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I just thought I'd share my first Hot Hide glue experience. Since I do not have any actual hot hide glue, I went to Safeway and bough some Knox Gelatine and mixed a 1/4 oz pack with 1.5 tbs of water (per Frets.com), got it all mixed, heated, and ready for my nice Sitka top. Using the tent method, gluing went very quickly - run a bead all the way down, flatten, tape, done.

After letting it set overnight, I took the top and cut out the outline. I noticed that the joint didn't look "right". It seemed to be just off, but i couldn't explain what or why. As I was cutting out the outline, the cutoff portion snapped at the glue joint. There didn't seem to even be any glue residue on the board at all. I thought, well, if it is brittle there, I would assume that the entire top is going to be brittle also. I got out the iron - Hot Hide Glue is supposed to be repairable, right? and separated the top. Sure enough, there didn't appear to be ANY glue in the joint at all.

Now I have a top that is already cut out and will be difficult to join. Not only that, when I glued up the joint, I cleaned it up with hot water, and after separating the joint, one half of the top belongs in a lays potato chip bag. Now what?

Questions:
* what did I do wrong in the first place?
* why did my top go all wacky after separating?
* can I fix it, or do I now have a nice AAA practice top?


Advice and comments needed.
Thanks,
Steve

I would try some real hide glue before drawing any conclusions. Practice on scrap, and set a time when you apply the glue so you'll know if you took too long or not.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Ouch, sorry to hear about this. Real hide glue will have a gram strength of approx 196 or higher, not sure what Knox gelatin has. Doesn't sound too strong. If you like I could send you a sampling of some real stuff if you like. Just pm me your address and I'll get some in the mail.
Although I'm on the road to Houston and then catching a plane to Mexico D.F. so I can send it like the middle of June.

Shouldn't be too hard getting the pieces glued back together. Try the rope and board method or a joining board like John Mayes uses to put the pieces back together. Some wax paper on both sides of the joint and a way to bring them together with pressure on both sides of the joint to make it even all the way down.....did that make since?....I'm sure you'll get it right. One question, have you thicknessed it yet? Probably not, so that helps a bit.

Hope this helps,
Hutch

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

I don't want to make any blanket statements, but Knox Gelatin should be as strong or stronger than regular 192g hide glue. It's possible, I believe, that a joint, particularly a thin one, can be compromised with too much hot water clean up activity. HHG cleans best when it has been drying for a few minutes, then the gelled glue can be scraped up with a sharpened stick or a straw or something like that. It can also be cleaned with hot water after the joint is dry. Also, there is no need to clean a joint before re-gluing with hhg, assuming the joint is a good one.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

According to Frets.com, Knox gelatine has the gram strength of ~350, hence the ratio's mentioned. The only difference is Commercial grade Hot Hide Glue is derived from Cow where Knox is derived from Pig (source - Frets.com).

Waddy, perhaps you are right. Maybe I had the glue too hot and cleaned it up too fast. That could also be why my top is now seriously warped. I'm trying to correct the wavy top, and I'll experiment with some scraps next time first.

Thanks,
Steve

But why bother messing around with an unknown? I would think that all violin makers (and some guitar builders) use commercially prepared hide glue for a reason. I mean sure, perhaps some have had success with Knox gelatine, but given how inexpensive hide glue is, I wouldn't want to stake a guitar on using a substitute. My recommendation is for Milligan and Higgins hide glue. I believe it to be much better than Behlen's or other manufacturer's with respect to ease of preparation. Other hide glues require much longer cold soaking. M&H also has greater clarity.

Also, you say too hot, but do not specify the exact temperature. Did you not use a thermometer? Hide glue should be used at the specific temperature of 145 degrees F, and the wood should ideally be prewarmed, to reduce gelling on contact.

Neglecting the glue issue for a moment, and assuming that some other agent might have also been at work, how did you prepare the edges? If you used a shooting board with a plane that had previously been used to plane wax coated wood, it is possible for wax residue to transfer to the edge, and this may interfere with the bond. Always clean planes well before planing edges to be glued.

Should probably re-name this thread "First Experience Trying to Make My Own Hot Hide Glue from Gelatine"

If the gram strength is 350 as you suggest, then open time would be much reduced from standard 192 gram and the problem you have experienced may well have been the result...That said I would like to know if Knox has ever actually tested the gram strength of their product which is manufactured with an intent for human consumption, and if so, why would they bother? The point here is that if they don't have that data, then anyone suggesting what the gram strength could be can only do so by guesstimation, and it would need to be a pretty open one at that.

You asked what you had done wrong in the first place?

The answer would seem pretty obvious, you failed to buy proper hide glue and instead tried a make shift solution. Considering the critical nature of the glue joint upon which you chose to conduct your experiment, it was risky business indeed and you were luck it failed when it did rather than on the finished instrument with so many hours invested....cheap lesson.

Cheers

Kim

I like to let my HHG buggerfy and rub it out. Hot water can weep out the mix much like Waddy stated. It cleans up easy compared to tite bond when it cures up . I can see the benefit if HHG over tite bond. I admit that I didn't think there was a difference but I am seeing one . I also admit that after 130 guitars my skills are better and I dialed in my bracing for the sound I like .
Still joint mating is critical . If you force a joint , you are doomed to failure .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Personally I never try to clean the glue line on joined plates. You should have just a bit of squeeze out that scrapes or sand easily when dry.
I do not know if Knox gelatine works or not, if Frank Ford says it does I'm inclined to think it does.

Get the hang of it, mix some more, it should have the consistency of maple syrup, even thicker. Your glue should be between 140º and 160º in the glue pot, preferably in a water bath. Was it hot enough? Did you get squeeze out or was it gelling as you glued your plates? Ambient temp. in your shop will set how much open time you have, the warmer the longer.

For your top it should return to flat with a weight on it, what's the RH in your shop? You can re-joint it, and re-join it with tape. Do a couple of dry runs before…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

As Laurent states, the tape method to re-join. It's also a quick, fuss free method, less chance of the glue gelling. Makes even more sense now that the outline is cut out.