WWA Info Exchange

I have a 2/3 full tub of powdered plastic resin glue (Weldwood brand) that has been tightly sealed for perhaps a year or more. I mixed up a small batch to 'practice' working with it in prep for a project. The project involves bending several thin strips in a form, just a simple arc. I had soaked the strips for about six hours, then pressed them into the form overnight to take an initial bend making the glue-up easier. Left the bent strips to dry overnight, out of the bending form. Mixed and spread the glue, clamped the strips in the form and set it aside for 24 hours. I had mixed way more than I needed so I grabbed a few pieces of scrap wood and simply stuck them together with enough hand pressure to squeeze out as much glue as possible, no clamps.

Today, almost 24 hours after all that I released the clamps and the strips pretty much came apart at the seams. The pieces of scrap wood were fairly well bonded although I didn't test them to failure.

My first diagnosis is that the strips glued up in the form were far too wet, still, for the glue to have cured withing 24 hours, if at all. Soaking in plain water is clearly not the right approach in that case. Does steaming increase the moisture content to the degree that plain soaking does? I'm also thinking that a heat gun might be the best of all??

But in the back of my mind I thought perhaps the glue might have deteriorated. I don't see how age would affect the powder but I thought I'd ask.

_________________
Nullum Gratuitum Prandium

Cheers - Dennis

Steaming won't wick unbound water into the vessels like soaking will, so steaming will dry a bit faster. Other benefit with the steam is the lignin is hot enough to creep, so you'll get less springback.

Pa was a big Weldwood user, and sometimes he'd have a break in projects that would give him a can of year old powder. No ill effects that I can see, and some of his furniture is fifty years on down the road.

Bob Smalser posted about some testing he was doing with adhesives a year or two back and I recall being quite surprised that he said that plastic resin glue only had a 1 year shelf life. I would have thought that the unmixed powder would last indefinitely but apparently not.

I was unable to find the post using the Search function. His profile shows he has 958 posts but the search engine can only find one. What's up with that??

Bob

There may be a limit to storage capacity on this setup, Bob. FIFO, First In First Out as we used to say - by way of explaining Smalser's post not being available. Dunno - perhaps.

Got another 'experiment' glued up yesterday afternoon that I'll leave in the clamps for 24 hours. This morning the squeeze-out is still a bit soft to the thumbnail test but it looks to be setting up OK. Another thing, I suspect sloppy measurement on the first 'test' resulted in a too thin mix. Paid more attention to it this time.

The interesting thing about this stuff is that it appears to have an extremely long pot life but just because it's still fluid after a couple hours doesn't mean it's still viable as an adhesive. Tried using some that was two hours old in the mixing pot and it didn't seem to bond very well.

Interesting stuff, though.

I'd really like to find a single component glue, one you didn't have to mix, that isn't water based. The moisture in the glue seems to cause the edges of my veneer to curl up just perceptively (using Tite-Bond) although the bond appears to be quite good. I end up doing a lot of scraping and sanding to get a level surface.

_________________
Nullum Gratuitum Prandium

Cheers - Dennis

Hey Dennis,

In my experience dry, urea formaldehyde glue definitely has a shelf life. In fact, I recently had a project fail because of old glue. Interestingly, although the manufacturers of liquid UF glue also warn of a shelf life, I've had fewer problems with old liquid glue than old dry glue. URAC -185 and UniBond are two good choices.

Oh, BTW- Steaming removes moisture from the wood once it's dry of the steam. It has the same effect as kiln drying.

_________________
"There is no path to peace, peace is the path."
Mohandas K. Ghandi

Lots of information here. http://www.dap.com/docs/tech/00030205.pdf

Interesting information about preferred moisture content of the wood at no more than 12%. Sounds like that's where your problem lies. Since it doesn't just dry, but cures chemically, there may be some time after which the cure will not be good even when it finally dries.

Hey George,

I think that Dennis' problem is with Weldwood Plastic Resin Glue, which is a urea-formaldehyde glue, and not with Weldwood Resorcinol Glue.

Tom

_________________
"There is no path to peace, peace is the path."
Mohandas K. Ghandi

http://www.dap.com/docs/tech/00030201.pdf Once again, mixes with water, but chemically cures. If the water's in the way ... well, anyway they say one year minimum shelf life. Not sure that they stamp a sell NLT date from which to reference it.

Really appreciate the ongoing discussion.

I realized my biggest problem was not doing my homework before trying to speak to the class.

The label clearly states that a 70 deg environment is minimum, or so as I read it. Thus far this spring I don't think we've had more than two days of 70 degree weather. (Love NW WA. don't we, Tom!) It may have been about 60 in the shop when I did my dry run

No date of mfr appears on either of the two containers I have. Many, many hours of web downloads (dialup whine) clearly indicates that there's a life span to this stuff. I have a hard time believing it but that seems to be the consensus out there.

I've got two tubs of this stuff so I'll probably go ahead and use it regardless. I'm not building bridges or anything.

_________________
Nullum Gratuitum Prandium

Cheers - Dennis

Dennis- I've recently used weldwood plastic resin glue and certainly noticed that heat had a significant factor in curing-- I also believe I read online somewhere of an artist that made bent wood laminations that would wrap his glue-ups in an electric blanket to promote quicker curing. I know that even here in Tucson I left my glueups for 15+ hours before taking them out of my vacum press. (I also would put my press bag onto the back black cover of my pickup truck to dry where it was warmer, but this was a few months ago) I'm not 100% convinced that the "one year shelflife" is a "milk gone bad" type scenario as I believe that there are a TON of factors like heat, humidity, number and speed of temperature changes, storage location, etc that could factor into the glue going bad. I can't help but think that the manufacturer is hedging their bets a little with the "one year" rule... especially when they (as you pointed out) don't date the containers.

I'd try doing a glueup and moving into a warmer location (or warming the shop?) with a small test glueup to see if that alleviates the problem.

Good luck and please let us know

Lawrence

Hey Dennis,

All urea-formaldehyde glues require a warm cure. I use Urac for the bamboo backed bows, like the one I made for you. And I always use the electric blanket, regardless of the ambient temperature, just in case.

Tom

_________________
"There is no path to peace, peace is the path."
Mohandas K. Ghandi

Ya know, Tom, I bought an electric 'throw' a small electric blanket for just that very purpose during winter projects in my then unheated shop. It never never considered it necessary to supply heat to the glueup at the end of June! (grin) I guess one could approach working with these types of glues in the same manner as epoxy.

_________________
Nullum Gratuitum Prandium

Cheers - Dennis