Thread: Oil based polyurethane problem on pine

I've used oil-based polyurethane many times on many timbers. Some of my conclusions are

Use high quality expensive brushes. Clean them very very thoroughly after use and they give great service.
They also give a superior finish.

Many thin coats. Starting with a slightly thinned poly, then building coats over the top. Depending on your circumstances, temperature, humidity, composition, a light sanding after 12-24 hours, then applying the next coat. If you leave it too long, the poly will harden to the point where the next coat will not adhere well. But you also have to give it enough time to set.

Long strokes, with the brush not too wet. Spread it out. Don't go over what you just varnished a second time with a wet brush several minutes later, make sure to keep a 'wet edge'.

On fresh timber that hasn't had a finish on it before I count on 6-9 coats. Really the quality of your finish depends on how much elbow grease you invest here.
I've never buffed. If I made a boo-boo, I sand a bit more and do it over.

In my personal opinion oil based is much superior to water based polys. I've had the waterbased stuff wreck my brushes after one single use (could not wash it out of the natural bristles) so I ended up having to use synthetic brushes that just don't give the same quality finish. It's dull by comparison i.m.o. --- maybe it's down to a knack of application though.

I can see there are two problems.
I am going over the same area twice and it leaves smudges. The reason for that is because the surface kept soaking up the initial layer. What grade of sanding paper are you using and is it manual or power sanding?

I always use a sanding sealer which seals the uneven absorption of timbers such as pine etc in one coat, where it can take at least 2 coats with the poly topcoat.

Also much easier to sand and doesn't clog the sand paper like the poly topcoat.

I might try that

I had same problem and in frustration I used a short knap roller, and sanded with 400 wet and dry between coats. Far better finish than with the brush.

Yeah I might try rollers as well since I can have some, but I might also try to thin the poly as it seems rather thick and dries pretty quick. So it's hard to avoid brush marks

as P.W.H. advised -- use a quality natural bristle brush

also how hot and dry is it where you are finishing?

unless its the first coat, I'd keep thinning to around maybe 1% if it's really hot and dry

Discovered a long time ago that pine is notorious for patchy finishes and blotchy finishes unless a sealer is used first. I usually use a Feast Watson sealer with good results, others, I believe use thinned shellac as a sealer.

As has been stated, good brushes are essential, that being said, I have had good results with rollers on large areas like tabletops and benches.

Didn't get a chance to use sanding sealer for this job. Maybe next time. Decided to use a short nap roller, worked out much better than a foam brush. I would only recommend using a brush for hard to reach corners otherwise a mini roller is just much quicker and smoother.

Glad it worked out for you.

Also check out a product called Penetrol. It's an additive that greatly reduces brush and lap marks by improving the flow out qualities.

Wipe down with turps prior to the first coat, leave for a few minutes then wipe off excess then apply your first coat.