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I would love to hear more about your thoughts on clamping time for hot hide glue in a number of applications. I use the Behlen 164g hide glue, but have been considering picking up some 315g to try for bridges, brace regluing , cleats, etc.

Times I use or have in mind based on reading/light experience:

Braces - radiused brace gluing, I've been leaving in the go-bar deck for 8hrs+

Bridge - pre-shaped to fit top radius, minimal stress, short clamp time ok with higher strength. (I had been clamping overnight, 12+ hours with 164g)

Top/Back joining - almost no stress, short clamp time should be fine?

Top/Back gluing to rims - I've been leaving in the go-bar deck / spool clamps for 12hrs+

Woodie G talks about as fast as 6 hours to string-up with 315g hide glue on bridges - granted that was as fast as they could go, but no failure per the thread.
viewtopic.php?f=10101&t=47670&p=630517&hilit=hide+clamp+time#p630517

Robbie O'Brien has a great Tips Du Jour video in which he appears to use only a few minutes of hand force clamping with 315g hide glue for brace repair.
https://www.youtube.com/results?search_ ... +heet+glue

Have I been clamping for much longer than necessary?
Would love to hear more thoughts on functional times for clamping HHG.

When I was taking violin making lessons I was told the clamp time was two hours, period. I use an over night clamp time with any water based glue when distortion of the parts might be an issue, such as gluing up a fingerboard, to allow for the moisture to get out. When I was demoing HHG to a student I made a 'rub joint' out of a piece of leftover brace stock. I planed the surface flat, cut the piece in two, applied some 185 gram glue, and rubbed them together until the glue caught, and put the pieces down to set. About 15 minutes later I clamped one in the vice, hit the other with a hammer, and got 100% wood breakage. Maybe the long clamp times is not such a big deal. These days I tend to go with 45 minutes or so for most stuff.

+1 to Alan. Do the experiment. A large area joint like a headstock scarf joint won't be dry all the way to the center after 15 minutes, but enough of the outer edge will be dry that it's very difficult to get apart even dunking it in boiling water.

But joint strength aside, moisture expansion can be an issue. It's fine to unclamp a headplate after 2 hours, but due to the large joint area, it takes time for the water to diffuse through the wood and out to the air. If you level it right away then it will go slightly concave across the grain later.

Fingerboards are the most important place to leave for 8+ hours before doing anything, because every tiny bit of movement is bad for playability. I level the board on the guitar, so I can safely unclamp after an hour or two, but still wait before leveling. If you glue on a pre-fretted board, then keep the clamps and rigid caul on overnight to discourage movement as much as possible.

Far more important than clamping time is temperature. If the glue cools before you get it clamped, or is disturbed after it cools, the joint will be useless after it dries. May look ok, but comes apart with finger pressure. And if the glue gels and doesn't squeeze out fully, then it leaves a thick glue line that will never be strong even if you do reactivate it with fresh hot glue later.

Yeah, I'm no expert, but I work with hot hide glue a lot, and I definitely separate the two issues of joint integrity and shedding moisture. The joint is a good joint pretty quickly. Getting rid of the moisture normally means waiting overnight. That's what I like to do, anyway. I always have a fully dry and stable joint the next day.

Daniel,
You may have already seen this, but here's some info that Frank Ford shares about HHG that I have found interesting and useful:

http://www.frets.com/FretsPages/Luthier ... eglue.html

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George :-)

I'm pretty comfortable with the working time and application of hide glue - love its easy cleanup, and long-term repair characteristics. The theories about high strength 250g+ not being the best choice makes sense as I read it - watering it down to working consistency for lutherie ultimately leads to lower solids in the join, and potentially weaker joint than appropriately mixed sub 200g hide glue.

I can still see the value in 300g+ in cleats and potentially bridge gluing where a thicker consistency is fine, and a quick set more fuctional

A clamp time experiment with my Behlen 164g is in order, as I think I've been clamping for much longer than I need to. Would be great to free up the go-bar deck and clamps to keep projects moving. It is often the case that I have sporadic afternoons or late nights to work on instruments building, and getting things glued up in a more efficient way would be helpful.

thanks all