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HHG open time
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=27584		 Page 1 of 1
Author:  coke_zero [ Thu May 27, 2010 6:55 am ]
Post subject:  HHG open time
I know I'm full of questions lately but I have started to use HHG and have a few issues. I followed the same mixture as someone posted on this forum heated it and left it overnight in the refrigerator. I then heated it and did a few tests. It glued like a rock and I ended up splitting the wood before breaking the joint. [:Y:]

So I went down the shed and got my back plates ready to glue. Heated up the glue and as quickly as I could applied the glue and got it clamped. However, it starts to gel almost instantly. I think it is actually starting to set before I even get the joint together. The glue is fairly thin and runny and is very sticky though. Is this just my inexperience with HHG and me being used to more open time or is it something to do with the mixture?

Any ideas would be great.
Author:  Haans [ Thu May 27, 2010 7:05 am ]
Post subject:  Re: HHG open time
Did you use a heat gun to heat the parts up? You have to be fast and all set up before spreading the glue. I use the back sanding dish to get it down fast and 4 clamps on that pretty much gets it clamped. Then I add clamps between and let it sit overnite.
Author:  Michael.N. [ Thu May 27, 2010 7:45 am ]
Post subject:  Re: HHG open time
Be careful with heat guns. Too much heat and you may well change the fit of the wood. Gentle heat with a hairdryer is preferable. Keep the workshop warm (close doors/windows). Do a dry fit first to make sure clamps etc.are at hand.
The common mistake for beginners is to make the glue too thick. A thin vegetable oil is near what it should be.
For Back/soundboard joints I use the masking tape method. It is both a simple and fast method. Just note that not all masking tape is made the same. If you use this method you really need the type that allows some stretch.
I once glued up 22 pieces of veneer strips in a single go (for mosaic rosette making). I timed it at 4 minutes from applying the glue to putting the log into the clamping jig. Every strip was laid out in sequence, all on a wooden work board that was pre heated. I also had an overhead heater pointing at the veneer strips. Every single strip glued fine. It's all just a matter of practice.
Author:  Haans [ Thu May 27, 2010 8:32 am ]
Post subject:  Re: HHG open time
Ah, sorry, misread. Back plates...
Of course you don't turn the heat gun up to 11. A hair dryer works too. I taper my plates from front to back, clamp down a couple of maple sticks about 1" x 2" x 24" to a laminate board at an angle so that when I tap on the back end of the plates, they wedge together. Lay down some wax paper, heat up the plates separated by about 1/4", run a bead of glue, tap the ends till they wedge together well. Lay another stick and wax paper over the joint and clamp at both ends. Done.
Author:  Laurent Brondel [ Thu May 27, 2010 9:56 am ]
Post subject:  Re: HHG open time
A few observations: a thicker mix will have more open time and much less chances of starving the joint. Opinions differ, but to glue plates, braces, blocks and so on I like the consistency of the glue to be like warm honey if that makes sense. Not thick, but not runny either. A 200W hallogen over your work station will help keep things warm. No open door, window or AC running during assembly. I use a 1500W heat gun to warm the parts: the object, of course, is not to char the wood.
Lately I've been using CA to join the back plates.
Author:  coke_zero [ Thu May 27, 2010 5:14 pm ]
Post subject:  Re: HHG open time
I have tried using the advice given tonight and plan to leave it overnight to glue. I hope it will set fine however I have a feeling it isn't going to.I heated the wood for about 5-10 minutes before hand and got it joined quickly, but it doesn't seem right just by looking at it.
Author:  WaddyThomson [ Thu May 27, 2010 9:49 pm ]
Post subject:  Re: HHG open time
If your HHG is at the right temperature, and you are using the 192 gr, strength, and your room is above 70*, you should have at least 90 seconds of open time, which should be enough to apply and close the joint without rushing.
Author:  Daniel Minard [ Thu May 27, 2010 11:01 pm ]
Post subject:  Re: HHG open time
Thanks for mentioning the squeezeout issue Todd. I'm sure that's why I had trouble with my early hide glue efforts. I was going for minimal squeezeout & the thin glue line was cooling too quickly.
Author:  Michael.N. [ Fri May 28, 2010 3:25 am ]
Post subject:  Re: HHG open time
coke_zero wrote:
I have tried using the advice given tonight and plan to leave it overnight to glue. I hope it will set fine however I have a feeling it isn't going to.I heated the wood for about 5-10 minutes before hand and got it joined quickly, but it doesn't seem right just by looking at it.


I doubt that you will be able to tell just by looking - unless you have an open joint. 5 - 1o minutes heating it is a long time, although it has been cold in the UK over the last few days. That said I haven't needed to heat a centre seam, even in the depths of winter.
If it hasn't glued well you may be well advised to do more practice runs on scrap timber, even try some rubbed joints. It doesn't matter if the practice pieces are only 6 inch long, the objective is to get the 'feel' for using the glue.
Todd's advice about squeezeout is important. You don't want a starved joint. I apply the glue to both the board edges twice, closing and reopening the joint for the final application.
Author:  Bob Garrish [ Fri May 28, 2010 9:58 am ]
Post subject:  Re: HHG open time
Like Laurent, I like my glue a little thicker. Honey sounds about right; I want it so that it runs off the brush but is thick enough that it'll still leave a 'coating' over the bristles thick enough that it almost encapsulates them. I'll throw water in or cook it off if I want it thinner or thicker without worrying too much about it.

If the clamping and joint are good, and the glue isn't too thin, then hide glue 'just works'. If it doesn't work, then one of those two went wrong. One thing I think happens a lot more than people notice when clamping is that they don't apply strictly increasing pressure across the work, so they might apply a bunch of pressure somewhere, then reduce it when they work somewhere else...which means they squeezed out the glue and then opened up that section of the joint a bit. Since it had already been closed, that section of the joint only had enough glue in it to fill the gap and now doesn't. Hide glue punishes you much more readily for that mistake than most other glues. I think the 'starved joint' is a straw man for a bunch of mistakes people don't know they're making.
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