Help and guidence

[richard b miller]

woodworkers- i built an outside potting bench for my wife. it is all made from 2" pine. the top i cut into 3" strips then glued them back together with titebond 3 glue. i stained the wood and coated it twice with GF 450 exterior varnish last week. the top was smooth. on monday, i put the bench on the back porch and yesterday we got ~1/2" of rain. most of the places where i glued the top together raised a little. the bottom side of the top was still bare wood.
did the top raise because of the unfinished bottom? when the top dries out, will the raised joints settle or must i sand them down?

thanks all
rich
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[Matt Day]

Just to be clear, there is unfinished pine in an outside environment right? If so you've got an unbalanced panel - moisture cannot penetrate the top of the panel but it can on the bottom, which causes cupping which is what you're seeing.

I'd pull off the top and let it reacclinate and dry out, then deal with it. You'll likely need to strip the finish with sanding or planing and reflatten it. Or just make a new one and seal both sides this time.

[Don Bullock]

Fully agree with Mat. A bench like that will most likely have to be refinishd every year.

[Doug Hepler]

I agree with Matt's first paragraph. But you can give the underside of the top a chance to dry out before you remove the top and refinish it. You might encourage the process by exposing the underside to sunlight or a heat lamp. If you get it flat again, apply as many coats of finish to the underside as you did to the top.

Doug.

[Andrew Hughes]

I think Richard might be taking about his glue lines.He mentions using Titebond 3 so it sound like glue creep.

[Wayne Lomman]

Sounds like glue creep to me as well. Let it dry out inside for a few days and then seal any bare timber. If the glue lines are not acceptable, lightly sand them flat with say 320 paper and recoat.

However, don't pull the top off to let it dry. It is nicely held straight as it is and it will dry straight if you leave it in place. Cheers

[richard b miller]

thanks all! pulled the top off and let it dry for a few days. its almost back to normal but i will have to
lightly sand down some of the joints and refinish.

But someone please explain glue creep. there's no glue coming out of the joints.

[Doug Hepler]

Richard,

As I understand glue creep, its the ability of a joint to move under stress before the adhesive has fully cured. PVA adhesives like Titebond remain flexible for some time after they appear to have dried. This depends on the adhesive formulation and the temperature. I think glue creep occurs when a (poorly made) joint is forced to close and then released from clamps before the adhesive has fully set. A related idea is that the water in PVA is absorbed into the adjacent faces of a joint, causing them to swell slightly. Then the wood dries. If the faces of the joint were leveled when the wood was swollen, the joint may show as a slight depression after the wood has dried.

I do not think, from your description, that you had glue creep. As I posted earlier, your panel warped because one side absorbed more water and swelled slightly. You seem to be on the way to resolving the problem.

Edit: My understanding of this term does not seem to be the only one. For another view of glue creep see this link.

Doug

[Mel Fulks]

I don't think even the best varnishes protect pine well on a horizontal surface. I don't think the glue is the problem. My aproach would be : keep it covered during rain, keep it sloped during rain, or glue canvas to the top then paint it.