I have several chairs to reglue and since they were originally glued with hide glue, I thought I’d wade right in and get started with the real thing. So far I’m liking what I see.
For joinery – chair joints, mortise and tenons, and edge gluing boards… what is the clamp time and what is the time for full setting? I’ve heard 3-4 hours is all you need for hot hide glue, is this true?
Replies
Chap down the street has used hide glues for years on antique repairs. His rule of thumb is to leave clamped for 4-6 hours, then unclamp (in case there is stress in the joint) and allow to harden overnight. I've followed that practice on new furniture with no problem.
As a side note, I've tried rub joints for edge gluing of two boards and wasn't as happy as edge joints I clamped for several hours. The former had thicker glue line than the clamped joints, which isn't really a surprise. Hide glue I read is the only glue with internal adhesion, so that the two surfaces are pulled closer together as the glue cures, which is why fub joints work with it. Okay for reinforcing glue blocks, but I think clamping would be preferred for all else. Just my two cents.
When the glue fully cools I remove clamps. Usually 20 minutes or less. I sometimes do not bother with clamps, might use pinch dogs or just hold the parts togeher for a few minutes. Depends on the glueup, small parts i generally hold together.
I have glued up boards and run them thru the planer an hour later.
mike
Kent,
While hot hide glue allows rubbed type joints, clamping the joint always results in the thinnest glue line and, and probably a stronger joint. Although, many times a rubbed type joint, if stressed to the point of breaking after fully cured (at last days) will NOT break at the joint line, but will fracture wood fibers on either side of the joint. This shows the glue joint is stronger than the wood even without clamping.
I don't think there is any need to clamp a hide glue joint longer than about 30 minutes. In that time, the glue has fully cooled and has no ability to creep or move. BUT I would never work with the piece for at LEAST a day, even longer. Leaving the clamps on doesn't improve the strength, but it prevents you from attempting to finish too soon. Even though the clue has set, it will gain hardness and the surrounding wood needs time to distribute the moisture it has absorbed from the glue. The wood is swollen with that moisture. Any attempt to plane or sand it will remove the swollen tissue. Then when the fibers fully dry, the glue line and some surrounding wood (on either side of the line) will be shrunken below the plane of the rest of the surface.
Rich
Great point about the moisture and expanded wood, Rich.
Some great advice from you all. Thanks. I think I'm going to like this stuff!
"BUT I would never work with the piece for at LEAST a day, even longer." Amen. Something I don't remember being mentioned specifically in the posts, but is my understanding of how hot hide glue behaves is that it kind-of "gels" not long after being applied, so the joint will feel firm, but the glue hasn't actually cured yet. This would be "gaining hardness", right?forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Kent,
I rarely clamp a hot hide glue joint. Usually if clamping is called for the very short open time of unaltered hot hide glue, makes it difficult to do anything but the simplest of assembly before it's too late. The addition of urea gives one enough time to clamp more complicated assemblies. With the depressed hide glue, I allow the clamps to stay on at least 6 hours and preferably over night. That may be overkill, but longer won't hurt anything.
Rob Millard
http://www.americanfederalperiod.com
This forum post is now archived. Commenting has been disabled