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Blotches all over wood when applying poly after using water based grain filler

1198 Views 3 Replies 4 Participants Last post by  CharlesNeil
I used Aqua Coat Clearn Grain Filler to seal up a table top I made from Peruvian Walnut and Sycamore. The Walnut had VERY deep pores and it took me 6 applications to get them close to level (though they were still showing somewhat). I made this table a long time ago when I was an impatient sander so some of the joins between the sycamore and the walnut were a little sunken in from where I hit it at an angle to even it out. These depressions it seems did not get roughed up after my last application of the grain filler and now that I have applied the first layer of poly (thinned 50% with mineral spirits) the parts that did not get roughed up have a much lighter apperance. So there are blotches from that. Will this go away as I build the poly in a few layers and finally sand it down to a shine or do I need to sand through the poly all the way to the wood again to make sure I dont have any of the water sealer outside of the pores?
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I can't help you but did you scroll down and read the comments and reviews on the page for the product that you posted? They seem to cover a lot of problems they have had but still prefer the product to others and offer solutions.

May or may not help but it is worth a shot. Or, post your question there also. Good luck on your project. larry
I am surprised that walnut needed a pore filler, especially Peruvian walnut. Most of the walnut I have encountered has fine grain and finished beautifully without any filler. Was it grain you were filling, or tearout from a planer?
I'm guessing you had a reaction between the filler and topcoat. Was the filler fully dry before moving on to poly? Uneven sanding can cause this type of issue as you suggest. That is not likely to improve with additional topcoats.
The blotch may go away, at whatever point the mahogany darkens. The issue is you still have a water base grain filler in areas, and its sealing off the wood. Any solvent based product, oil, will react with the wood and darken it some, the Grain filler is not allowing the poly to get to the wood, thus the surrounding areas are darker. Your only recourse is to either wait it out and hope the areas under the grain filler do darken with time, or sand it down, and make sure you have all the grain filler off the surface, you can test by wiping with some mineral spirits, and see if the lighter spots are present .
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