Oil Poly Problem

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Forum topic by rbk28 posted 09-02-2014 05:03 PM 847 views 0 times favorited 11 replies Add to Favorites Watch
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5 posts in 779 days

09-02-2014 05:03 PM

Topic tags/keywords: question spray gun finishing

Hi Everyone,
I have some background with brush finishing, but new to spraying. I originally finished several doors with Minwax Oil Based Spar Poly (brush) and was not completely satisfied with the results. I’ve always wanted to get into spraying and thought this would be the best project to learn. I bought a Titan 105 HVLP and seems to be a great setup. I sanded down my doors and people at sherman williams recommended spraying the same poly since it was already on there. I am having very inconsistent results. I set up a small booth in my garage with a dehumidifier and my hygrometer has been reading 50-60%. Some of the portions of the doors have been perfect, but others are getting hazy marks and gatoring is the biggest issue. The doors are 3 panel- am I getting too much product on where its gatoring? I’ve tried experimenting thinnning slightly vs thinning more and results seem to be slighty worse with more thinner. I’m considering trying a water based. Is this a better direction to go for self leveling and ease of working with? Secondly, I only have one gun at the moment. I know its ideal to have two separate guns, but would I be able to run water based through the same gun that I spray oil? I clean it thoroughly after each use. I’m starting to get quite frustrated, so any help would greatly be appreciated. Thank-you for reading and happy to be a member here.

11 replies so far

View gfadvm's profile (online now)


14924 posts in 2107 days

#1 posted 09-03-2014 12:40 AM

I have sprayed a lot of MinWax Spar Urethane and never had any “gatoring” problems. I spray it undiluted with a cheapo HD sprayer. I do lay it on pretty thick and it seems to self level. I practiced on cardboard until I got the pressure/air/flow settings right. Then I make sure to duplicate the settings every time I spray. Never sprayed water based.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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5 posts in 779 days

#2 posted 09-03-2014 11:36 PM

Thanks for the reply. I spent alot of time at Sherman Williams spraying store and they concluded that the poly, even though dry to the touch/appearance, wasn’t completely dry underneath (I waited 24 hours). Spraying over a non-dry coat was causing the gatoring. It sounds legitimate to me, so they recommended letting it sit for a few days, then sand it down quite a bit and let it sit for a few more days. Hopefully that will dry it out completely, then I can do my final finish coat. I had 2 doors that were stripped down to bare wood and re-stained, those turned out absolutely beautiful with 3 spray coats. Sheer coincidence? Sherman Williams recommended I stick with the Oil since it already has a few coats on it, but any tips on spraying over a coat that’s been on the door for a year? Is a sealer coat required, then spray?

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14924 posts in 2107 days

#3 posted 09-03-2014 11:42 PM

I have sprayed only MinWax Spar so no experience with SW product. I have sprayed second coat when the first was still tacky and never had wrinkling/gatoring.

I would sand that old finish back to where it was smooth and uniformly dull before respraying the door.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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5 posts in 779 days

#4 posted 09-05-2014 07:57 PM

I am spraying Minwax spar as well. I have sanded the doors down quite a bit and am letting them dry out for a few days. I’m planning on spraying again sunday or monday. I guess I should clarify something. The more I look it, it might not be definitive gatoring, rather the appearance of wet spot streaking throughout. Hopefully I’ll be happy by monday lol.

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133 posts in 2028 days

#5 posted 09-05-2014 09:32 PM

Anything called “spar” will need more drying time than non spar. Spar finishes are soft to allow for environmental changes in the wood without affecting the finish.

-- .. heyoka ..

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13054 posts in 1273 days

#6 posted 09-05-2014 09:51 PM

I’m not familiar with the Titan, but with the earlex, I use a 1.5 needle for finishing and the larger 2.0 for painting. You may be putting too much product out there and not atomizing it as they say. I think the gator ing may be caused by too large of drops hitting the surface and then drying before they can level.

-- Bill M. "People change, walnut doesn't" by Gene.

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4823 posts in 2230 days

#7 posted 09-05-2014 10:33 PM

Switching to a sprayable lacquer will ease the pain considerably. It dries quickly, and you only need two coats. I like Rudd Duracat-V, but Valspar and Sherwin Williams pre-cat lacquers performed well too.
I really dislike Poly, and reserve its use for exterior doors.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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5 posts in 779 days

#8 posted 09-06-2014 12:27 AM

I figured a picture would help. This door wasn’t completely dry, but close enough to see the effect. I’m experiencing more of the effect on the right portion of the door, opposed to the portion on the flat panel.

Firefighter, the smaller needle is an intriguing idea- thinner the coat, less likelihood for error. That thought of over-
spraying has crossed my mind. The most “gatoring” is throughout the flat panels of the doors. I very well could be putting too much product while I’m trying to hit the sides of the panels. Pinto, lacquer would be ideal and is what I wanted to do originally. However, since there is already several coats of oil poly on the doors, lacquer would require me stripping every door down to bare wood. This thought crossed my mind today as well. After the brushing a year ago, I lightly steel wooled with paste wax. Could the sanding be pushing the wax further into the wood and not allowing the poly to dry or adhere underneath the dried surface? Thanks for you help and ideas so far everyone.

View Earlextech's profile


1157 posts in 2107 days

#9 posted 09-08-2014 01:23 PM

That is a case of incompatible finishes. I would start thinking about coating with de-waxed shellac and then the top coat of your choice.

-- Sam Hamory - The project is never finished until its "Finished"!

View BinghamtonEd's profile


2263 posts in 1786 days

#10 posted 09-08-2014 01:36 PM

I had that same outcome a couple of years ago when I applied Minwax oil-based poly (brushed on) over plywood that I had dyed with a water-based dye. The only conclusion I could come to was that the water had not fully evaporated before I applied the poly, even though it had been a few days. I sanded it back, let it sit for a couple weeks while out of town, then reapplied and it came out fine. Sam’s response makes sense to me, and explains what happened to my project.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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5 posts in 779 days

#11 posted 09-08-2014 04:34 PM

I may have figured out a solution. I don’t know the exact cause and all of the above are possible, but last night I scrubbed two doors with paint thinner, let it evaporate, then sprayed, they turned out as they should. I’m assuming letting them dry out for a week probably was a factor too, but I’m thinking it was the paste wax not allowing the urethane to adhere properly. We’ll see how the rest of the doors go, but I’m expecting good results now. Thanks everyone.

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