No Mess Glue-ups

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By Jeff Jewitt

Every woodworker experiences the trauma of discovering an errant glue splotch on their project when they apply a finish. Over the years I've experienced many glue mishaps and tried every trick out there.

Problems with errant glue can be grouped under three headings: avoiding glue squeeze-out in the first place; planning for squeezeout; and removing glue when it does squeeze out. Woodworkers have access to all sorts of modern and traditional adhesives, but for the purpose of this article I'll deal with the most common glue, polyvinyl acetate (PVA) , also known as aliphatic resin, which comes in white and yellow forms.

I do all of my gluing on a 4-fr. by 8-ft. melamine table that's about mid-thigh height and on casters. For convenience I put a few shelves underneath the table to store clamps. The slick melamine allows furniture to slide pretty easily as I'm pivoting and turning it during assembly, and it's easy to wipe up errant drips of glue. A good alternative surface material is tempered Masonite.

Before every glue-up, it's important to complete a dry run of the clamping  procedure. The dry run allows you to double-check that all of the joints are correctly machined and to get all of the clamps that you'll need within easy reach. The other thing to do is fill a container with distilled water and place it nearby with rags. Keep your hands clean during gluing, and wipe them immediately with water and a clean rag if you get glue on them.

Tricks to eliminate squeeze-out

With practice you can eliminate glue squeeze-out and still achieve full-strength
joints. Two of the best ways to avoid glue are to alter the design of the joint and to apply just enough glue to form a strong bond but not so much that you get
excessive squeeze-out.

Bevel the tenon. Use a chisel, a shoulder plane, or even a coarse file to bevel the end of the tenon, which leaves additional space inside the joint for excess
glue.

With mortise-and-tenons, both of these techniques come into play. The key is
to keep the glue from coming out of the mortise when you clamp the joint. Cut
the mortise 1/8-in. deeper than the length of the tenon, and bevel the edge of the mortise and the end of the tenon on all four sides with a chisel. This gives more room for excess glue to hide in.

Bevel the edges. Bevel the edges of the mortise with a chisel to leave an area for any excess glue to hide in.

Apply glue to the mortise walls and the tenon, keeping the glue at least 1/2-in. away from the shoulders. As the two sections are brought together, the excess glue is pushed up the tenon, but the bevel prevents it from riding up onto the mortise and instead rolls it over the glue-free section of the tenon.

  

Apply glue only to the bottom of the tenon. Leave 1/2-in. below the shoulders glue-free. As the tenon slides into the mortise, the glue is spread along the tenon by the walls of the mortise.

Ways to contain squeeze-out

Another approach is to accept glue squeeze-out but to employ strategies that
make removing it easier.

Tape off the wood-With dadoes and sliding dovetails like those often found in chests of drawers and bookcases, I dry-assemble the piece and tape off around
the joints with blue painter's masking tape, which can be removed cleanly with no residue. Apply the glue and assemble the piece in the normal way. When the glue has dried, peel away the tape, removing any residual glue. This doesn't require a lot

  

Containing squeeze-out. Prior to assembly, apply blue masking tape to visible areas of a joint where squeeze-out may occur. During assembly, any squeeze-out  goes onto the tape.

Apply finish before glue-up-With any workpiece you always have the option of prefinishing, but it's my favorite technique for multislatted pieces or where there are a lot of complicated areas to finish. Cover tenons with blue masking tape and stuff paper-towel pieces into the mortises. Stain the piece, if applicable, and apply a couple of coats of finish. Don't apply a final coat of finish, as the surfaces may get slightly marred during assembly. Make sure you use clamps with protective faces so that you don't mar the piece. If your clamps have metal faces, use squares of HomaSote (an insulation material sold at builder's merchants) to protect the workpiece.

  

Apply finish before glue-up. Mask off areas that will receive glue. Tenons are wrapped in tape, while mortises are stuffed with paper towels.

Removing squeeze-out
Sometimes glue squeezes out no matter what precautions you take. On a prefinished surface, most glue squeeze-out can be scrubbed off with a toothbrush and water, and the surface wiped clean with a damp cloth. If you miss some of the glue, perhaps because it is under a clamp, let it dry for a few hours, at which point you can practically peel the glue off the finished areas with a chisel.

  

When all else fails. If you get squeeze-out on open-pored wood, use a toothbrush to remove glue from the pores rather than a cloth, which forces glue
into the pores. To avoid staining tannin-rich woods like oak, use
distilled water.

But if you get glue squeeze-out on bare wood, you have the options of letting it
dry or semicure, or wiping it off immediately with water. In most cases I prefer to
clean off the squeeze-out before it dries. Dried glue can be a horror to remove.

Rather than grabbing any old wet rag to remove glue, I take a more systematic approach: First, use distilled water, as tap water may contain dissolved iron salts that will cause little gray spots on tannin-rich woods like oak. Use a toothbrush to remove the glue, scrubbing with plenty of water. On open-pored woods, this method removes the glue that's inside the pores. Then, with a clean cloth dampened with distilled water, wipe the joint clean.

Glue scraper. On large panels, let the glue dry six to 12 hours and then use a cabinet scraper to remove the surplus glue. Waiting longer increases the chances of tearing out the wood.

Because large panels are usually flattened using a drum or belt sander, don't
bother to thoroughly clean off the beads of glue; let them dry six to 12 hours before scraping. If you wait any longer, the beads get too hard, and you risk pulling off hunks of wood as you scrape.

This article originally appeared in the September/ October 2003 issue of Fine Woodworking