Finishing Maple and Oak Woodwork

[HomerJ]

I finished an attic space in my Circa 1929 home and am installing woodwork to match the original woodwork in the rest of the house. I am also replacing some of the damaged baseboards and window casings in the rest of the house. It is primarily maple and oak that I am working with.

Anyway, my problem is that I am getting a lot of little bubbles that are drying into the polyurethane and it looks like crap. Any ideas as to what is causing this and how to prevent it? Keep in mind I am a complete novice, so it could be something very basic too.

I am using minwax oil based fast drying polyurethane and just following the instructions on the can. Sand to 180. Stain. Apply thin coat of poly. Sand with 220. Apply second coat (I am assuming it should be thicker because it doesn't explicitly say "thin" coat). Sand with 220, apply third coat.

If I make the third coat thin, it is better, but still not great. I am using a decent brush (Around $8) that is designed specifically for polyurethane. But it seems like the process of brushing it on is what causes the bubbles. Is there a better application method?

Also, considering that I have three dogs and the woodwork can take a beating at times from them, is basic polyurethane the right way to go, or are there any products that are better and where do I get them?

Thanks in advance for your help.

[RufflyRustic]

Hi, In my limited experience, brushing it on can definitely cause the bubbles. Are you able to get a couple of test pieces and try using different applicators to see which gives the result you are looking for?

Are you able to lightly sand down between coats to get rid of the bubbles?

You said an attic - what is the weather like in the attic, bubbles can also come from too much humidity.

As I said, my limited experience, but I have learnt the hard way. Good Luck

Cheers
RufflyRustic

[Justin]

I'd try thinning the product down with whatever the manufacturer recommends, for at least the first coat. Most poly finishes I've worked with are really thick and viscous anyway, so thinning the product down means less brush marks and generally easier application. Of course the downside is that you may need more coats to build the finish up, and you may get runs in the finish if not applied sparingly, but I feel the end result is better.

We don't really see much oak or maple down here in Oz but from what I've read in your magazines, oak is quite open grained (especially red oak). Perhaps this is contributing to your bubbles, and therefore thinning may be the go......

I agree with RufflyRustic's suggestion regarding test pieces. If I'm working with a finish that I've never used before, or putting known finish on a type of wood that I've never applied it to before I ALWAYS do test pieces. Get yourself a few offcuts, and try a few different techniques (such as different thinning ratios) on each piece. It helps if you write what you've done differently on the back of each piece.

HTH,


Justin.

[markharrison]

HomerJ,

Bubbles are typically caused by stirring bubbles into the varnish (it doesn't actually need much if any stirring) and overfilling the brush and then having to scrape the excess back into the can.

Those two points alone will reduce most problems. There may be other problems though as alluded to by the other respondents here.

Another thing to try is a foam brush though if you have a lot to do they are a bit of a pain.