Choosing a Glue with a Long Open Time

      A discussion of the working time allowed by various adhesives. September 19, 2009

Question
I am planning some complex glue ups with maple, walnut, pine, etc. I need a long open-time glue. Since I do low volume, cost is not an issue. I would like to see 30 minutes as a minimum. I am not concerned with dry time. It seems the DAP resin glue is the glue of choice for this application. However, I have lots of chemical sensitivities and would prefer to avoid the formaldehydes. Are there other good options out there? No need for it to be waterproof.

Forum Responses
(Adhesive Forum)
From Jeff Pitcher, forum technical advisor:
The DAP resin you referred to is a powdered urea formaldehyde resin and will give you the longest open time of all available wood glues. You could probably use a long open time epoxy as well but it's more likely that you would have a sensitivity to epoxy than formaldehyde. There are PVAs that have a relatively long open time (as much as 20 minutes) you can find some of these at your local hardware store.



From contributor P:
We have had good luck with gorilla glue for complex, multi joint assemblies. Slightly dampen the tenons and glue the mortise. The joints slide right together.


From the original questioner:
Thanks for the responses. Gorilla glue lists about 15 minutes open time. How much time do you think you gain by wetting the tenons?


From contributor C:
As an old timer let me say this, glues are natural substances. What youre talking about are adhesives so far - if you want to glue with something use hyde glue as it will give you all the open time you need if some urea is added to it. Be sure to use one strong enough for cabinet work such as 135 bloom gram strength. And if for some reason 50 years from now the glue fails it is easy to repair by using hot water to re-dissolve it and applying fresh glue. Do not use the liquid hyde glues they are too weak. Buy ground glue and soak it in water till swelled then heat it up to dissolve it and maintain about 145 degree temp while you use it.


From contributor Z:
Titebond 3 will give you plenty of open time and is very strong and forgiving. I've found Gorilla glue to be terribly weak, and Fine Woodworking Magazine recently rated it at the bottom of their list of test glues.


From contributor P:
I think problems associated with failure of gorilla glue are due to sloppy joinery. The manufacturers themselves are responsible for misleading marketing, early-on they described it as gap-filling. Soft expanded polyurethane foam around a sloppy tenon is not going to be strong.

We make test samples of any assembly we might question, then we bust them apart. The only time we experienced test sample failures with gorilla was when we made our tenons too loose. Other than that, it is plenty strong. We always moisten one mating surface, unless the MC is already up there. Air-dried lumber is often 11-12% already. It depends on the application.

You need to follow the guidelines for the adhesive you are using; PVA, epoxy, polyurethane, hide it doesn't really matter. If your joinery is good the type of glue you use is not that important. For example, West system is very strong, but I have seen failures where both surfaces weren't fully wetted and a starved joint resulted. I've seen PVA joints you couldn't bust apart after just 30 minutes! Moistening the joint with Gorilla gets things kicking. Open time is more than sufficient for a multi-panel door frame. We have hundreds of doors built this way with no failures.



From contributor K:
Check out Franklin's Titebond II Extend. I've used it open for as long as 30 minutes without a problem. I just bought a 16 ounce bottle from Rockler for just a few cents more than the regular (non-Extend) Titebond II.


From the original questioner:
I have recently tried TB II extended, and it works well. I am surprised its not more popular. Joint fit is critical for any of these glues and I agree about proper use. The makers of the glue have spent tons of money perfecting how to use the glue. Its best to apply it the way they recommend.

Also, most joints never experience enough stress to find out if the glue was applied optimally. There is a lot of room for error, however, there are applications such as table top panel glue ups where the joint might need the glues full potential. Therefore proper application can be critical.



From contributor P:
On the Titebond II extend. How much time do you have to reposition, 30 minutes? I am curious, if you are assembling a door with multiple joints, does it tend to lock up before you get to the clamps, or do things still slide together ok? Water cleanup sure sounds attractive!


From contributor K:
It depends to some degree on how liberally one applies it - if I've got 20 minutes or more worth of gluing to apply and assemble, I'll be pretty generous with the initial applications (the thinner the application, the quicker it gets too set to move) and postpone as much as possible the actual assembly of the initial joints until I've finished applying to all of the joints. Then I'll assemble in the same order as applied. If it's not all together by about 20-25 minutes from first joint applied, it will become increasingly necessary to "coax" any further repositioning with a rubber or dead-blow hammer or through clamp force. Of course, the more repositioning that occurs beyond about 15-20 minutes after application, the weaker the repositioned bond will be.



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