonathan Katz Moses recommends in this video :

I usually use Varathane poly, both the oil based and water based.
I have no special preference for Varathane, it’s just that it is what they sell at my HD very close to me.
From what I can find on the web, apparently water based is better for spraying, but what I can’t find out, if you can use it straight out of the can, or would you have to dilute it ?

Thanks for any tips,

12 replies so far

View Jimarco's profile


42 posts in 2115 days

#1 posted 01-16-2021 01:10 AM

Hey Michael I watched the video and that is a good one to get you started. The middle of the 3 gun set, the one he used is the one for a clear finish. I spray Minwax oil modified poly and there is no need to thin it. If you haven’t used your spray guns I would put the same finish in all 3 guns and spray them to see the difference that they give. I use a 1.5mm tip and a 1.0mm tip… both work fine.

View iminmyshop's profile


371 posts in 3002 days

#2 posted 01-16-2021 02:14 AM

Whatever you choose to do, practice it first on a piece of wood you don’t care about. Make your first mistakes there. How dilute the fluid needs to be may depend in part on your sprayer and the nozzle size not just the finish itself. To establish flow rate, I always spray onto a piece of cardboard first.


View MichaelTT's profile


39 posts in 1094 days

#3 posted 01-16-2021 03:17 AM

Thanks for the answers, good advice !

I do have some experience with spraying paint, I painted a car once, but that was a long time ago, with different materials, and not HVLP.

And yes, I was planning on testing on a piece of cardboard first.

View Dark_Lightning's profile


4437 posts in 4117 days

#4 posted 01-16-2021 03:35 AM

I’ve diluted water-based poly and sprayed it with good results. I’ve also used an old handkerchief and applied a diluted solution by hand with good results. I did that hand application in ‘97, but never posted the project, because I joined here about 10 years ago. You just have to play with it a bit, like any other finish.

-- Steven.......Random Orbital Nailer

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Fred Hargis

6831 posts in 3502 days

#5 posted 01-16-2021 11:55 AM

Generally speaking, most of the water borne finishes are made to be applied one way or another. They are for spraying, or they are for brushing, etc. Thinning them like an oil based finishes (adding whatever is needed for the correct flow) is likely to cause some problems. You can thin them, but the manufacturers usually state a limit (normally 10% or so) on the label. Thinning too much can upset their chemistry, which is a little different than other finishes.

-- Our village hasn't lost it's idiot, he was elected to congress.

View bilyo's profile


1301 posts in 2111 days

#6 posted 01-16-2021 04:11 PM

Like you I generally go to the Varathane WB because it is readily available locally. This past summer, I sprayed a couple of pieces of furniture with it using an inexpensive LPLV gun with a 1.5mm tip without any thinning. I think I got good results and I am not very experienced with spraying. The finish went down smoothly with no runs or orange peal. I have also used the Polycrylic product using the same gun and no thinning with good results.

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4669 posts in 2231 days

#7 posted 01-18-2021 12:38 AM

Quite soem time ago I used an old auto paint sprayer and the Minwax WB poly. Worked fine!

View BurlyBob's profile


8482 posts in 3274 days

#8 posted 01-18-2021 05:05 AM

I used a WB Poly on my kitchen cabinets. I was advised to thin it by 1/3. It worked out fine.

View gtrgeo's profile


150 posts in 1439 days

#9 posted 01-18-2021 06:55 AM

I have sprayed General Finishes high performance poly a few times using the cheap Harbor Freight purple HVLP gun. I used it straight from the can and am very pleased with how it comes out. Now that I have learned a little more about using an HVLP gun I think I could probably reduce the overspray more than I had been.

Good luck. I have used varithane water based poly before and it seemed similar in consistency. Cleanup of the gun is also easier with water based finish.

View xedos's profile


208 posts in 309 days

#10 posted 01-18-2021 03:46 PM

Waterborne is not inherently better -or- worse than solvent/oil based finishes. They all have benefits and drawbacks.

Availability and support in your neighborhood will be a huge factor. No sense choosing a material that you can only have delivered from cross country, or buy 5 gallons at a time if you’re a hobbyist.

Thinning is as Fred says – maybe you can , maybe you can’t. The material TDS will tell you if you can, and how much. Most waterborne finishes can only be thinned 10%. That’s not much. If it won’t spray at that reduction, you have to get more pressure and/or a larger needle size for your rig.

Don’t test on cardboard, unless you’re finishing cardboard. You can setup your spray pattern on the cardboard, but you’re test needs to be on the same material you’re finishing.

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Jeff Vicenzi

63 posts in 398 days

#11 posted 01-27-2021 10:43 PM

I’ve spray a lot of water base poly. Be aware that Varathane water based poly has no where near the durability of a typical oil based poly. If you want a water base that sprays well and has good durability, I’d suggest either ZAR OMU or Target EM8000. If you don’t need real high durability, I’ve found that Minwax polycrylic sprays very well with durability similar to Varathane water based poly.
For best depth of color, I’d recommend sealing the wood first with a coat of shellac. I do not recommend any water based product on natural cherry… it develops an ugly color.

View ChefHDAN's profile


1802 posts in 3858 days

#12 posted 01-28-2021 02:51 PM

It is not popular here to admit it but, I will, most all of my pieces get finished with WB poly. I have the $20 HF gun and have results that I am very pleased with. For the most part I shoot Minwax WB Poly in the light blue can and I shoot it straight out of the the can. Depending on the weather, I usually shoot in my driveway and can get about three coats in a setting. I’ll use 320 or 400 to knock down the finish and then apply 2 to 3 more coats. On final finish I use Johnson’s paste wax with a 0000 steel wool to apply. I get a very good bulletproof final finish that, to me, does not have the plastic finish that many describe. 99% of what I’m finishing lives in or around kids & I hate having to fix a finish so WB poly is a great go to. As for a cherry finish, I go for about 6 coats of BLO and allow 7 t 10 days in the summer for the BLO to cure before WB finish, all of my cherry projects are finished this way the hall table project I actually updated with a pic several years later to show the aged cherry… it’s gorgeous to me but.. its just my opinion.

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

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