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I'm using LMI's white (polyvinyl) glue for the first time on a build. Could any of you more experienced with this glue tell me what set times you are using before unclamping? Right now I am especially interested in the back and top brace glue-up, but I would also be interested in the set times you commonly allow for top, back and other LMI glue jobs. Right now I think I am probably waisting too much time by allowing too many hours before unclamping.
Thanks,

Bill

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Formerly know as Mandodiddle.

Hi Bill,

I've got LMI white drying up in the shop right now...at 70 degrees and 50% RH it's getting hard beads at 1 hour...I can take the go-bars or clamps off then, but I don't work the joint (for a top or back) for another hour...if it's a bridge or a fingerboard, I go 6 hours...that may be too long, but I'm paranoid about those two...hope that helps!

Larry

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http://www.presnallguitars.com

I have been using LMI glue for quite some time. I am bracing a top and back right now. I have always allowed 1 hour in clamps or go bars and 8 hours for bridges. One hour is also enough for joined backs and tops.

If you question the 1 hour clamp time, I suggest that you glue a few scrap pieces of wood together, wait an hour and then try to get them apart. I find that when you break apart a joint after even a half hour, you get plenty of wood splinters left on the glue joint.

Mike Franks
http://www.mjfranksguitar.com

It says not to stress the joint for 24 hours on my titebond bottle.You mean i've been waiting too long?

I second that. Another good test for joints that may get stressed soon is for creep. Bend a couple of pieces of wood together in a curve (a 15' radius dished form works well). Clamp for various lengths of time and compare springback. Clamp one for several hours to compare the rest to. My experience is that the times on the bottle are extremely conservative, particularly in a warm dry shop.

Check with different woods too.

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http://www.chassonguitars.com

I have a book in building guitars by Jim Williams that says to let the glue dry completely a couple of days when glueing a rossette in the channel.pg.11 So does it really take a couple of days as he says to dry completely?

I have been waiting 2 hours to unclamp and at least 4 hours to do anything else.

I think that it should be said though that the times that some of us are providing are for optimum shop conditions say 45ish% RH, 70+F.

Not all builders build under optimum conditions you can see it in the posts that we read here. If your conditions are not optimum don't be afraid to double the times that you see here.

Also, although I don't use Titebond or LMI for bridges many do and that is what I would call "stressing" the joint..... Wait at least 24 hours for that.

I still wander why Jim Williams would want you to wait for 2 days on a rosette? That seams like a long time to me also.

Mark buddy and he is using Titebond or LMI?

Yes,I believe so.

I have used titebond on my native american flutes for years and have notice when shining a light down the chamber the next day after glueing that the glue wasn't completely dry. so i always let them dry for three days before releasing the clamps.Maby lack of air flow in there though.

Mark, I'm guessing that the reason Jim Williams suggests 2 days dry time for the rosette is to allow for any shrinkage as the glue and rosette lose moisture. If you sand the rosette flush too soon, you might have it shrink back to a slight recess.

Good point on the shop conditions, Hesh. Higher humidity or lower temps could slow the cure time on the glue.

Mike Franks
www.mjfranksguitar.com

So it looks like the times vary for different operations.I usually wait 24hrs. to be on the safe side when glueing.Better to be safe than sorry.Titebond is all i have ever used since i started building electric guitars in 1985 and have never had a joint fail to this day.I just got done glueing some braces on my plates and i waited 24 hrs. on them as they are radiused and under some tension.

Once again you guys have come through! Thanks a bunch for all the good info. I feel much better now.

Bill

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Formerly know as Mandodiddle.