using polyester to seal porus wood


Senior Member
Is there any tip when mixing polyester? I got a bottle of pure unsaturated polyester resin, with a small bottle of MEKP to cure it. I plan to brush this onto an ash body to seal the grain so to make grainfilling a little painless. However I tried to mix small amounts to see how this stuff react and it would always cure with a sticky film over the top. Is this because of poor mixing or not enough hardener? The bottle says I should be mixing 1-2% by volume (so thats one drop of MEKP for 10cc of resin, assuming that one drop is .1ml).

Am I better off using Stewmac colortone grainfiller than unsaturated poly resin? I chose poly because it sands much easier compared to epoxy...
Polyester? Thats a plastic isn't it?
I guess I'm out of the loop on finnishes, never heard of a polyester wood finnish,  I will check this out, I always like laquer, because it dries hard and sands well.

Can't wait till the Brains of this outfit chime in here :laughing7:

Well, I just googled polyester finish and there it is, Looks to be very impressive , can be buffed like 8 hours after applying

The guy says, most people dont apply enough, apply it till you think its gonna run, then add 2 more coats  :hello2:

Somewhere it says that it can be applied as thick as 40 mils, thats thick.

I can't wait to see your progress and the finnished product. 

One drop = .06 ml, so your filler probably isn't completely drying out properly as you're not using enough hardner per the 1-2% formula you gave.

As to slathering this stuff on 40 mils (1mm) thick; while the product may contain that in it's info/directions, I think that refers to applications like furniture refinishing, rather than guitar/musical instrument applications.

I was doing some research on the polyurethane vs. nitrocellulose finish "contraversy" a while back, but the only real empirical data I could find seemed to indicate that the amount/thickness of the finish applied  had a lot more to do with potentially "deadening" the resonance of the wood than the type of finish used....
I only plan to use this to fill ash, not as a finish of any kind. Therefore its just a thin enough layer to fill the grain, then its lacquer on top...
Then why not use a laquer based filler?  I would experiment on scrap wood first.

I would think that you can seal the wood pretty easy with a good shaker can.

because I cannot get oil or lacquer based wood filler, if I could I wouldn't be asking this. You can't use lacquer like sanding sealer or clear to fill grain because lacquer will shrink forever and the grain will pop back up a month or so from now. I like to use polyester because it does not shrink once dried.