What to do with glue squeeze-out - when should we remove it?
Ask three or more woodworkers the above question and you'll probably get three different answer: right away, after a few minutes and after the glue had dried. Chances are equally good that the person who gives you any of the three answers will have a rationale that seems plausible. In short, the subject of glue squeeze-out is one that's sure to generate some good discussion among anyone who has worked with wood.
Whenever you clamp two pieces of wood together with glue in between, you're dealing with variables in clamping pressure, consistency and amount of glue and species of wood. All of these factors can affect the amount of adhesive that may ooze out of the joint, as well as the technique you use to remove it.
Some Squeeze-out is Good
A little glue squeeze-out — a few tiny droplets or dribbles along the joint — is a sign of a good glue application job. No squeeze-out means you might have applied too little glue, creating a "starved", potentially weak joint. All the experts agree on this point.
Glue squeeze-out becomes a problem only if you can't com¬pletely remove all the excess glue from the wood surface. Any glue that remains on or in the wood fibers can hamper application of finishing material. You know you must remove all the glue that gets squeezed out from the joint, but when and how?
Generally, we don't advise waiting until the glue has dried hard. Note the "generally." Sometimes, you might be able to estimate your glue needs exactly and get just a few tiny beads of glue squeeze-out. If you have no more than this, you can wait till the glue has dried and flick off the beads with any sharp tool.
But, as was mentioned earlier, you could be making a serious mistake in trying to limit glue squeeze-out to so small an amount. Remember the starved joint.
The other extreme is no better. If so much glue oozes out that you'd need a chisel or lots of sand¬paper to remove it after it hardened, you're in trouble. Since the completely dry glue is quite likely harder than the grain of the surrounding wood, the adhesive you cut away might take some wood along with it. And if you use a sander, you risk sanding away too much of the wood.
No Water Is Better
We agree to disagree somewhat with both Snider and Duncan regarding use of a damp sponge or rag. We're convinced that the combination of moisture and pressure can indeed push some glue into the pores of the wood. Sanding will remove the glue at the surface, but perhaps not all the glue that was forced down deep. Why take a chance and wait maybe a couple of days for the wood to reach an equilibrium state before you can sand off the residue?
Let Glue Gel
Clean up excess glue after it has gelled a bit but before it has hardened. Follow Snider's advice and wait 5 to 10 minutes (or longer) after clamping. At this point you'll be able to slice away the "cottage cheese" with a dull chisel or other type of scraper.
Scraping the glue off after it has set for a few minutes makes sense. It's sort of a compromise between removing it right away and waiting until it's completely dry. Of course, once you remove the skin that's formed on the surface of the glue, the glue underneath is still wet. But removing it at this point keeps you from smearing the glue all over quite as much. And by removing as much as you can in this way, you minimize the sanding you'll have to do once the remaining glue has hardened.
How To Avoid Excessive Squeeze-Out
• Check that joint parts fit well by clamping together before gluing. Open pores of wood by sanding.
• Use a brush about the same width as the wood to spread glue. Glue directly from a squeeze bottle should be applied in zig-zag lines to both surfaces, then the pieces rubbed together to distribute.
• It's best to apply glue to both surfaces thinly and allow to par¬tially set before joining pieces.
• Check drying or "set" time of glue you're using. Some set up faster than others. Work to the pace of the glue.
• Don't apply too much clamp pressure. The object is to create a thin film of glue between parts. Too much pressure will squeeze the glue out, resulting in a starved joint. Usually, finger tight will do.
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