Refinishing my kitchen table. The process so far: strip, sand (progressively moving through the grits), condition, stain, finish, sand,'finish again. Any ideas as to why a coat of Oil-based polyurethane is separating in small circles within a few minutes after its applied? I've sanded and resanded, and if anything it's getting worse. Once the coat dries, there are several small "holes" or "divets" where the polyurethane didn't take and instead, crawled away from those spots. What did I do wrong? I didn't notice the separating with the first coat of finish, but with the following coats. Is there any way to fix this?
A couple possibilities come to mind:
- The product was not mixed well
- The product has exceeded its viable shelf life
- The product is contaminated
- The table surface contains contamination
- The table is made from a very oily wood that the varnish is not bonding well too
- Applying it with the wrong applicator
- Other application issues - wrong solvent used to thin it, applied too thick, etc.
I would start by ruling out the varnish as the issue by trying another can, manufacture, etc.
If it turns out the wood is the problem, you might also try applying a thin layer of a dewaxed shellac as a sanding sealer first. More difficult woods might require something like Clear Penetrating Epoxy Sealer or a Hardwood Epoxy Glue as a base layer to the varnish.
I have no affiliation with these products and only recommend them based on experience
I've had this experience with water based poly but not oil... so I don't know if this is the right advice, but maybe your first coat was good and thick. When I had that problem, my solution was to sand it all down and use a thin watery coat, more like a primer for the second thicker coat. This helped in my situation with polyurethane "pooling" on the surface.
Of course with oil based poly you would want to use naptha or a commercial (blended) product for thinning.
Also, you should try using about 120 to 200 grit paper for your in-between coat sandings... supposedly, it's not helpful for bonding, but contrarily, it's not harmful either.