A few questions about hide glue

[spongebrain]

When making a mortise and tenon joint, it's good to make sure you account for the wood swelling from the glue right. If your joint is too tight, it will crack the wood.

But hide glue doesn't cause the wood to swell, or does it? Should a mortis and tenon joint using hide glue be slightly tighter than if you used PVA glue?

And hide glue is not a gap filling glue?

[spongebrain]

Well, I went ahead and emailed titebond my questions about their liquid hide glue.


Creep is not a design concern for chairs since they are not subjected to
sustained structural loading (such as a laminated beam in a building
carrying several tons). Liquid Hide Glue is well suited to this
application and requires the same design considerations as a PVA
adhesive such as Titebond Original. A good mortise and tenon should
have no more than 1/64" of play total in each direction. Snug fitting
joinery is desirable for adhesives and will not result in cracking;
rather it will produce stronger joints. Acetone surface preparation
will never harm a glue joint but is most necessary when working with
oily species of wood.


Hugh D. Evans
Technical Specialist

Franklin International
2020 Bruck St
Columbus, OH 43207
[email protected]

[Woodwould]

When making a mortise and tenon joint, it's good to make sure you account for the wood swelling from the glue right. If your joint is too tight, it will crack the wood.

But hide glue doesn't cause the wood to swell, or does it? Should a mortis and tenon joint using hide glue be slightly tighter than if you used PVA glue?

And hide glue is not a gap filling glue?

I've never heard of "allowing for wood swelling from the glue" when making mortice and tennon joints (or any joint for that matter). There's not sufficient moisture/glue in a joint to make any lasting effect on the wood. I make mortice and tennon joints so they are fractionally too tight to assemble by hand, requiring knocking together with light taps with a mallet.

Hide/bone glue and PVA are both water-based.

Hide/bone glue is gap filling, but it's bad practice to rely upon glue to make up for poor joinery.

[spongebrain]

Would you prefer to take apart a glued joint using warm water or shellac? What's the method exactly? Should I just pour some warm water into the cracks and let is soak in?

[toolbagsPLUS]

Would you prefer to take apart a glued joint using warm water or shellac? What's the method exactly? Should I just pour some warm water into the cracks and let is soak in?

I use a heat gun (sparingly, so you don't damage the surrounding timber) or if the joint is really old and the glue has crystallized then gently worrying it generally loosens the seal and the item then can be pulled apart easily. Light tapping with a mallet over a block also does the trick.

Never heard of metho melting the glue though? I'll try it when I get to the workshop today.

Cheers

Steve

[spongebrain]

Sorry, I meant to say denaturated alcohol, not shellac. The other question I had on my mind, was wether or not you have to worry about the alcohol in the shellac mix damaging your hide glue joints? I do realize thought that people have been using hide glue and shellac for hundreds of years, so I thought maybe it was a dumb question.

I cut the lower rear cross piece for a chair I'm making too short, and didn't notice until glue up, in a panic I just clamped it in bending the two sides. I'm used to PVA glue where this would have been a disaster. The next morning I just cut in half, poured some hot water into the mortis and tenon, wiggled the two halves out, cut a new one, with shorter tenons so I could flex the legs enough to get it to fit. Turned out to be a pretty simple fix, and only took about 15 min.

Thanks for your replies.

Cheers

[Woodwould]

Sorry, I meant to say denaturated alcohol, not shellac.
We knew what you meant.


The other question I had on my mind, was wether or not you have to worry about the alcohol in the shellac mix damaging your hide glue joints?
Alcohol will not dissolve animal glue (the minute percentage of water in the alcohol would, but not that you'd notice).

Alcohol can be used in the course of restoration to help break down animal glue into smaller grains when it is already very old, dried out and friable. The glue appears as sand-like granules and is not made sticky by the alcohol or rejuvenated in any way.