We are working on an 1887 Pullman and are trying to save as much of the mahogany window frames as possible. As part of this process some windows will need to be disassembled. The challenge is they seem to glues together at the joints. They all have a real tight mortis and tenon joint, but we need a way to remove or dissolve the glue. My lead volunteer on this thinks it might be hide glue, and that warm water is the usual trick but that has not worked.

Anybody have a sure fire way to dissolve the glue?

Warm water can work, but since it didn’t, try a low-temp heat gun or hair dryer, being careful not to damage any nearby glass. It’s what we do to reset heads on old persimmon golf clubs. With the heat right now, you might be able to set the pieces in the sunlight for a while and take advantage of the even warmth. I wouldn’t use a lot of anything, be it water, hot air or force.

With modern glues I might suggest Un-Du, a liquid adhesive remover often found in craft stores, but it’s unlikely to work on older glues or heat-set epoxies. (Still handy for removing duct tape, unwanted decals etc., with its unique feature of being able to get stickers and such off without damaging either the object or the sticker.) It’s not liable to harm the mahogany, so if nothing else works that might.

If nothing else, you may be able to take the glass out of the frames, then have a very patient soul sit and very gently bend the frame back and forth, not enough to make any alarming noises but enough to finish cracking the adhesive if it’s already headed that way. This is one time it’s actually useful to have arthritic hands, because that reduces the temptation to just haul away on it. Slow is the way to go.

Old windows with mortise and tenon joints were also pegged in each corner to keep the frame tight. Typically, the original windows didn't need glue as they were held tight with the method of pinning which was when originally assembled the tenon was slightly offset in the mortise when the holes were drilled so when the pins were driven in the parts were tightly drawn together. Using water will swell the wood making the joint tighter.

Fred Heilich

Interesting! Can these pins be drilled out, carefully?

Yes the wooden pegs can be drilled out. I haven't been able to download several different window photos showing mortised corners. One is a Pullman clerestory window that I can't determine the method with the finish, the second is the bottom rail from an 1889 J&S coach showing the tenon, and the third is a window dash from the DL&W Greendell station that has brads in the corners. Msg me at fheilich@msn.co and I'll send them.
Fred Heilich

True hide glue made from rabbit hides is soluble in vinegar. Cleaning vinegar, 30% acetic acid is available in most hardware stores. Do not soak the wood overly long. Neutralize with baking soda. Test on a sample, for example a joint that has already been disassembled.

Thank you. I didn’t know about the vinegar.

This may be a good place to mention craft syringes. Most big-box stores have them in the paint and glue aisle. Rather than metal needles, they have larger-gauge plastic tips, straight or curved, meant for precise placement in tasks like this or for deep application of glue with less leak and smear. Also, easy-remove painter’s tape will protect the wood surrounding the joint.

I use one of these bbq marinade syringes https://www.bunnings.com.au/char-griller-50ml-bbq-marinade-injector_p0122532 modified to take a needle made from the empty inner tube of a ball point pen.

Jeff,
Can you tell me more about this car you're restoring?
I've been working on a 1901-vintage Australian Pullman sleeper for 21 years and it's of the circa-1887 design.