Hopefully this will read like a mystery and entertain you!
I am restoring a 3-leg table. The legs are mortise & tenon. Two of the legs were loose and had been re-glued before I saw it. The glue was reddish and crystalline. PICTURES 1 & 2 show the tenon and mortise after I used a rubber mallet to free the joints.
I planed and chiseled to get rid of most of the glue surface on the shoulder area of both mortise and tenon, the tenon cheeks and ends, and the mortise interior, including the bottom. I did not go down to raw wood on the tenon cheeks or hog out the mortises because I didn’t want to make the joints loose.
PROBLEM 1 – One joint is still snug but the other one is loose (a shim from a 3×5 card makes it snug). PICTURE 3 shows the tenon after I cleaned it up.
PROBLEM 2 – The shoulders all have gaps, including the original, still attached joint. The original has a reddish glue filling the gap, looking like it is very neatly caulked. PICTURE 4 shows the original joint and the gap at the shoulder of a cleaned up leg. The tenon shoulders are not curved and it is beyond my capability to do concave tenon shoulders. The mortise lip is pretty flat but I don’t want to work beyond the immediate shoulder area because I don’t want to refinish.
QUESTIONS –
1) What type of glue should I use? The surfaces are not bare wood to bare wood and I need some squeeze-out at the shoulders to fill gaps. Gorilla Glue?
2) Should I shim the slightly loose tenon? If so, with what? (card stock? glued plane shavings?)
3) What else am I missing? (I am always amazed at how little I know!)
Replies
Gdh,
1) What type of glue should I use? The surfaces are not bare wood to bare wood and I need some squeeze-out at the shoulders to fill gaps. Gorilla Glue?
Hot hide glue. The modern glue from the repairs ought to be removed, as you are doing. Hot water may help soften what looks to be white glue. Avoid modern glues, such as Elmer's, Gorilla or epoxy, if at all possible. It is preferable to use hide glue on repairs of an antique, as it is compatible with the old glue (same material) as well as reversible (water soluble) if further repairs, or an alternative course of treatment, are needed in future.
The red crystalline stuff that the gaps are "caulked" with looks like stick shellac. Once the joints are cleaned of all repair gunk, something similar may not be needed, if you pull the joints up tightly. Clamping a tripod table leg to the shaft usually requires that you saw out a conforming block that may be itself clamped to the leg. This block will have a notch cut in it to accomodate a clamp so that pressure is applied directly in line with the center of the joint. Be sure to pad the block so that it does not bruise the curved edge of the leg, and put a pad between the clamp and the shaft, too. Do a dry run, so that you can be sure of putting pressure where it is needed to pull the joint closed. Clamp one leg at a time, and let it dry before doing another.
2) Should I shim the slightly loose tenon? If so, with what? (card stock? glued plane shavings?)
You can use card stock, or cotton, linen fabric to take up slack in loose joints; better is to glue a slip of veneer onto the tenon, and adjust the fit with a rabbet or shoulder plane, rasp, or whatever you are comfortable using. You may want to add to one or the other, or both cheeks of the tenon, to obtain a good fit within the mortise, and keep the leg centered on the shaft.
3) What else am I missing? (I am always amazed at how little I know!)
If gaps remain after glue up, you can fill them with stick shellac as before, or (easier) one of the colored wax crayon type fillers. Either way there will be no strength added to the joint, it's purely cosmetic. Hide glue is a reasonably good gap filler, not for strength so much, but it is a neutral color, and can be itself colored with magic-marker type touch-up pens if needed. Be sure and wipe off excess dribbles with a wet rag, or dried glue can be easily peeled off finished surfaces, or re-dissolved with a warm water soaked rag or paper towel, and a little rubbing. Dry the finish surface immediately after wiping.
Ray
Ray said about all the good stuff and I agree.. I will leave it at that!
Definitely use hide glue.
You might also want to check and see if the tenons are bottoming out in the mortise after the years of shrinking causing the gaps, it's possible (but I doubt it).
I would glue a shim of veneer on, and use a different species so the repair is obvious to anyone who may have to fix it in 50 years.
I personally wouldn't worry about the gaps. It's an old piece and that's what happens. And they don't look to bad to me.
But if you really want to remove them, I would pare away a little of the inside shoulder, that should snug them up a bit.
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