Violin Forum/Message Board

[jethro]

I have just had a back plate glue joint completely fail due mostly (?) I think having not cured out wood. (see other post) About 2 weeks after
joining and after about 3/4 of the carving done on outer surface a crack appeared at bottom and then at top and than the whole seam gradualy
opened - progressing towards the center. When examined after seperation the glued surfaces were glass smooth (as planned) but had
the profile of a rocking chair bottom. Touching in center and about a 3 mm crack at top and bottom. But here is the question now .........

Being in Florida the daytime air tempature is about 90-95 degrees now.
Inside my shop is about 85-90 F. I have been mixing up small batches
of hyde glue of medium consistency. After it is fully dissolved and taken
off the warmer- it cools in about 1 hour and becomes the consistency of
jello. The next day without heating- just room temp (about 88F) it is
still jello like. The next day durring the day the glue is now a liquid.
It may or may not go to jello in the evening when the shop tempature
goes down.
The glue I was using was Behlen brand dry hyde glue. It was made in
2002. I was woried - so I got a new can - dated 2007. They both
seem to do about the same thing - but maybe the older does it faster.
also the older glue - after it goes liquid - a couple of days after that
the liquid seperates into a thicker layer and a pure water-like layer.
The new glue seems to stay a thick honey-like liquid for several days
without the seperation.

My worry is that something is happening to the glue after several days
where it is breaking down chemicaly and loosing its glue propertys.
Could this have happened to my glue joint on the failed plate joint ?

Does anyone have any idea what is happening here ?

I have talked to Behlen briefly but they didn't know what was happening
from my description.

Any Ideas ?

Anybody have a hot shop area ?

Tim

[MANFIO]

If your glue turns liquid when the room temperature is hot, it may be that your glue is too weak. The glue I prepare for joints would never get liquid in room temperature.

Prepared glue must be allways fresh. Sometimes prepared old glue can deteriorate and become liquid and unsuitable to use. Some glue brands are more prone to deteriorate than others.

Hot weather cannont be blamed, I think. In Italy it's quite hot during the summer, now and in the time of old master makers.
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[FiddleDoug]

Are you refrigerating it between uses? Hide glue is essentially the same as gelatin, and will spoil sitting in solution at room temperature. I usually only heat my glue just before I use it, and store it in the fridge between uses. Even then, I will throw it out after about a week. Sitting in the fridge, it can start growing mold after a couple of weeks. As it degrades, it looses strength.
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Doug Wall

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[KenN]

I'd guess it is a combination of the joint and the glue. Even after separating the edge should be flat. Did you glue it right after planing? If not it could have been rounded when you glued it. As for the glue, Behlen glue seems to me to be very good. It doesn't get gummy and gloppy like the other brand I have when reheating. Also it doesn't seem to loose water as fast as the other brand does. If it is rubbery it has too much water. The only downside is it does not last long after mixing at my house. A week is about max before I'll see mold. I've never had Behelin separate like that. The other glue does. As you see the Behelin is much better that the other nasty stuff I have. I know people use glue pots with glue for weeks and weeks, but I have the best luck the first heating after letting it absorb the water overnight. After that , especially with my new glue, it's a crap shoot. My basement is only 45 deg to 75 deg so I have a different set of problems.

[jethro]

Ken,
everything was kosher with the joint. It was near perfect and glued about 10 minuites after planning. Glue was mixed about medium and was mixed about 2 hours before joining.

I bought a brand new can of Behlen and mixed a little on saturday evening. Sunday it was fine (jello like) - monday when I tipped the
bowl on edge about 1/4 of the vollume was colored water with the rest
showing a slight reduction in viscosity- enough to sag when I tipped the
bowl. Like it is decompasing.

Manfeo: this seperation does not seem to be mere melting in the hot
temps. Once seperated it never goes back into a jello state- even after
warming again. It seems possible that the sustained elevated tempatures in the shop might be grestly accelerating the normaly slow
bacterial growth. I was getting ( 3 months ago) about 5 days before
any signs of bad smell and about 3 more to mold. I have noticed that
when this becomes seperated - it smells bad too !

I might try talking to behlen again !

Tim

[jethro]

Ken,
everything was kosher with the joint. It was near perfect and glued about 10 minuites after planning. Glue was mixed about medium and was mixed about 2 hours before joining.

I bought a brand new can of Behlen and mixed a little on saturday evening. Sunday it was fine (jello like) - monday when I tipped the
bowl on edge about 1/4 of the vollume was colored water with the rest
showing a slight reduction in viscosity- enough to sag when I tipped the
bowl. Like it is decompasing.

Manfeo: this seperation does not seem to be mere melting in the hot
temps. Once seperated it never goes back into a jello state- even after
warming again. It seems possible that the sustained elevated tempatures in the shop might be grestly accelerating the normaly slow
bacterial growth. I was getting ( 3 months ago) about 5 days before
any signs of bad smell and about 3 more to mold. I have noticed that
when this becomes seperated - it smells bad too !

I might try talking to behlen again !

Tim

[FiddleDoug]

Would you eat Jello that's been sitting out of the fridge for a day? I've never tried it, but I suspect that Jello would also turn to liquid sitting out. In my shop, it's either at 145 deg. or in the fridge.
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Doug Wall

www.wallindependent.com

[kubasa]

I do the same thing. I use my glue and then put it back into the fridge. I can use glue for a week this way without any mold or bad smelling glue.

[Dave Chandler]

Sounds like too-thin glue. I usually start with about equal amounts of dry glue and water, a couple teaspoons of each, and then adjust depending on what I'm gluing.

I use Behlen dry glue, but my normal consistency mixed is somewhat runny when hot, but turns to gummy within about 10 seconds when applied to wood, and is rock hard overnight. When I shut off my heat source, the pot of glue will be thick jello in about 10 minutes, pretty solid next day, more like hard candy, certainly not like jello.

The only jello-like substance around my shop, is the water jar I rinse my glue brush in between applications, only takes a few swishes of glue brush in a jar of water to give me a jello-like substance when the water is cold (I heat a jar of water and keep it nearby when gluing -- I clean my brush between applications if brushing glue, or dip my palette knive to clean it off and reheat it again between applications). This glue-water is Way too thin for use in gluing something, but it does get jell0-like.

I did have my first episode of mold this week, probably left the top off too long.
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo

[jethro]

Dave :

It is possible that my glue was a little too thin. I will try mixing 50/50
and see what it looks like compared to what I was using.
Is there any device to measure glue specific gravity to detect glue
viscosity or concentration ???? Something like an antifreeze tester with
little balls of slightly different density ?????? Would make mixing glue repeatable... Or I guess I could just measure vollume !

I'm sure my wood was green though. It is still warping even after I
seperated the halves 2 weeks ago.

Tim

[Jeffrey Holmes]

[Dave Chandler]

Jeffrey:

I'm not real scientific in mixing, I just mix by sight, what appears to be equal amounts of water and glue crumbs, and thinner for top plate.

Lately heat and humidity in my shop does seem to be affecting the glue somewhat, and I'm getting mold within a couple days, so the glue is not keeping well. Am taking suggestion of refrigeration in between. As for consistency when cooled in the jar it is more like gummy-bear than jello, but not as hard as I thought. I really hadn't paid too much attention to how hard it turned when cold, I just turn on the heat and tip the jar after a bit to see if its gone runny yet. I keep it tightly covered so it doesn't turn to skin on the top between applications.

Speaking of glue --- I did recently, for the first time, use a syringe to fill the purfling channels, and it works like a dream, no mess, no fuss. I tried to get syringes from the pharmacy -- nothing doing. Tried a syringe used for giving infants medication, but its too fat, gets glue all over the place. So I was recently poking around in a feed store that caters to farmers, and got several "one time use" with needle for 99 cents each. I dulled the point a bit on a sharpening stone (just in case I want to poke myself I want to make sure I can really feel it!), suck some glue up into the syringe, and lay it into the channel with a sweeping motion, while plunging slowly. I don't know if its the "school solution" but it sure beats the heck out of using a brush and getting glue all over the place. Clean up is a breeze, just suck some hot water in and out a couple times.
_________________
Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo