Painting air-dried pine

[Andrew Smith (Canada)]

Hello

I built a picket fence this year. The pickets were cut from air-dried pine sold as "board-and-batten", for siding.

The wood sat in my basement workshop over the winter after I milled it but before I put the finish on.

I rolled on a coat of primer or two (Zinsser bulls eye exterior primer), and sprayed on the stuff home depot calls "deck stain". I don't actually know what that is, the can has no technical details on it. It's waterbased and quite thin but it doesn't feel like any stain I used in the past. I'd rather call that thin paint than stain.

Anyway, from the start I had problems with bleeding through the finish. That's why I put two coats of primer on.

I'm guessing that's the sap from the pine that has not dried up because it never went into a kiln.

This is what it looks like:

bleeding.jpg

I won't be doing anything for this fence, but I really like working with this wood. It's exceptionally cheap, and looks pretty good once milled.

For the future, is there anything I can do to prevent that bleeding?

I've heard recently that shellac works great as a sealer and it sticks to anything, which sounds to me like it would make a great (though expensive) primer.

Or else, if I chose to put spar urethane on as a finish - would that work fine or would it have a hard time sticking to this stuff that's bleeding through?

[John TenEyck]

Shellac is a great spot primer over knots. BIN pigmented white shellac primer would be an even better choice for stuff that will be painted; again, only as a spot primer for exterior work. You can then apply an exterior primer over the whole thing after the knots are spot primed.

I would not use stain over primer; stain is meant to be used on bare wood or wood that has been stained before, not over sealed wood. If you want those knots to disappear you should spot prime them with one of the shellac based products discussed above or another stain blocking primer, then prime everything with an exterior primer, then paint them.

John

[Edward Dyas]

Hello

I built a picket fence this year. The pickets were cut from air-dried pine sold as "board-and-batten", for siding.

The wood sat in my basement workshop over the winter after I milled it but before I put the finish on.

I rolled on a coat of primer or two (Zinsser bulls eye exterior primer), and sprayed on the stuff home depot calls "deck stain". I don't actually know what that is, the can has no technical details on it. It's waterbased and quite thin but it doesn't feel like any stain I used in the past. I'd rather call that thin paint than stain.

Anyway, from the start I had problems with bleeding through the finish. That's why I put two coats of primer on.

I'm guessing that's the sap from the pine that has not dried up because it never went into a kiln.

This is what it looks like:

bleeding.jpg

I won't be doing anything for this fence, but I really like working with this wood. It's exceptionally cheap, and looks pretty good once milled.

For the future, is there anything I can do to prevent that bleeding?

I've heard recently that shellac works great as a sealer and it sticks to anything, which sounds to me like it would make a great (though expensive) primer.

Or else, if I chose to put spar urethane on as a finish - would that work fine or would it have a hard time sticking to this stuff that's bleeding through?

By using the shellac based primer I think you did about all you can do to prevent bleed through. only thing I can suggest is spot prime the spots again and touch up the finish. The shellac based primer will do more to block the sap bleeding than a spar urethane would and you probably would have difficulty getting the stain to adhere to the urethane.

The stain was probably a solid color stain is why it looks like paint. I agree it's more paint than stain.