Adhesive with a long open time

[Tim Andrews]

Greetings All,
I’ve done a search here, but all the threads I have seen are old. I would like a recommendation for an adhesive with a long open time for complicated glue ups, minimum 30 minutes,. I typically use Titebond 3 but would like more time for some projects. Sometimes it’s possible to do the glue up in sections, but not always.

Titebond Extend has a lot of negative reviews, unless it is now better, so it seems the other options would be hide glue or slow set epoxy. Are these glues as strong as PVA glues? How about dealing with squeeze out? It seems that epoxy would be problematic. Obviously I would want to avoid visible problems when a finish is applied.

Thanks for any advice!

[David Zaret]

i use urea resin for such things. Unibond 800, and i thicken and tint it to get the consistency and color i want. very long open time, but requires some amount of heat to cure - if it's 40 degrees, don't use urea resin. if it hits the 60s or 70s for a few hours, you're fine.

[Michael Burnside]

I use epoxy often. Totalboat with med or slow hardener or System 3 T-88.

Almost every project I build uses epoxy in part of the glue-up. You need a lot less than you think, in fact I think people often apply too much traditional glue too. It's like they forget about long-grain adhesion on wide panels or they forget the tenons are the real strength. <stands on soap box> Glue pouring all over your workpiece isn't "better" or a guarantee that you got adequate glue, it just means you don't know how much was needed in the first place <steps off>. With epoxy you don't need a lot of pressure in clamps so, with practice, you can get a super strong bond with little to no squeeze out. It is also easy to clean up with acetone if you need to. And, like traditional glues, I will often use blue tape around critical seams, inside miters, etc.

Often times glue-ups are complicated due to joinery, so another approach is to glue things in parts. For example, I will often pre-glue my Dominos in place using TB quick-and-thick as it dries pretty fast, letting me get to the next step in about 30-60 minutes.

[Kevin Jenness]

David and Michael offer good advice. Unibond 800 and powdered plastic resin glue are similar urea formaldehyde formulations but Unibond has a lower water content when mixed. Unibond had some reported random problems with staining in the past and it was recommended to mix thoroughly, let rest for 5 minutes and mix again. They may have reformulated to avoid that problem as I have not seen any recent complaints. UF glues have a shelf life so it's a good idea to do a cure test sample on any old stock before committing to a project.

Epoxy is a reliable adhesive with the longest assembly time of any commonly used product. It gradually thickens and can be clamped into place even as it starts to cure, and it makes assembly of mortise/tenon and similar joinery relatively easy as it does not tack and stick like pvas. Curing is an exothermic reaction so it is important to pour out any concentrated volume into a shallow layer to avoid premature cure ("kicking off in the pot"). Although some hardeners tend to darken and stink of ammonia over time the marine epoxies I have used have essentially no shelf life. If the resin crystallizes it can be recovered in a warm water bath. Various additives and colorants can be mixed in to modify epoxy which makes it a versatile product. You can clean up fresh epoxy with vinegar, denatured alcohol or acetone. It does tend to soak into endgrain and darken joints with a visible "hard line". Epoxy bonds best to rough surfaces- smoothly machined joints, especially in dense hardwoods, should be abraded with 80# sandpaper.

I have used Titebond Extend a lot and like it. It has a very stiff cured glueline. It doesn't, though, give that much of an extended assembly time over Titebond l. I avoid Titebond ll Extend as the solids tend to settle out and require periodic remixing.

Urea modified hide glue does give a long assembly time and has the advantage of being repairable, sticking to itself and cleaning up easily with water. I have used only Franklin liquid hide glue which cures slowly with a rather flexible glueline. It is not at all water resistant.

All of these glues are strong enough if used properly. Prefinishing before assembly and using no more glue than necessary can help avoid staining problems.

[Tom M King]

Great post Kevin, but I pulled out this one quote to ask for a comment to see if you worded this as you intended.

" the marine epoxies I have used have essentially no shelf life"

[Kevin Jenness]

Great post Kevin, but I pulled out this one quote to ask for a comment to see if you worded this as you intended.

" the marine epoxies I have used have essentially no shelf life"

Yes, that has been my experience. I have used primarily West System 105/205-6 and Basic No Blush epoxy from Progressive Epoxy Formulators, and have kept them on the shelf for as much as 5 years. I've never had to discard any due to non-curing, although the West System hardeners get pretty dark red and funky.

https://www.westsystem.com/instructi...manufacturing.

[Maurice Mcmurry]

+1 for epoxy. I am most familiar with West System and Smiths. I almost always thicken the glue to paste consistency so glue is not running and dripping. I keep a log with notes on how many grams to mix for various applications. Tape is very helpful. Paste squeeze out can be lifted off with a putty knife and cleaned with denatured alcohol. West System and Gougeon Brothers have published extensively on using epoxy. Their publications are loaded with helpful information and techniques. Working with paste rather than liquid has been a game changer for me. A big thanks to the Gougeon Brothers for all of the educational material over the years.
I also keep liquid hide glue on hand. It is indispensable for things that need to be easily reversible.
I have never had problems with Titebond Extend and use it often.
I recently looked over some exterior doors that were glued with WeldWood Plastic Resin Glue 39 years ago and they still look excellent. I remember the door glue ups being messy.

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[andy bessette]

Great post Kevin, but I pulled out this one quote to ask for a comment to see if you worded this as you intended.

" the marine epoxies I have used have essentially no shelf life"

This. Good post. But say "indefinite shelf life".

I have been using WEST epoxy, for wood glue, virtually exclusively for nearly 50 years. Complicated glue-ups are no problem, as there is plenty of working time, as long as you select the correct hardener for ambient conditions (I generally use Fast Hardener).

First, prime all surfaces with neat epoxy mix; plywood edge grain usually requires many coats, wet on wet. If necessary, apply a glue coat of epoxy thickened using colloidal silica (sometimes with microfibers) or high density filler. ASAP remove squeeze-out using, first, a putty knife, then bits of paper towel soaked in acetone. If there is no squeeze-out, you didn't apply a sufficient amount of epoxy.

[Kevin Jenness]

I almost always thicken the glue to paste consistency so glue is not running and dripping... Working with paste rather than liquid has been a game changer for me... A big thanks to the Gougeon Brothers for all of the educational material over the years.

I will point out that West System generally recommends wetting out surfaces with unmodified mixed resin for best adhesion prior to adding thickeners to the mix. I'm sure single step bonding is adequate in most cases but there is some cost in strength. Personally I rarely use thickened epoxy for joinery. I do use thickeners when building up a surface to keep the mix from slumping or to make sanding easier. https://eu.westsystem.com/instructio...-and-clamping/

SINGLE-STEP EPOXY BONDING

Single-step bonding is applying the thickened epoxy directly to both bonding surfaces without first wetting out the surfaces with neat epoxy resin/hardener. We recommend that you thicken the epoxy no more than is necessary to bridge gaps in the joint (the thinner the mixture, the more it can penetrate the surface) and that you do not use this method for highly-loaded joints or for bonding end grain or other porous surfaces.

[Tom M King]

My experience as well, Andy. I haven't found an end to epoxy shelf life yet.

I'll ad another note about a cleaner. I had a boat business back in the 1980's where I sold boats and worked on them. One day one of the young guys working for me spilled some epoxy hardener on the concrete floor back in the shop. About that same time a salesman showed up at the door selling some new type of orange oil cleaner that he claimed would clean anything. It was a concentrate that he sold in gallons.

I told him that if it would get that epoxy hardener, which was a decent sized puddle, off the concrete floor that I would buy a case of it. He grew a big smile and ran back to his truck. It not only took the hardener right up, but cleaned the concrete floor down to look like it was finished last week and didn't take long to do it.

That case of gallons of that cleaner lasted me for a couple of decades. They sell similar things these days, but I've never seen the exact thing again. This stuff came out of Florida.

[Tom M King]

One question: What is neat epoxy resin hardener? I just don't understand what that means.

edited to add: As a correction to my earlier comment on epoxy, I should add a little clarification. Golf epoxy does have a shelf life of a few years. I don't know the differences other than it's engineered to break down at a temperature about a hundred degrees less than epoxy used in the making of composite golf shafts. It's probably heat that shortens its shelf life I expect.

[Kevin Jenness]

This. Good post. But say "indefinite shelf life".

Agreed. For my practical purposes there's not much difference. For highly stressed joints newer stock may be advisable. https://www.epoxyworks.com/index.php...ife-real-life/From the West System link in my earlier post, " We have mixed 15-year-old WEST SYSTEM 105 Epoxy resin with a newer hardener and it cured fine."

[Kevin Jenness]

One question: What is neat epoxy resin hardener? I just don't understand what that means.

It means mixed resin and hardener with no additives.

[Tom M King]

Thanks....

Another note for those new to epoxy: When even opening the top of colloidal silica thickener containers, wear breathing protection. The stuff is Very fine and floats in the air. You don't want to breathe it. When silica gets in your lungs, it doesn't ever come out.

[Michael Burnside]

I will add that when I use epoxy I mix in small batches. In small paper cups. It’s so easy to mix, takes 60 seconds to mix two part epoxy and I’m ready to go. It’s expensive so I don’t want to waste it but, again, goes a long way and since it has a longer open time when using medium/long hardeners, there is less stress making more.