Hot Hide Glue Question

[Mike Henderson]

I had a woman bring me a table a few days ago. It looks somewhat like the picture I've included here, but it has two drop down sides. An arm swings out from the leg frame to support each side. The legs splay out as in the picture.

Anyway, her problem was that the boards were coming apart - the glue was just giving up. When I disassembled the table, indeed many of the joints between boards in the table top and sides were just loose - the glue was there but it had deteriorated basically to dust. It was hide glue.

The table was not valuable but it was something she wanted to continue to use and to pass on to her children.

I ran each side of each joint through my jointer and glued it up with PVA. The top and sides are now strong and should last a long while.

But back to hide glue. Suppose I wanted to release two boards where the hide glue had not deteriorated to the point of dust - how would I get the hide glue to release? I really wouldn't want to put a lot of water into the wood and heat could destroy the finish on the table top. Is it possible to get two boards glued together like this apart?

Mike

table.jpg

[Jim Koepke]

I have been reading this thread. Now I am a bit confused.

I really wouldn't want to put a lot of water into the wood and heat could destroy the finish on the table top. Is it possible to get two boards glued together like this apart?

If it were me, worried about the finish, then the last thing I would want to do is separate the boards in the table top. Wouldn't that mess with the finish as much as heat and moisture?

jtk

[Kees Heiden]

I have now completed a few projects with hot hide glue. I like the "witchcraft" of it all, the boiling soup in the cauldron, the funny smells, but also the bit of intelligence you need to get it all working out. It's not overly difficult (I'm not talking about difficult violin making here!) , just a lot more work and it calls for attention all the time. It can get a bit nervous around larger glue ups, but when you can divide the job in many small ones it isn't so bad.

For a quicky job I still prefer the glue in the bottle. And on a hide glue project, when I accidentally bust of a splinter in a corner of my work, I'll likely grab the bottle of PVA too, instead of soaking the glue pearls, boiling up the kettle, etc. Maybe I should make myself a batch of liqued hide glue, so I have something easy in reserve.

[Derek Cohen]

But back to hide glue. Suppose I wanted to release two boards where the hide glue had not deteriorated to the point of dust - how would I get the hide glue to release? I really wouldn't want to put a lot of water into the wood and heat could destroy the finish on the table top. Is it possible to get two boards glued together like this apart?

Hi Mike

A panel split in a recent frame-and-panel, and I needed to repair this before moving on with the build. Fortunately, the mortice and tenon joints were held together with liquid hide glue. I drilled out the pegs, and then steamed the joints - wet cloths and hot air gun. they came apart with a little gentle persuation. That was one of the good parts. The other was that one can use (liquid) hide glue directly over (liquid) hide glue. You cannot do this with other glues, except epoxy.

Regards from London

Derek

[Mike Henderson]

I have been reading this thread. Now I am a bit confused.




If it were me, worried about the finish, then the last thing I would want to do is separate the boards in the table top. Wouldn't that mess with the finish as much as heat and moisture?

jtk

My question was hypothetical - how would you release two boards that were glued together. But in this case, the glue had failed in most of the joints so it was reasonable to expect that the remaining one or two joints would fail within a few years.

So if I wanted to take the remaining couple of joints apart, how would I do it? The only way I can see is to cut them apart, maybe with a track saw carefully aligned along the glue line. But since they're hide glue and hide glue is suppose to be reversible, how would I get them apart without cutting them apart?

What I've heard is that you use moisture and heat to reverse hide glue. I certainly don't want to soak the wood, so that leaves heat. How would I put heat into the joint without ruining the finish?

Mike

[When I reglued the loose boards, I used cauls to flatten the joint. Even with that, the joints were not perfect, close but not perfect, but she was satisfied.]

[Mike Henderson]

But back to hide glue. Suppose I wanted to release two boards where the hide glue had not deteriorated to the point of dust - how would I get the hide glue to release? I really wouldn't want to put a lot of water into the wood and heat could destroy the finish on the table top. Is it possible to get two boards glued together like this apart?

Hi Mike

A panel split in a recent frame-and-panel, and I needed to repair this before moving on with the build. Fortunately, the mortice and tenon joints were held together with liquid hide glue. I drilled out the pegs, and then steamed the joints - wet cloths and hot air gun. they came apart with a little gentle persuasion. That was one of the good parts. The other was that one can use (liquid) hide glue directly over (liquid) hide glue. You cannot do this with other glues, except epoxy.

Regards from London

Derek

Thanks, Derek. My question was how to release a joint of two boards glued together along their length.

Also, polyurethane glue (Gorilla glue) will stick to just about anything, including hide glue and PVA (and epoxy). The disadvantage of polyurethane glue is the foaming. I use poly glue in most "difficult" repairs where I cannot get back to bare wood.

Mike

[Just as a side note, poly glue is great for repairing bubbles in veneer, no matter what glue you used to attach it in the first place. Slit the veneer, work the poly glue under the veneer, put a caul on it and clamp. Usually don't get any foaming in that situation.]

[And a usage note on poly glue: After it sits around it gets pretty thick. To thin it out, put the bottle in a pot of hot water - close to boiling temperature. The heat will thin out the glue, almost to the consistency of water. That makes it easier to work into tight joints.]

[Mike Henderson]

After the glue failure when I tried to use hot hide glue to put together a box, I re-worked all the sides, trimming them back to get to clean wood and re-glued the box with PVA - while observing the process to try to understand why I failed with the hot hide glue.

My conclusion is that my problem was the very short open time of hot hide glue. Putting even a small box together takes time - to apply the glue, to get all the pieces together and then get it into clamps. And since I was using plain miter joints, it takes some fiddling with the clamps to get all the miter joints aligned properly. During that time, the glue needs to be "open" (not set) so that the wood can be moved and adjusted.

Hot hide glue simply does not give that much open time. Most likely, the glue had started to gel while I was putting the clamps on and movement in the joint during clamping broke the glue bond.

Overall, that seems to be the major issue of hot hide glue. It's a good glue in the right situation (and the right joinery), but the very short open time is a real limitation. I've had complex glue ups where I chose an extremely slow epoxy just because it would take a very long time to get the project assembled. I understand that in our ancestors' shops a complex glue up may have involved a group of woodworkers in order to get things assembled before the glue "set" but I'm working alone and don't have that luxury.

Also, while hot hide glue is a good glue, there's nothing about it that is compelling over modern glues. Some people tout the reversibility of hide glue, but I've repaired a lot of furniture that was put together with modern glues. Another claim is that you can finish over hide glue without it showing but my experience is that it does show, very obviously, under a finish

So, overall, I'm glad I had this opportunity to experiment with hot hide glue. I'm sure I'll find opportunities to use hot hide glue in certain situations but I can well understand why our woodworking ancestors switched to modern glues when they became available. Working with hot hide glue is difficult and does not provide any significant advantages over modern glues

Mike

[russell lusthaus]

Mike

You are correct and the way I wrote that does make it seem like I was suggesting that Hide Glue is water proof or resistant. In fact, as you correctly point out, it is definitely not water proof at all and will dissolve away in water. I was clumsily listing the important properties of glue in general that the user must choose between - and its water resistance, in my opinion, is one of the best thing about the titebonds over hide glue. As to flexing - I use hide glue on the back of bows to secure raw hide and sinew - and in this location, the materials are designed to stretch with a properly working bow. As a result, I have always thought hide glue somewhat flexible in that in this use it does not crack, but I am willing to learn if I am mistaken. If mistaken, though, I would need some other explanation why it does not crack on the back of a bow?

Russ

[russell lusthaus]

. . . I know hide glue joints in furniture sometimes come undone or loosen due to the glue taking moisture from the atmosphere . . . and undoing itself . . . .

[Mike Henderson]

Mike

You are correct and the way I wrote that does make it seem like I was suggesting that Hide Glue is water proof or resistant. In fact, as you correctly point out, it is definitely not water proof at all and will dissolve away in water. I was clumsily listing the important properties of glue in general that the user must choose between - and its water resistance, in my opinion, is one of the best thing about the titebonds over hide glue. As to flexing - I use hide glue on the back of bows to secure raw hide and sinew - and in this location, the materials are designed to stretch with a properly working bow. As a result, I have always thought hide glue somewhat flexible in that in this use it does not crack, but I am willing to learn if I am mistaken. If mistaken, though, I would need some other explanation why it does not crack on the back of a bow?

Russ

You make a good point, Russ. All the older hide glue I've seen on old furniture has been pretty hard. When I've had to remove it, it chipped when I worked it with a chisel to remove it. But your example of a bow would contradict the premise that it is not flexible. And nothing is better than actual experience.

Maybe the hide glues that you use and the hide glues I've encountered had different compositions. Or maybe the fact that the glue is flexed throughout it's life on a bow makes a difference - whereas on furniture the glue is not flexed.

Like you, I am willing (and trying) to learn, also.

Mike

[Leo Passant]

Joints glued with animal glue can be dismantled using a combination of heat and moisture, but it does require some effort... they don't just fall apart in a damp atmosphere.

Animal glue can easily be made waterproof (if that's really required) and its open time can be extended to five minutes or more with the simple addition of some urea (in the past, cabinetmakers used to make up their glue with stale horse's urine instead of water). I do the vast majority of my work using three parts of glue to one of urea.

[paul cottingham]

I use hot hide glue for pretty much all of my joinery in projects. I still use PVA for quicky joinery on little projects.

Seriously, as i have said many times in the past, i am at best a hack woodworker. And i have little trouble with hide glue.

[Leo Passant]

Another issue: I was building a box so that I could work with hot hide glue. I used miter joints, as I have many times with PVA glue, and cut the miters on the Kapex (they were good miters). Glued up the box with hot hide glue. Then I cut the top off and was applying shellac on the inside of the box (I had sanded it earlier). As I was applying the shellac, I heard a "pop". Investigating, I found that one of the miters had come unglued.

I meant to respond to this comment in my last comment (#71) above, but forgot. Alcohol – as used in your shellac polish – is hygroscopic i.e. it absorbs water from its environment. If the glue you used was too thin or had voids, the polish likely seeped into the joint, sucked the moisture from the glue and the box (under some degree of tension) popped apart.

When heat and water can't be used to separate a glued joint (as when repairing valuable antique chairs), I inject pure alcohol into the joints whereupon the glue becomes anhydrous and crumbles. The chair frame can then be gently tapped apart.

Antique furniture in an overly hot/dry situation can reach a state where the glue dries out and becomes brittle and subsequently fails. This is another reason to include a certain amount of old horse urine (or urea, if you've run out) in all glue applications, as it too is hygroscopic and keeps the glue from drying out.