Adhesive with a long open time

[Jim Becker]

I'd use T-88 epoxy for this situation...that's actually why I originally bought it: a complicated glue-up that was going to take time to get "just right".

[stephen thomas]

Random notes:
The problem with urea glues is that they have about a 20 year half-life in service. Urea-formaldehyde resins self-destruct over time, more so with increased heat.

WEST epoxy addressed the concern about darkening/thickening hardners over extended storage life a few decades ago and found that the older products actually produced slightly stronger bonds. The staining can be an issue, though.

I used the original Titebond extend, which is a great glue. Originally it had great open time, and was the most rigid, strongest developed strength joint of the entire Titebond line-up They changed the formula (acknowledged) - i forget what it corresponds to now. Still use it, but not quite the same. It's now not much more open time than the original but i think it is a slightly stronger version.

I've been using WEST since the late 70's/early 80's. Some years 2 or 3 C units (5gal units) Then sometimes there would be a 5 or 6 year span where a C unit would last the entire time for only small projects. Never a problem with use. I think many of us were reluctant to move to much cheaper products as they came out, because WEST is so reliable/predictable, and has a good system for dispensers, hardeners and engineered fillers.

So long as WEST is mixed well in a round smooth-sided container, then spread out into, say, a paint roller pan, it will last at least the predicted open time for the temperature and hardener chosen. If it is spread quickly on all mating parts, it can allow well over an hour assembly time before all the clamps need to be on. For complex jointery, it is nice because things go together like they are greased. Unlike Titebond or others that can grab and seize up with a delayed attempt to clamp.

smt_bentarch glue-up.jpg

[Kevin Jenness]

Random notes:
The problem with urea glues is that they have about a 20 year half-life in service. Urea-formaldehyde resins self-destruct over time, more so with increased heat.

Please expand on this. I can believe that the rigid glueline could be a disadvantage in some situations like crossgrain joints subject to moisture cycling. In his book Professional Cabinetmaking Alan Peters mentioned a UF failure in mortise and tenon chair joints and his preference for more flexible pvas. I would think though, given the widespread use of uf adhesives in veneer work and plywood manufacturing that this would be a widely known and disqualifying issue. Can you provide some documentation?

[Maurice Mcmurry]

No problem with Urea-formaldehyde (so far) on these 39 year old exterior doors.

IMG_20210813_075630700.jpg IMG_20230310_140850164.jpg Scan_20220320 (4).jpg Scan_20220320 (2).jpg

[Alan Lightstone]

I just purchased some West Systems 209 Extra Slow Hardener. The web site says: Pot life of 40-50 minutes at 72°F, and working time of 3-4 hours. Haven't used it yet, but should give me plenty of time for my complicated glue-up.

[andy bessette]

Please expand on this. I can believe that the rigid glueline could be a disadvantage in some situations like crossgrain joints subject to moisture cycling. In his book Professional Cabinetmaking Alan Peters mentioned a UF failure in mortise and tenon chair joints and his preference for more flexible pvas. I would think though, given the widespread use of uf adhesives in veneer work and plywood manufacturing that this would be a widely known and disqualifying issue. Can you provide some documentation?

I have seen instances of its failure in much less than 20 years, where it has literally turned into powder, with no adhesion whatsoever. These issues were all seen where it had been used by other boat builders.

[Tim Andrews]

OP here, just checking in after posting my question last night. Wow, thanks for all the great replies! This has been a very informative discussion. I want to give epoxy a try, of course I’ll make some test joints first.

I haven’t searched yet, I’m assuming the better products like West or Totalboat must be ordered online as opposed to being available at the local Borg? And is my understanding correct that some epoxies are for adhesion, and others are for pouring into forms for projects like tabletops? Thanks again.

[Kevin Jenness]

I have seen instances of its failure in much less than 20 years, where it has literally turned into powder, with no adhesion whatsoever. These issues were all seen where it had been used by other boat builders.

To be fair, uf adhesives are not marketed as waterproof or for boatbuilding uses exposed to severe moisture cycling. Can you describe the typical uf failure scenarios you have seen? Have you seen that sort of problem in more typical interior environments?

edit: I did find this report from the FPL about moisture/heat degradation of uf bonds. https://www.fpl.fs.usda.gov/documnts...4/river94c.pdf

[Kevin Jenness]

[QUOTE=Tim Andrews;3315590I haven’t searched yet, I’m assuming the better products like West or Totalboat must be ordered online as opposed to being available at the local Borg? And is my understanding correct that some epoxies are for adhesion, and others are for pouring into forms for projects like tabletops? Thanks again.[/QUOTE]

West System products can be found fairly widely at suppliers like West Marine, but generally your best bet is online. There are a lot of specialized formulations for clear coating and deep pours/casting so do your homework.

[Maurice Mcmurry]

Jamestown Distributors has been my source. The slowest version I have tried is the "Tropical" hardener. It is very slow.

https://www.jamestowndistributors.co...xoC__gQAvD_BwE

[John Kananis]

I like both west systems epoxy and unibond 800 for longer assembly time.

That said, I don't think anyone has asked what application this is for? And oftentimes, you can use standard pva glue if you glue in sections. Assemble the entire project and then glue the last element in place. When that sets, remove a piece, apply glue and put back in the clamps, rinse and repeat until all the joints are glued - this method also guarantees that everything fits together properly.

[Tim Andrews]

Thanks again for the recommendations. Unless I’m using exposed joinery like dovetails or box joints, I usually use my Dowelmax because I like the speed, strength, and accuracy it provides. For a larger piece, that can add up to a lot of dowels. I understand the process of gluing in sections; dry fitting the entire piece, disassembling a section, applying glue to only that section, and then reassembling and applying clamps, rinse and repeat. Just want to explore the options that a longer open time offers.

[stephen thomas]

Please expand on this. I can believe that the rigid glueline could be a disadvantage in some situations like crossgrain joints subject to moisture cycling. In his book Professional Cabinetmaking Alan Peters mentioned a UF failure in mortise and tenon chair joints and his preference for more flexible pvas. I would think though, given the widespread use of uf adhesives in veneer work and plywood manufacturing that this would be a widely known and disqualifying issue. Can you provide some documentation?

Please expand on this. I can believe that the rigid glueline could be a disadvantage in some situations like crossgrain joints subject to moisture cycling. In his book Professional Cabinetmaking Alan Peters mentioned a UF failure in mortise and tenon chair joints and his preference for more flexible pvas. I would think though, given the widespread use of uf adhesives in veneer work and plywood manufacturing that this would be a widely known and disqualifying issue. Can you provide some documentation?

When i started woodworking as a kid in the late 50's/early 60's, about the only glues out there for "consumers" were liquid hide glue, and Elmers.
Elmers did not work well in my then limited experience (I recognized later that it does have uses) and hide glues failed when they got wet, especially the "liquid" versions.
I remember taking a (small) creche i made in 4th or 5th grade woodworking/craft class for the school display home after Christmas. It was a long bus ride on a very wet, rainy day, and the parts were shifting after the first bus transfer. By the time i hiked up our lane, it was just a handful of molasses coated sticks. By HS i was exposed to Weldwood plastic resin glue, but did not have good luck with it (my learning curve, not the product. Possibly combined with outdated glues in the local sources, or storage.) Later in my working life i was exposed to all sorts of glued wooden assemblies. I was struck at some point how many failed assemblies and delaminations were apparently initially stuck together with Urea glues. That had turned to powder.

When i got older and started woodworking professionally, i made a point of researching the options as much as could be found in books Remember, you could not just go online and search the FPL in those days.
In 1978, "Adhesive Bonding of Wood" M.L Selbo came out and essentially was a compendium of various FPL papers and experiments of a range of glues in a range of wood substrates, over all kinds of conditions and time spans.
Regarding Urea resins, it became apparent how easy it would be to not use urea glues optimally. In tests, yes, the glue, substrate, and environment really do need to be above 70F before and while being pressed, the press time really does have to be in tons, and the duration of pressing really does have to be "long". There are many ways to go wrong just in the prep stage, and while prepping to clamp (very limited open time). In an industrial setting when separate stronger acid catalysts are used, the opportunity for mayhem in later years increases. (While most small shops do not use separate acid catalysts, it is mentioned as yet another possible gremlin that may have occurred when inspecting a failed manufactured item.) Apparently, the room setting formulations are the least durable, except only for those that are extended (say, with wood flour).

The section in ABoW about urea durability is almost an attempt at an apology, and describes all the ways that if it was perfectly pressed, and perfect environment, it will generally be pretty good, maybe even excellent for fortified types. (not room temp curing) After working down through extreme temperatures for failures that a typical item is not normally exposed to, it eventually notes that "...less significant weakening of room-temperature-setting urea resin glue joints has been observed in birch plywood under continuous exposure to 80F & 65% RH. The rate of strength loss is increased by high humidity at 80F" & above. Kind of sounds like most of central and eastern US over a long summer for high humidity, and the whole country for extended periods above 80F Unfinished specimens can deteriorate faster. A summary includes "Nevertheless high-quality urea resin glue joints do appear to be sufficiently durable for nonstructural interior applications within the human comfort range of temperature and humidity conditions. On the other hand particularly with high shrinkage, dense species, the more durable resin adhesives {referring to phenol resorcinal and melamine adhesive, e.g.} would assure longer trouble free life"

When i started messing about with small airplanes, "plastic resin" glues were approved for primary structure. Sometime in the past few decades, they became prohibited. While an airplane is very well likely to be exposed to wider temp and humidity conditions, routinely, than, say a credenza, the stark fact remains that the glue turns to a powder and fails. My experience with inspecting or sometimes repairing other manufactured items; and i believe i read this somewhere, is that about half the remaining joints fail on about a 20 year basis.

Hot hide glue has a better service history. The real factor for me is that it can be repaired when it does fail, so i use it for traditional repairs and some assemblies.
Titebond (family) works for mechanical joint assemblies that are not exposed to outdoor conditions.
Phenol Resorcinol is for exterior intended to last "forever" assemblies especially laminations.
Epoxy is for "nearly forever under "most" all conditions where the wood won't fail first. And for when i need a very long assembly time.

The deterioration rates and weaknesses of the glues i do use are known and predictable.
Urea resin seems a whole lot less so, and it offers no advantage to me that is not better served by one of the others.

It is not important for me to "convert" anyone. There could certainly be reason in many peoples work to use room-temp-setting Urea glues.
If you have reason besides my experience and caution, the FPL can now be researched online. If you find counter information as part of a complete analysis, please post it.

smt

[Mark Hennebury]

Thanks Stephen.

[Kevin Jenness]

Stephen, thanks for the explanation. What experience I have (relatively little) with room temperature setting uf glues has been veneering interior millwork which has not been exposed to extreme conditions and as far as I know has held up ok. I agree with your assessment of other classes of adhesives and am not an advocate of uf glues in general but I will be even more skeptical in future thanks to your post.