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Water-based poly over paint - problem with streaking

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Forum topic by ErinL posted 03-04-2012 04:07 PM 2710 views 0 times favorited 5 replies Add to Favorites Watch
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ErinL

2 posts in 1029 days


03-04-2012 04:07 PM

Topic tags/keywords: question finishing

Hi! I’ve hit a snag with a project and could use some advice. I have a collection of mismatched MDF bookcases that I have sanded, primed, painted, and let dry for several weeks. I went to finish them with a wipe on polyurethane, applying two coats 3 hours apart. 24 hours later they’re dry, but I can see all of these white streaks and smudges where I wiped on the poly. How can I fix this? Do I need to sand (without stripping down to the paint) and try a different technique to reapply the poly? Or is there a way to buff out the streaks?

The products I have used are:

  • Zinsser 1-2-3 water-based primer (1 coat)
  • Valspar latex porch and floor paint (2 coats)
  • Pro Finisher Polyurethane by Parks – water-based polyurethane for floors – semi-gloss

    I wiped the shelves free of dust and the wiped on the poly with a soft, lint free cloth.

    I really appreciate any suggestions! Thanks!


5 replies so far

View ShipWreck's profile

ShipWreck

536 posts in 2507 days


#1 posted 03-04-2012 11:56 PM

Poly finishes often do not react very well directly over latex without fine sanding. They will cloud, ripple, and create a messy cleanup problem. The best chance of getting good results would be to sand the entire latex covered surfaces with 220 grit. The idea of fine sanding is to break the glossy top barrier of the latex. Once you break that glossy skin, you get a rougher base for the poly to lock on to. It acts like a base coat/clear coat auto finish. Trust me…......it works.

Poly should be applied with a fine bristle brush and loaded up enough to cause a very slight flooding. The smearing looks to be from the cloth.

View Radu's profile

Radu

305 posts in 1798 days


#2 posted 03-05-2012 01:56 AM

I tried to wipe on WB (Minwax) poly just as test. It does show white streaks and smudges. I diluted with water and wiped it on. It looked a lot better. Try it out on a test piece 1st. In your case I’d recommend light sanding of the paint surface exactly as ShipWreck mentioned.

View Clint Searl's profile

Clint Searl

1479 posts in 1116 days


#3 posted 03-10-2012 01:21 AM

Use a brush and be generous. I’ve never had a problem with Varathane waterborne over latex. Just did some yesterday.

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

View joebloe's profile

joebloe

157 posts in 1049 days


#4 posted 03-12-2012 12:15 AM

I agree with ShipWreck and Radu a little sanding between coats ,what I use is a finnishing pad, kind of reminds me of the green pot scrubber my wife has, only it is softer and lasts longer than sand paper.I agree about the soft bristle brush,I just don’t like wipe on poly,haven’t had any luck with it.You said that you applied two coats of poly 3 hrs apart.I think you should have waited longer between coats,my reason is the shelves where already painted,2 coats of paint,tells me that the wood or mdf is sealed,the poly is not going to soak in to the mdf or wood.I wait at least 4-6 hrs between coats on bear wood.I know it feels dry in about 2 hrs,but that is misleading.I have a friend that got the same results on basicly the same thing.He got in a hurry,I would try sanding it down and use brush on water base poly,give it plenty of time to dry. Hope this helps.By the way welcome to Lumber Jocks.

View ErinL's profile

ErinL

2 posts in 1029 days


#5 posted 03-14-2012 02:16 PM

Thanks for the advice. I’m going to troubleshoot that this week and I’ll let you know how it turns out!

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