Aging wood glue – rejuvenate or discard?

[Quourteous]

Hi All.

I came to do a furniture repair today, sought out my modest bottle of wood glue and realised that it hadn't been used in a couple of years – during which time, plastic bottle or no, it has become noticeably more viscous than it was when new.

So the question is: if I gently mix in a bit of water, small amount at a time, will that thin it out and will the glue be as good glue as it was when it was new?

And maybe a secondary question: will it work as effectively just as it is? Its consistency now is still 'workable' – I can readily spread it over the two faces to be glued.

Thanks!

 

[AC Power]

If you have some time, I would try the glue on some scrap pieces of the wood you've laying around. Let them set/dry for a day-or-two, then try to break the bond manually with your hands, not hammer or equipment. This way, your manual dexterity can "feel" to what degree the glue has bonded.

 

[Quourteous]

Good idea – thanks. I remember being told, years ago, that good wood glue is stronger than any known wood, so if subjected to increasing strain, the wood will break elsewhere than the glued join.

 

[AC Power]

I think your bang on right. I've seen it break, and it appears the wood beneath the glue separates before the adhesion of the glue itself!

 

[Quourteous]

FWIW I did try mixing water (back) into the glue, a few drops at a time, stirring it in the bottle through the neck, using a thin wooden kebab skewer.

It seems to have worked perfectly. The water stirred in readily and with only a bit of patience, the consistency returned to a uniform 'flow' throughout. The proof will be when I actually use the glue, but it seems just like new, apparently confirming that water is indeed the solvent. I'll be really surprised if it's not as good as new. Which, given that this glue appears to have been produced in 2004....

... is not bad going. Money well spent!

Now this is interesting. The Wikipedia article says that this glue, Gorilla brand, is polyurethane. It goes on to say, "When exposed to moisture, isocyanates react with water and thus cure the adhesives." Clearly that did not happen with this stuff. Quite a few drops of pure 'moisture' i.e. water were added, no curing took place, and the glue remains fluid, now a week afterwards.

You have to think that this is the sort of thing our parents would have known as second nature. Maybe not our grandparents – another Wiki article says that polyurethane only achieved widespread use in the 1950s... i live and learn...

 

[AC Power]

Well, I would say that is very interesting. I found you noticed that the "...water is indeed the solvent." Naturally, I am no chemist, but I was understanding that if it can be cleaned up (or mixed) with water, it's not an oil based product.

Isocyanates are only a few molecules away from cyanide.....harmful for our respiratory systems. Years ago, I guess the autobody industry found that using Isocyanates improved their product, however, due to gov't regulations, they couldn't use something deadly. So, I was told they chemically adjusted something to the cyanide, thus giving it a different name. A "loop hole" to use it in a manufacturing process.

Interestingly too, I wondered why my parents used "crazy glue" on my heavier natured opens wounds. I would get hurt doing dumb things, and they "shut-up" the wound with Crazy-Glue....something I thought was toxic and only used for fastening wood, metal, acrylic, etc...Well, I learnt that Craxy-Glue was developed during the War (I or II) to "close-up" serious wounds to soldiers hurt in combat. It worked, I guess, until they could get the wounded back to a military hospital. Difference with me was, I wasn't going to see anybody thereafter!!!!! Ha, Ha.....Well, Hell, I am still alive.