How Strong Is Your Glue?

[David G]

I know this has been posted before, but it's always good to revisit - in case someone hasn't seen it, or has forgotten.

One key takeaway is that foaming polyurethane glue (like Gorilla Glue, or its imitators) is NOT a good choice in general. It does not fill gaps with strength, and even with good joinery, it's not very strong. Not covered in the article, but it also tends to contaminate adjacent surfaces worse than some of the others. I don't keep in in the shop at all.

Another reassuring bit, for me, was hide glue. I don't use it often, and I used to keep a whole 'hot-glue' setup on hand for those few times. Turns out the Liquid Hide Glue (Franklin makes the one I use) is just as good, if not better... and FAR more convenient. I went that route years ago, but it was nice to see my impression confirmed by the article.

Another interesting bit is that - where 'waterproof' isn't necessary, basic PVA is very good (Elmers or Titebond).

https://www.oldbrownglue.com/images/...urGlue_FWW.pdf

[John Meachen]

Its a shame you guys can't get good polyurethane glue.This old chestnut crops up with depressing regularity.I could show you a bare teak hatch that has been left outside year round since 1993 with no problem-it was glued with Balcotan which sadly is not sold here any more.

[Nicholas Carey]

Just gonna say...

- old brown glue makes liquid hide glue (they have a vested interest)

- polyurethane glues are fine. But they require s thin glue line and high clamping pressure. And they suffer, like many modern glues, from a repairability problem.

See our own Col. Bob Smalser's glue tests.

http://forum.woodenboat.com/showthre...st-And-Results

[StevenBauer]

Too bad they didn’t test one of the better polyurethanes like Pl Premium.

[sp_clark]

Too bad they didn’t test one of the better polyurethanes like Pl Premium.

Was that stuff available back then? I didn't discover it until about 2018 or later.

Henkel's MSDS for it's dated April 2019, probably a revision. Anyone knowing when the product first appeared?

[Breakaway]

Henkel's MSDS for it's dated April 2019, probably a revision. Anyone knowing when the product first appeared?

I used PL to in building a teak plywood bulkhead and solid timber companionway ( for a fiberglass boat) sometime in the late 1990s.

Kevin

[David G]

Just gonna say...

- old brown glue makes liquid hide glue (they have a vested interest)

- polyurethane glues are fine. But they require s thin glue line and high clamping pressure. And they suffer, like many modern glues, from a repairability problem.

See our own Col. Bob Smalser's glue tests.

http://forum.woodenboat.com/showthre...st-And-Results

OBG didn't do the testing, or write the article. It came from Fine Woodworking Magazine. Not surprising, though, that OBG would reprint it.

And, as the article states, the foaming polyurethanes are just not as strong - even when used correctly. 58% as strong as Titebond III (the benchmark).

[David G]

Too bad they didn’t test one of the better polyurethanes like Pl Premium.

Ideally... I have several other glues, and several other joint types and several other wood species I'd be curious about.

But I'm happy that they did the testing they did. I found it useful.

[David G]

Too bad they didn’t test one of the better polyurethanes like Pl Premium.

Ideally... I have several other glues, and several other joint types and several other wood species I'd be curious about.

But I'm happy that they did the testing they did. I found it useful.

[StevenBauer]

I used PL to in building a teak plywood bulkhead and solid timber companionway ( for a fiberglass boat) sometime in the late 1990s.

Kevin

PL is not a glue type. It is a brand name. They make dozens of kinds of glue. I’ve been using PL Premium Polyurethane construction adhesive for 10 or 15 years.

[Hugh Conway]

Just gonna say...

- old brown glue makes liquid hide glue (they have a vested interest)

that’s true, but they are also a small niche (a couple employees?) supplier that cares about a small niche market. As they progressively grow larger and focus on more industrial processes, the consumer focus dwindles in the glue industry. You pass by the people who make hide glue from scratch (only one in the us, like a dozen employees) followed by Franklin (400) followed by Hexion (4,000+ - Cascophen urea-formaldehyde - hard to find in small quantities, but a somewhat uniquely useful adhesive).

the advantage of hot hide glue is the pellets keep effectively forever and you can do a rubbed joint that will self stick, none of this pva floating

[BBSebens]

A Youtuber named James Wright did a substantial and thorough glue test recently. On his channel, Wood By Wright, he documented and scientifically tests dozens of different glues.

The results are surprising. Its worth the dive.

https://www.youtube.com/watch/ZoaTZY5cSQE

[bluedog225]

Good info. I was thinking about using some Gorilla glue recently. Thanks for posting David.

[David G]

A Youtuber named James Wright did a substantial and thorough glue test recently. On his channel, Wood By Wright, he documented and scientifically tests dozens of different glues.

The results are surprising. Its worth the dive.

https://www.youtube.com/watch/ZoaTZY5cSQE

Ben - I don't love that one. He doesn't have sufficient knowledge base to be evaluating. As a result - there's some accurate stuff in there, and some inaccurate. All in all... too much inaccurate or half-accurate. I'd steer folks away from it.

[BBSebens]

Im curious what you find inaccurate. I thought it was a very well thought out test, removing as many variables as possible.

[David G]

Im curious what you find inaccurate. I thought it was a very well thought out test, removing as many variables as possible.

Too much to type. If you're serious - give me a call, and we'll walk thru it. I think you've got my #, but if you need it, PM me.

[Breakaway]

PL is not a glue type. It is a brand name. They make dozens of kinds of glue. I’ve been using PL Premium Polyurethane construction adhesive for 10 or 15 year

SP Clarke asked for how long PL PU was available. I was just trying to provide a reference.

[John Meachen]

Could somebody explain why there is supposed to be any advantage in having a glue that is stronger than the wood being glued?I do understand about stress gradients but a lot of this stuff seems to be anxiety about not having the number one on the list.I also don't have too much concern about the repairability of a glue.If the item has held together for a good amount of time and the glue hasn't actually degraded-as old Cascamite is apt to do-then you do the repair and move on.Since I don't see the American brands,I will carry on using the glues I trust for the job I believe them to be best suited for.

[Jim Redding]

Whenever I hear anyone generally ragging on foaming polyurethane glue such as Gorilla Glue, I always feel called upon to put my oar in the water. I have made a fair amount of wood furniture and have considerable experience with gluing up various kinds of wood joints. I would never use Gorilla Glue for dovetail or mortise and tenon joints (just don’t do it). But for many years, Gorilla Glue has been my glue of choice for edge glued panels like table tops, floating door panels, etc. It is very easy to use in this application and in my experience works very well. I have never had a edge glued panel fail when using this glue. But the best thing about it and what keeps me coming back year after year is that the squeeze out, after it cures, is just light weight, brittle plastic foam that can be very easily scraped off with a card scraper. It is easy to get this squeeze out off well enough that it doesn’t leave a residue on the surface of the table top, etc. that shows when a clear finish is applied. This is a great advantage as anyone can attest who has ever glued up a table top with yellow glue, thought they had removed all the squeeze out only to have it show when they brushed on varnish.

[John Meachen]

I suspect that polyurethane,like PVA,comes in more than one variety.I had a conversation in the nineties with a man who was selling PVA and his company bought it by the tanker.He had a range to offer and some allowed longer open times and some cured at different rates.You just needed to explain your requirements and they would recommend the one that came closest to meeting those needs.I know that polyurethane foam for insulation comes in a range of densities and while I have never looked too closely at glue density,I have no qualms about using a glue that meets the D4 bonding requirements and as for joint pressure-plenty is all I ever use.

[MoePorter]

But the best thing about it and what keeps me coming back year after year is that the squeeze out, after it cures, is just light weight, brittle plastic foam that can be very easily scraped off with a card scraper. It is easy to get this squeeze out off well enough that it doesn’t leave a residue on the surface of the table top, etc. that shows when a clear finish is applied.

Jim"s observation is why I always have a small bottle of it around - that & it sets up pretty quick. I's a useful tool as long as you understand its limits...

[Paul356]

One problem with the you-tuber is that he apparently did not thicken the epoxy at all for the joints. especially when used for gap filling, epoxy needs to be thickened. that was a fault in the magazine article, too.

[peb]

One problem with the you-tuber is that he apparently did not thicken the epoxy at all for the joints. especially when used for gap filling, epoxy needs to be thickened. that was a fault in the magazine article, too.

That seems like quite a rookie mistake, makes one wonder about his other tests.

[Etdbob]

Interesting article.

Good to know the stuff I use is OK. My go-to boat glue is Titebond III, but I do use the Titebond II for a wide variety of non-boat stuff and have been very impressed with it over the years. So much so that I think it's fine for stuff inside a boat, at least.

Now I have used PL Premium 3x and 8x here and there -
I think it's fine construction adhesive, and sometimes the gap filling bit is quite useful. I used some on a nice five foot by three foot gate I just built for a customer.
Not a single metal fastener in it, all inletted and glued. Mostly with Titebond II, but those pesky corners got PL stuff.
Not proud of the corners but it looked fine painted, ( made it out of the worst stock I had on hand, that would have went into the shop stove otherwise!), the gate was free - It was a condition to get a much larger construction job for this feller.

I kind of doubt the longevity of PL Premium. Ten years from now I'm not sure it will still be holding.

[John Husky]

The lesson from this test should be that improper use is pilot error. Every instance of glue joint failure is a mistake. Gorilla Glue and similar foaming PU glues don’t create a strong gap filling joint. This should be obvious, and I can’t believe they advertise it as such.Used properly, it’s plenty strong. Epoxy when used incorrectly in a gap filling joint, or a tight joint for that matter, will fail too. Follow the directions. I only use epoxy when I need gap filling properties, and I mostly stick with Titebond II and III otherwise (sorry, pun). I’m interested in learning more about PL Premium and the best use of Gorilla Glue. The solvent clean up is kind of a turn off.

[Edward Pearson]

Durability studies rank resorcinol (when it can be used) better than epoxy which is superior to polyurethane.

They have near equal strength at the start but decay differently.

Wood can be more flexible than the glue so cyclical loading studies of durability are relavent for the life of a boat depending on the application, besides the initial strength.

[Hugh Conway]

Not every glue joint failure is a mistake. For some applications (not marine, likely) it’s better to have the joint fail leaving pieces readily reassemble than to have a shattered mess.