# OUTSTANDING video on end grain gluing



## phinds (Oct 10, 2021)

I thought about putting this in the general discussion forum but it actually IS about wood characteristics and in any case, I consider this a must-watch video for all woodworkers.

Turns out end grain gluing is the STRONGEST type of gluing as opposed to side to side and side to end. He shows this with a very careful, formal, analysis with about 6 kinds of common woods using a force gauge.






AND he doesn't even mention the fact that you can increase the strength of an end-to-end glue joint by smoothing down both surfaces first.

Another point to be made about titebond type glues is that it shrinks a bit as it dries so that for very porous woods such as oak, end to end joints can be made the strongest, if you don't mind spending the time on it, by first putting on a layer of glue, letting it seep into the pores, and then wiping it off from the surface and then when it has dried, smoothing the surfaces. This give a larger glue area because now the dried glue in the pores presents a flat surface rather than a hole (or at least, mostly flat, since the original application will have some shrinkage and part of the pore may still show as open).

*EDIT: by the way, it's very important to be clear about what this does NOT show* and that is the fact that leverage can be a huge factor in joint failure and end to end is NOT usually good joinery in real-world applications. For example, take the end to end joint that IS stronger than a side to side joint. Those two pieces that took so much force to break, could be broken over your knee with not too much effort if each of the pieces had been a couple of feet long instead of a few inches. It would be the difference between putting your thumbs on the joint and pushing and pulling the edges with your fingers (not at all likely to break the joint) vs pushing the joint with your knee and pulling much father out with your arms (VERY likely to break the joint). So even when end to end is the strongest pure glue joint, pure glue joints are often a bad idea.

Reactions: Like 1 | Way Cool 1 | Informative 2


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## JerseyHighlander (Oct 10, 2021)

That was highly interesting on many levels and I love the apparatus and instrumentation.
All kinds of thoughts going through my head but keeping strictly to the topic, my most notable argument to the presentation is that it shows the opposite, that end to end glue joints are weaker or maybe it was inconclusive due to design considerations. Yes, it did take higher pressures to cause failure in the end to end joints but it was the "glued joint" specifically that actually failed, not the wood. In all the side to side and side to end joints, they may have failed at a lower pressure by the instrumental readings but, it was never the actual glue joint that failed, always the wood. The end to end joint was pushed to failure because of the inherent strength of specific grain orientations. Yes, I know, I'm stating the obvious but this is where semantics actually matters.

Still all very interesting and useful information. Thanks for posting that.


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## phinds (Oct 10, 2021)

JerseyHighlander said:


> Yes, it did take higher pressures to cause failure in the end to end joints but it was the "glued joint" specifically that actually failed, not the wood.


And your point is??? He makes it clear that he's NOT saying that glue is stronger than wood fiber, just that glue is stronger than lignum, so end to end gluing is clearly superior to end to side or side to side but certainly not stronger than long grain wood. You are just supporting his discussion. There is no semantics involved.


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## JerseyHighlander (Oct 10, 2021)

phinds said:


> And your point is??? He makes it clear that he's NOT saying that glue is stronger than wood fiber, just that glue is stronger than lignum, so end to end gluing is clearly superior to end to side or side to side but certainly not stronger than long grain wood. You are just supporting his discussion. There is no semantics involved.


I guess I'm saying that the actual "glued joint" was never tested to failure on any but the end to end joints so we can't know how strong that joint is ultimately, only that it is stronger than the wood grain, when stressed in a specific orientation.


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## phinds (Oct 10, 2021)

JerseyHighlander said:


> I'm saying that the actual "glued joint" was never tested to failure on any but the end to end joints


Did you watch the video? He specifically tested end to side and side to side. The glued joint held in both cases and the wood failed. How is that not testing the glue joint?


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## JerseyHighlander (Oct 10, 2021)

phinds said:


> Did you watch the video? He specifically tested end to side and side to side. The glued joint held in both cases and the wood failed. How is that not testing the glue joint?


I did watch the video, obviously. Once again, that glue joint, the joint made with glue, between the two separate pieces of wood, was never pushed to the point of failure. I realize, it obvious, it couldn't be within the design parameters of his test, due to the limitations of the wood in specific grain orientations. Nothing new under the sun here. 
Starting to feel as though discussion is going in a bad direction here. Not constructive. Delete all my comments if you wish, I pretend I didn't open this thread.


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## phinds (Oct 10, 2021)

JerseyHighlander said:


> I did watch the video, obviously. Once again, that glue joint, the joint made with glue, between the two separate pieces of wood, was never pushed to the point of failure. I realize, it obvious, it couldn't be within the design parameters of his test, due to the limitations of the wood in specific grain orientations. Nothing new under the sun here.
> Starting to feel as though discussion is going in a bad direction here. Not constructive. Delete all my comments if you wish, I pretend I didn't open this thread.


I think I get what you mean, it just seems a strange way to look at it, but then I've been accused of being a bit strange myself

Reactions: Funny 1


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## phinds (Oct 10, 2021)

JerseyHighlander said:


> Once again, that glue joint, the joint made with glue, between the two separate pieces of wood, was never pushed to the point of failure.


But it WAS pushed to the point of failure, it just didn't fail before the wood did which was the whole point of the video. Again, I think I sort of see what you mean, but just find it an odd way of looking at it.


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## Karl_TN (Oct 10, 2021)

What I primarily got from this video is that wood glue is the weakest part of an end grain to end grain joint, and that wood glue on a side grain joint is stronger than the lignun holding the fibers together. Also, an board with wood fibers along the grain are stronger than a flat glue joint. In other words, I wouldn’t walk across a bridge that depended on either flat glue joint for supporting my weight. Let me ask it this way, how would this information in this video change the way you do wood working?


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## phinds (Oct 10, 2021)

Karl_TN said:


> how would this information in this video change the way you do wood working?


It would make me much less hesitant to do end to end gluing for short runs where there isn't going to be much leverage against the joint. Previously I would have worried about an end to end joint practically just falling apart.

For structural joints I would continue to use joinery since, as I said in at the end of the post, pure glue joints are NOT a substitute for joinery.

Reactions: Like 1


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## jasonb (Oct 10, 2021)

Thanks for sharing. I found that very interesting. And who knew.... I sure had no idea.

Reactions: Agree 1


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## Karl_TN (Oct 10, 2021)

phinds said:


> It would make me much less hesitant to do end to end gluing for short runs where there isn't going to be much leverage against the joint. Previously I would have worried about an end to end joint practically just falling apart.


What came to mind was maybe cutting boards and segmented turnings, but I’m having a hard time imagining other places that I’d use end grain to end grain glue up. Probably due to my lack of imagination. Curious what other short run items might you be thinking of here? Also, what would you have done differently, if anything, with this Youtuber‘s experiment?


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## phinds (Oct 10, 2021)

Karl_TN said:


> What came to mind was maybe cutting boards and segmented turnings, but I’m having a hard time imagining other places that I’d use end grain to end grain glue up. Probably due to my lack of imagination. Curious what other short run items might you be thinking of here? Also, what would you have done differently, if anything, with this Youtuber‘s experiment?


One place were I would have used end to end glue joint was in some drawer bottoms that I needed quickly and could only finish all of by using shorter pieces and lap joints. Turns out the lap joints weren't necessary.


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## wombat (Oct 10, 2021)

Interesting video. A few points come to mind. First I sympathize with what Jersey was trying to say about the end grain glue failing. He was bending wood along the strongest part of a board, i.e. along the long grain. Whereas the other two scenarios had an inherent weak spot in the wood. 
I'll admit it's a tricky one. 

My biggest complaint is that all his testing was done "slow and steady". I can almost guaranty that if they were shock tested, the end grain would lose by a big margin.

Thirdly, I think I've tried most glues out there and the Titebond is far superior to anything I've tried, so I'm not surprised it did so well in the end grain test. 

On a side note. How to test wood grain when you don't have a lot of expensive equipment. Long grain testing and Cross grain testing

Reactions: Like 1


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## phinds (Oct 11, 2021)

wombat said:


> My biggest complaint is that all his testing was done "slow and steady". I can almost guaranty that if they were shock tested, the end grain would lose by a big margin.


That's a good point. No idea if you are right but it certainly would be a good test to run. On the other hand, it hardly matters in real life since in any situation where significant shock is likely, pure glue joints are likely to be a terrible idea compared to almost any kind of actual joinery.


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## Nature Man (Oct 11, 2021)

Fascinating scientific study. It appeared to be under a very controlled environment. He did not mention moisture content of the wood he used in the experiments, unless I missed it. The study measured breakage only in one plane, so further study is probably needed. Chuck


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## phinds (Oct 11, 2021)

Nature Man said:


> Fascinating scientific study. It appeared to be under a very controlled environment. He did not mention moisture content of the wood he used in the experiments, unless I missed it. The study measured breakage only in one plane, so further study is probably needed. Chuck


All true but I think you're overthinking it. Hey ... that's MY job !


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## phinds (Oct 11, 2021)

wombat said:


> Thirdly, I think I've tried most glues out there and the Titebond is far superior to anything I've tried, so I'm not surprised it did so well in the end grain test.


I've never done any comparison so @wombat have you tested Titebond against CA glues? I've just started using CA glue and still wonder about it.

Reactions: Like 1


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## Nature Man (Oct 11, 2021)

phinds said:


> All true but I think you're overthinking it. Hey ... that's MY job !


I tend to do that! I’ll gladly defer…. Chuck


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## wombat (Oct 11, 2021)

phinds said:


> I've never done any comparison so @wombat have you tested Titebond against CA glues? I've just started using CA glue and still wonder about it.


I've never had much luck with CA as a glue, it makes a nice gap filler, but that's as far as I trust it.

Reactions: Informative 1


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## barry richardson (Oct 11, 2021)

Interesting info, and well documented, but I cant see that it will cause me to do any thing different woodworking wise. An endgrain to endgrain or to sidegrain joint might be stronger initially, but over time it will fail much more. he didn't take into account environmental effects down the road like humidity fluctuations which side to sidegrain handles better. Carpenters and woodworkers figured this out a long time ago. So it is still a rookie mistake IMO. BTW, CA is not a very good glue for general woodworking because it cures to almost glass like hardness, and cant move with the wood, so it fails....

Reactions: Like 1


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