Dissolving hardened PVA glue

[Gerard Scanlan]

Rushing to glue up a box I did not spot it was clamped slightly out of square. #-o It is only a bit out of square but it is going to mess up the interior if I leave it like that. With the hours I spent trimming the dovetails to fit I cannot believe I messed up this part. So I got thinking is there a way to dissolve PVA wood glue (it is water based) without soaking the entire box in water. I have a vague recollection that someone once told me you could use terpentine or vinegar. The tricky part is that the lid has padouk inlays and my experience has shown me that when it comes into contact with water things get ugly. Has anyone ever managed to do this sucessfully?

 

[JakeS]

So I got thinking is there a way to dissolve PVA wood glue (it is water based) without soaking the entire box in water?

Soaking the entire box in water most likely would just ruin your wood without loosening the glue much, because while PVA is water-based, once it cures it's more or less completely waterproof.

I expect that if you will have any luck with anything, it'll be an organic solvent which dissolves PVA; try gluing some scraps up and see if any various solvents you happen to have around do anything to it. My first guess would be acetone, simply because it's commonly enough available, I know it dissolves or softens a wide range of plastics, and it evaporates relatively quickly so there's at least a small chance it won't do much damage to the wood. Although I'd expect it might do damage to wood much quicker than water, as well... and on that note, wear gloves!


That said, I think you have to expect the worst, and just count yourself lucky if something like that works.

 

[newt]

You could try heat on a test piece.

 

[MIGNAL]

I think that Methylated Spirits dissolves PVA but it might be a bit slow. Acetone (as mentioned) may do the same. Padauk leaks though!

 

[Mr T]

Hi

Meths will soften PVA. I've used it to dismantle chair joints when restoring. If your dovetails are nice and tight (which I'm sure they are!) you will find that it is difficult to get the meths to soak into the joint, so I don't think it will work. Worth a try though.

Good luck.

Chris

 

[Gerard Scanlan]

The dovetails are nice and tight but they are not pushed completely home so only stuck in one direction. So that is part of the reason for it being out of square. Serves me right for trying to do a glue up late at night just before leaving the workshop. Although because I made such a poor job of it I may now be able to save it! I am contemplating the best course of action might be to cut the top from the box as I would have done so originally anyway and then attempt to ease it apart the joints using either meths or heat (obviously not at the same time). That will make it easier to keep the padouk out of danger. I wonder if a paint stripper heat gun (you know one of those electric hairdryer style heat guns), that some one gave to me, might do the job as when you use pva in veneering you let it dry completely and reactivate the adhesive a hot iron.
It is better not to mess things up in the first place than to have to spend an inordinate amount of time trying to correct the problems afterwards, but up the side, I am unlikely to try and glue up a project in a hurry again. I had hoped that an antiques restorer or cabinet maker might have immediately known what to use. Afterall I cannot be the first person to have done something this daft.
Well I will report back when I have plucked up the courage to tackle it. I have been avoiding looking at the box for the past week carrying on with other projects as though it doesn't exist, but I cannot ignore it for much longer. I am also going to glue up a few pieces of stock as suggested and try and separate them after a few days using the various ideas.

 

[AndyT]

I know it's no comfort now, but I think an antiques restorer would say that there is no easy answer - and that is the reason why they would also advise against using PVA on anything which might stay around long enough to need restoring in future.
There are other glues available which are reliably reversible using heat or moisture, and a decorative box does not need waterproof glue on its joints.
There was a thread recently asking why we need a range of different glues when PVA would do for everything - I think your experience shows a reason why! (And full marks to you for telling us about it - "don't make this mistake" threads are really useful!!)

 

[Teckel]

As mr t said meths will dissolve PVA. You will have to let it soak into joints. You do this by a syringe which will take time. Best bet is to cut top off as you said and try to tap it apart from the inside once you have soaked. use a strong piece of wood like a 2x2 or something to that effect to lay along the inside which will give you a greater area rather than just hitting with a hammer head.
You could just try and tap it when you have the top off with out the meths.

 

[deserter]

An alternative to tapping is to use a quick clamp with the heads reversed so that it spreads rather than clamps.


~Nil carborundum illegitemi~