The lowdown on wood glues

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tvrgeek

tvrgeek

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My tests are still sitting in the shop sinking in. Only the epoxy covered with poly resin seems to have held up. (West 407) and is not showing the seam. I have my budget SilverFlute project with poly resin as glue under poly and will see how that holds up. In only two months, no shadow line yet.

Good test. I can add, super glue is terrible. So was the new wonder-glue anythings glues as they just soaked in instead of gluing. The problem for speaker builders is the long term shrinkage of the glue revealing a dip in the finish at the joint line. Yellow glue is especially bad.
 
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wintermute

wintermute

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Thetwinmeister said:
Interesting, did you document your tests anywhere? I would like to know more.

Specifically, I am interested yes, in strength, but largely in the ability to create an air-tight seal. A website suggested Fulaprene 303. Has anyone heard of or used this glue?
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I used it (not 100% sure it was 303) for gluing the ports into my BR enclosures years ago. It is good for gap filling (my holes were slightly too big for the port). I don't think I would try to use it for joining MDF panels though. It is quite thick and may not squeze out of the joint like a PVA would, but we are talking 10years+ ago that I used it so memory may not so good. I think from memory it also does not dry rock hard (remains somewhat flexible) so I suspect it would not be good for sanding and finishing.

It may be good from a decoupling point of view though... say for gluing a baffle to the box.

Tony.
 
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Thetwinmeister

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Joined 2011
evanc said:
Try unibond 800.
Vacuum Pressing Systems -- Veneer Glue
It dries hard as a rock and is thin so it will soak into the grain and lock it up a bit.
Evan
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Thanks for the reference, it looks like that is a PVA based glue. Promising, I will look into it.

wintermute said:
I used it (not 100% sure it was 303) for gluing the ports into my BR enclosures years ago. It is good for gap filling (my holes were slightly too big for the port). I don't think I would try to use it for joining MDF panels though. It is quite thick and may not squeze out of the joint like a PVA would, but we are talking 10years+ ago that I used it so memory may not so good. I think from memory it also does not dry rock hard (remains somewhat flexible) so I suspect it would not be good for sanding and finishing.

It may be good from a decoupling point of view though... say for gluing a baffle to the box.

Tony.
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Oh, this is very good to know. I can't find any other hits on Google for a Fulaprene that is not 303, so it was most likely indeed Fulaprene 303. I may buy some just to experiment with. The idea of baffle decoupling is new to me, I was always under the impression bracing the heck out of the baffle was the way to go.
 
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Thetwinmeister

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evanc said:
Unibond 800 is a modified urea resin formaldehyde two part adhesive with a translucent liquid resin and a powdered catalyst. Unibond 800 is designed to provide a rigid, gap filling glue line with faster than usual set times.
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"Unibond One is our newest offering in the Unibond family of gluing products. Unibond One is a one part PVA adhesive specifically designed and formulated for wood veneering and laminating providing a extra hard glue line, long open work time and will block bleed through on commercially sliced veneers."

I read that first, thought you were referring to it.

Based on what I have read about glues, formaldehyde based wood glues are not as strong as PVA wood glues. The two part nature is also unappealing. Have you used Unibond 800? (not to be confused with unibond One hah)
 
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evanc

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I use the unibond 800 for most of my veneering. It does an exceptional job controlling the veneer. pva glue joints are very strong, stronger then the wood in fact as long as you have perfect long grain mating surfaces. pva is no good if there are gaps. pva also does not dry as hard as the unibond...it allows the veneer to creep or move seasonally.
I think this movement might be part of why people are seeing there glue lines after some time.
Another thought on seeing the joint after some time is that the wood has either grown or shrunk since the glue hardened showing the joint.
Evan
 
dirkwright

dirkwright

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Joined 2011
Horses for courses... PVA glues require air to cure, which may not be available under a veneer, but PVA is great for wood joints and things like biscuits and dowels. Urea based glues don't require air for curing, as I understand it, so they are better for veneer work, though I think there are some PVA's designed for veneer now. As always, adequate clamping is required for a good strong wood glue joint. If you are concerned about seasonal wood movement, you could soak your wood with CPSS epoxy, though that would be expensive.
 
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