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Poor results with carpenters glue


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So far on my little build I've been using carpenter's glue, specifically this brand:

 

http://www.lepage.ca/en/lepage-products/pva-glue-wood-glue/carpenters-glue.html

 

I thought things were going well until it came time to take off the temporary keel guides/holders which were spot glued to the building frame: they popped right off with I think far too little effort! The wood itself was not damaged at all: the separation was cleanly at the glue interface. This doesn't seem right for a glue which is supposed to have tonnes (literally) of holding strength.

 

The only thing I can figure (and this is just a guess) is that the margin of error on the clamping force is too narrow. The fine print says to use "50 to 150 psi" and "Avoid excessive pressure,which will result in starved glue joints." How on earth am I supposed to gauge what my array of clothes, binder, and dollar store clamps are doing?!? :)

 

So, topics for conversation:

- What am I doing wrong

- What should I be using instead.

 

Thanks in advance for any thoughts and advice. Sadly I've already got the shear and garbords in place using this stuff and am now terrified. :)

Edited by Sunsanvil
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Typically when gluing wood with such glue, you spread glue evenly over the surface to be glued and clamp until it just comes out of the seam.  To much and you "starve the joint" that is, you squeeze out all the glue.

 

It's not odd at all that a couple of spots will easily break free considering there's very little relative bearing surface involved.

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To address your problem, I really would like to be able to address you by some name, even if you make one up.  What do we call you?

 

Aliphatic (carpenter's) glue is by far the most useful for wood to wood based on many many responses here at MSW and in my own experience.   I assume you had a clean surface on each piece.   Gaging clamping pressure?  I try to use clamping or  weights that would be the equivalent to modestly hard finger pressure.  Too little, too much, not good.    If you are having to really  force things together with clamps or a lot of weight, the fit is bad, not the glue. Just one opinion. 

 

Allan

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If I read this correctly: you are concerned about PVA-yellow having too weak a bond based on a temporary

bond being reversed too easily?

First - I think you were lucky that it reversed without major damage.  A different type of glue would be more suited

for the temp function -  although spot and IsoOH to dissolve would work - I just would tend to use too big a spot.

If both surfaces are totally covered before bonding, I think the "joint starve" problem is a fiction.

The glue works by undergoing a chemical reaction - polymerization - as it dries.  It essentially forms a plastic material.

With wood, I am very skeptical that all of the glue could be squeezed out - the wood fibers would crush at the clamp face

before that happened. 

The stronger the clamping force- the stronger the bond.  Although it is not realistic, the bond would be best if a single chain

could reach both wood surfaces.  A bigger problem is the nature of the wood surface. More bite is better.  I suspect that

my compulsion to use 220 grit is right at the point of the surface being too smooth.

With planking - I doubt too much force is a practical problem - too little is much more likely.

The wood surface should be free of any substance that could interfere with the penetration of the micro chains of polyvinyl as they

 assemble.

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Thanks all for your thoughts.

 

If I read this correctly: you are concerned about PVA-yellow having too weak a bond based on a temporary

bond being reversed too easily?

 

Well, now that you put it that way... :)

 

But seriously, those temp-tabs were put on the same way I've done everything else: apply glue, clamp, let dry. The concern which hit me this morning was that if all 8 of those popped off with such relative ease, what does that say about all the other assemblies I've done to date? I wonder if I need to take more care in terms of surface preparation or something.

 

B

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What was the wood species?  Some exotics have resins or oils that can prevent bonding, and the usual maneuvers are to glue freshly cut/abraded surfaces and/or wipe with acetone to remove surface residues.  

 

A reversible wood glue that forms very tight rigid bonds is good old hot hide glue. One use for hide glue is to chip glass for decorative effects.  After drying, chipping it off will result in a chip of the glass coming away with the glue.

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Maybe you got a bad batch of glue. I use Lepages Pro Carpenter's Glue and I love it.  I find it to be incredible for holding strength and work time.  The only time when I had issues was when I didn't have full coverage.  You need to make sure the piece being glued has glue fully on all mating surfaces.  When I didn't the piece would break away pretty easily.  However, so far, that has worked to my advantage.

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Everything is pre-shaped. The shear broke away at the stern while I was bending/fitting the next plank: just pushing the next plank against it was apparently too much for it, which seems absurd.

 

And in any event, the temp tabs which I mentioned at the onset were flat pieces of wood glued to flat wood. When I took those off I expected the tiny strip of wood to break, not pop off cleanly.

 

This is turning into quite a mystery.

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Maybe you got a bad batch of glue. I use Lepages Pro Carpenter's Glue and I love it.

Can you do a quick experiment for me: put a blob of it on something like a paint pallet or peice of tin foil.  Next morning, whats it like?

 

Mine seems to be very "brittle". As I recall (which I grant is imperfect) other PV type glues I've used in the past all dried to a somewhat supple/resilient blob.

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Expecting that all PVA brands should behave in a similar way:

I use Titebond II - I squeeze a working quantity onto a piece of

wax paper.  The left over material goes from an opaque tan/cream

to a clear amber an no matter how many layers build up - ( I use the

same piece of wax paper for a long time)  the dried and polymerized

glue is flexible.  If what you have is brittle when dried - it is likely a bad

lot. 

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even if you make one up.  What do we call you?

 

Looks like B cryptic still but B is better than nothing.

 

I would agree that your batch of glue sounds like it has a problem, it might have been frozen at some time in the past, either by the retailer of somewhere else along the line, My glue does exactly the same thing as Derek's sample.

 

Michael

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So here are my results.

 

Thanks for that!

 

I wonder, was yours fully cured though?

 

I got my hands on a completely different bottle from a friend. Did several blob tests. Both bottle yielded the same results:

 

Left overnight: still pliable.

 

After a full 24 hours +: Fractured into hard pieces.

 

Bad ju ju at my house? :)

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Thanks for that!

 

I wonder, was yours fully cured though?

 

I got my hands on a completely different bottle from a friend. Did several blob tests. Both bottle yielded the same results:

 

Left overnight: still pliable.

 

After a full 24 hours +: Fractured into hard pieces.

 

Bad ju ju at my house? :)

 

I am thinking, and I don't mean to sound rude, please believe me, but for the small price of a new bottle of glue, why not just replace it? It seems we have tried to help you yet you still seem to continue testing your glue thinking that perhaps it will yield better results at some time.  Perhaps try another brand or type.  Mine probably wasn't 100% cured but we are now splitting hairs.  I love the glue I use and wouldn't consider changing it.  By the way, I probably bought the bottle three years ago and it still works like a charm.

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Thanks for that!

 

I wonder, was yours fully cured though?

 

I got my hands on a completely different bottle from a friend. Did several blob tests. Both bottle yielded the same results:

 

Left overnight: still pliable.

 

After a full 24 hours +: Fractured into hard pieces.

 

Bad ju ju at my house? :)

I am thinking, and I don't mean to sound rude, please believe me, but for the small price of a new bottle of glue, why not just replace it? It seems we have tried to help you yet you still seem to continue testing your glue thinking that perhaps it will yield better results at some time.  Perhaps try another brand or type.  Mine probably wasn't 100% cured but we are now splitting hairs.  I love the glue I use and wouldn't consider changing it.  By the way, I probably bought the bottle three years ago and it still works like a charm.

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I am thinking, and I don't mean to sound rude, please believe me, but for the small price of a new bottle of glue, why not just replace it?

 

Like I said, I did get a hold of another bottle, and found it interesting that it was no different than the first. Makes me wonder if the temp or RH in my craft room is a factor. Next step will be a completely different brand but I'm still interested in the science behind this stuff and why not one but two bottles of LePage (sourced over a year apart mind you so they are definitely not from the same batch) behave differently for me compared to yourself.

Edited by Sunsanvil
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