Topcoats with Oil-Based Poly

[Ryan Swanson]

I am working through finishing some built-ins and bookshelves and need a little help.

Based on great advice here, I've gone through the following schedule on Maple Ply.

Dye
Shellac
Water-based Stain
Oil-Based Poly

My problem is now the Poly holds it's bubbles...and there are enough of them for it to be an issue. With coat one, I sanded them out with 220 and put another coat on...bubbles in the second coat too.

I am wondering if at this point my best bet for a topcoat might be to sand out the bubbles again and use a 1:1 thinned topcoat and wipe it on. I have zero experience with wiping on Poly so I don't know if this is a completely bubble-free application, and/or if this would or would not be smart as a topcoat. Seems logical, though.

Thoughts?


Edit to add that this does not need to be a PERFECT finish, but I definitely don't like speckies.

It's a satin Poly, too...so no high gloss buffing.

[Prashun Patel]

Wiping will make it easier to apply, but it'll take more coats. There's not much of a learning curve, just resist the temptation to a) lay it on thick, or to b) keep working the surface with your rag; You should wipe it on fairly quickly, swipe it a couple times to even it out, and let it be.

Common reason for bubbles:

- Bad brush; some people get bubbles with foam brushes - others don't.
- Pushing on brush too hard
- Squeezing brush out in the can too hard
- Shaking the finish
- Brushing on too thick of a coat

You know, you can also brush varnish that's been thinned a little with spirits (like 1/2 way to wiping varnish consistency). The extra solvent extends the dry time and hence gives bubbles time to work out and pop. That's why even if yr wiping, sometimes you'll see a tiny trail of teeny bubbles. Don't sweat those; they'll pop.

Resist the temptation to reuse yr wiping rag for more than a couple coats.

[Tom Veatch]

First, assuming I have a strong point at all, finishing is certainly not it. But, I've never experienced bubbles with wiping poly. So that could be a workable solution.

Although wiping on a couple of layers might solve the problem, I've not had a bubble problem brushing poly, either. I'm wondering if something about the handling, materials, tools, environment, or technique might be causing the bubbles.

[Ryan Swanson]

Bear in mind there are already 2 coats of 90% strength poly on there, so build-up won't be much of an issue at this point I would not think...just kind of like icing on the proverbial cake.