Messages

Subject:
Using polyurethane...
Response To:
no disagreements ()

David Weaver
When building poly several coats in row, I've always applied them at intervals and skipped sanding. Mind the discussion, this may be a total of 10 items, but none had an issue.

I view the sanding between coats less as a matter of adhesion and more as something that helps make the last coat look good without sanding back a lot.

I do what Mark said for waterborne finishes with crosslinker on guitar, though - the coats are relatively far apart. Then I do the initial wetsanding and buffing of the finish before it's fully cured so that if it's thin somewhere, I can continue to spray. I've never sprayed more on something 2 days old or more.

In terms of reactivity, I had crosslinked finish at one point in the past that seemed to be mostly cured after a day and learned a lesson - I put the top of a case that was rubbed out and to be attached to my first bookcase on top of a trash can. The finish reacted with the garbage bag badly and I had to scrape it off and redo it. The reaction was very thorough (this was a stew mac WB instrument finish that's probably just one of the target products in a different can for more money).

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