How To Paint Over Wood With Polyurethane

Ricki · 02-20-2012, 11:31 PM

I have a stair rail that has a thick coat of polyurethane. I would like to paint it. Do I need to sand it off? Can I just use primer?

joecaption · 02-20-2012, 11:43 PM

Hand railing get a lot of abuse so paints not likly to stay stuck for long.
But if your still going to do it it would be best to sand it to get it all off, use bonding a primer then enamel paint.
No enamel paint does not have to be oil based. It's just a lot tougher paint.

Someone going to suggest a deglosser but I would be afraid to use it because it's powerful stuff and could drip on to the treads below, also with a hand rail your going to need the give the rail some tooth for the paint to have something to hang onto.

jsheridan · 02-21-2012, 06:08 AM

Ricki, welcome. You don't need to remove the poly. I would get some 150 grit sandpaper, and give it a good sanding. Wipe it down with a damp rag to remove the sanding dust. Then apply a bonding primer like Zinsser 123, which you can get a quart of at Home Depot. Then apply two coats of whatever trim enamel you are using on the rest of the trim in your house. It's best to use at least a semi-gloss, especially if it gets a lot of handling. Lower gloss might be more difficult to keep clean. If you prep right and use quality products, the handrail will stay looking nice and be sound for a long, long time. Good luck and stop back with any further questions.
Joe

sdsester · 02-21-2012, 06:16 AM

Why not use a white polyurethane or even a melamine product? I would not use regular latex enamel over poly on a railing. Only drawbacks to melamine are that it is brittle and chips; and it is somewhat challenging to apply.

You should have no trouble finding white poly at an industrial paint supplier. Or better yet, a marine supplier should have it in quarts. It is a little pricey. A bright white, high gloss, porch and floor product would work to for a railing also. Just have to think outside the box to find what you need.

For example this is a brand I used restoring sailboats ages ago.

http://www.iboats.com/Mega-Gloss-tra...view_id.363304

I do think you should scruff up the existing surface a bit to improve adhesion. I would not use a liquid de-glosser. Good old fine grit sandpaper should do the trick.

Brushjockey · 02-21-2012, 07:23 AM

Painting over varnish happens all the time, but needs to be done right.
As sds is saying - its all about adhesion. Sand to dull the shine all over, this gives the primer something to grip to. Then wipe off dust and prime with a very good high adhesion primer. Here are some examples: Glidden Gripper, Insul-x Stix, Zinsser 123 and Smart Prime, Ben Moore Fresh Start, SW bonding primer, etc. This is the most important part- the first thing to hit the varnish.
Then finish with a high quality finish - after all that you don't want to use crap paint do you!

jsheridan · 02-21-2012, 05:26 PM

I neglected to mention it might be a good idea to use some form of detergent/rinse prior to sanding. Handrails tend to collect a bit of oils/grease/dirt from hands. That hit me out of the blue today while driving. Wasn't thinking about it, just popped into my head.

chrisn · 02-21-2012, 05:38 PM

If it were mine. I would prep as stated and use a quality oil based semi gloss( if you can get it)

sdsester · 02-21-2012, 08:05 PM

Quote:

Originally Posted by chrisn

If it were mine. I would prep as stated and use a quality oil based semi gloss( if you can get it)

One reason I mentioned a marine finish. For some reason, some states seem not to have banned oil products for marine use. OP may be able to get an oil based poly at a marine store but not at the paint store across the street. Go figure!