Glue Interfering with Door Finish
A discussion about dealing with glue near raised-panel cabinet door joints that stops the wood from taking an even finish. January 14, 2008
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Question
I made a bunch of raised panel doors. On some of the doors, some of the glue has showed up in the finish around the joints for the raised panel. What I don't get is that I didn't wipe off any glue. And I planed the panel down by almost 1/4" after I glued it up. I don't get how the glue is showing up.
Forum Responses
(Finishing Forum)
From contributor P:
Did you rip one side on the table saw? Sometimes the edge of a ripped board won't be perfect and the joints have little gaps that will show up as you thickness.
From the original questioner:
I joined them. Most of the glue that shows up in the finish isn't really on the joint, but around the joint, which is really strange. This is soft maple.
From contributor D:
After glue up but before finishing, inspect surfaces under a black light. The black light will show you where you have glue. This won't help you now, only subsequent to now.
From the original questioner:
Also, it's almost like the glue is bleaching the maple around the joint, so when you stain it, the area around the glue joint is lighter than the rest of the panel. How can that be?
From contributor R:
I doubt if a bleaching action is taking place. What kind of glue are you using? Is it possible that during your planing operation, the glue from the joints is being heated up and moved across the sides of the joint and saturating the wood, thus preventing the stain from taking in those areas?
From the original questioner:
I'm using Titebond II. You know, that actually makes sense. Maybe I should try a poly glue or epoxy resin. Never really tried either for raised panels.
From contributor T:
PVA glues soak into the wood on each side of a joint. The larger and more open the pores are, the farther it soaks in. The more clamping pressure you put on the joint, the farther it soaks in. When you plane off the top of the joint, you're exposing the areas on each side of the joint where the glue has penetrated and that area is sealed - it won't take a penetrating stain. I think you've proved it. PVA glue will melt, but I doubt that planing would generate enough heat to melt it enough to cause it to migrate. If it did, I'd expect your panel to come apart when you planed it.
From the original questioner:
Thanks - that's really interesting. I never knew that. What glue what you recommend?
From contributor J:
I bought a light bulb sold as a black light. Overhead lights on or off, I can't see any glue! Need further advice, probably something obvious...
From contributor R:
Bulbs are too low in watts. You need a 60 watt stick UV (black light) and near complete darkness to see whatever you are looking for. I usually just throw a furniture pad over myself and the piece like a tent in order to inspect with the black light.
Glues will fluoresce white to bluish green depending on type. Shellac (fresh up to 50-60 years) will fluoresce orange, unless they have had a lot of UV exposure where they will then fluoresce more green like NC lacquers, varnish, etc. do.
From contributor K:
There is also an additive that you can add to glue to make it show up better under black light. It's available premixed.
From contributor T:
I use Titebond original for almost everything. It stays more flexible than Titebond II and I rarely need water resistance. But it does the same thing as most adhesives that I know of will.
The easiest way to solve your problem is to make the first step in your finishing schedule a wash coat, especially if the wood contains larger, open grain pores.
