Had my first experience with this material on a laundry sink countertop I glued up out of some really nice redwood I salvaged from an old hot tub. The wood was well seasoned (many years old) plus it sat around my shop for some time after being milled straight and flat. Don’t think there was any residual contamination on or in the wood that would have caused this failure.
Moved the cabinet up to our new house last weekend and in the process managed to scratch the top in one small place. Absent mindedly I took my fingernail and scraped on the edge of the ding …. the finish literally comes off with my fingernail. This is after about three weeks of curing time for four coats of the material.
I realize I’m in for a complete scraping removal of the old finish back down to bare wood. I’m wondering if this is a poor choice for this kind of material of if I made any mistakes in application or preparation of the base material. It was brush applied and each coat was allowed to dry for the prescribed time before the next coat. No sanding between coats other than a light scuffing to remove the few innescapable dust speck from my less than clean shop area.
Thanks for any ideas….
Replies
It doesn't sound as if you did anything wrong. I've used lots of waterborne poly, but not on redwood. That could be your problem.
When I've used it on ash, alder, oak, or any other wood, it has done well as far as sticking to the wood. The drawback with it is that it will scratch in a very unsightly way. When it does, there's no way to repair it short of taking it all off and starting again. Without getting into a song-and-dance about the molecular bonding during the final cure, let's just say that it is hard, and hence, brittle. Think about hard steel and how it chips but doesn't bend.
As far as getting it to stick well to redwood, you might want to seal it with shellac or something before starting to apply the poly, but that is a w.a.g. on my part.
I've usually followed the rule of thumb that if you don't wait more than 24 hours between coats, you don't even have to scuff the previous coat. My shop is not too clean, either, but since I spray the poly in fairly thin coats, I've never been troubled by gunge sticking to the wet surface. I use a HVLP gun with a regulator on the gun set to about 12 - 15 psi, and a compressor.
When I switched from conventional stains and finishes to waterborne, I had the devil's own time getting used to it. You kind of have to learn to think in a different way; most of your knowledge of solvent based stuff is wrong when you use waterborne.
Hope this helps.
Enery VIII
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