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Reading Is glue the best permanent join? and How can I join two boards at the ends? it sounds like the consensus is that gluing end-grain just doesn't work well. As this answer explained,

When glue is applied to end-grain, the grain acts as little straws and draws a lot of the glue up the wood, away from the joint (similar to how the grain draws water up the tree when the tree is alive). In these cases, the majority of the glue is pulled away from the joint and (without more elaborate joinery techniques) a strong joint cannot be achieved, no matter how rough you sand or how tight your clamps are.

Is this true for all glues – even epoxy and CYA?

It seems like there should be a way to seal the end-grain to prevent it from (excessively) drawing in glue, while still preserving the surface area and characteristics that allow wood glues to work effectively. Are there no established processes for that?

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  • This is the reason the art of joinery exists.
    – DGM
    Apr 10 '15 at 0:02
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Update, 2021

The picture appears now to be a little more complex than previously supposed, see update to other Answer in What are the different grain directions, and how do they affect joint strength? and the Comments that follow.

In practice end-grain glue joints are typically weak for various reasons discussed in the follow-ons to that iconic video. Even in a low-stress use like a smallish picture frame it is still advisable to ensure your mitres are pretty much perfect, you glue and clamp with particular care. And by all means reinforce the joint if you want to future-proof it against unexpected strain.

Various reinforcement methods are available for mitres, the simplest (e.g. nailing or pegging) take almost no extra time, and some of the more involved ones (e.g. keys) look good while adding lots of strength.


it sounds like the consensus is that gluing end-grain just doesn't work well.

It has long been acknowledged to be the weakest joint. However, that doesn't mean you can't or shouldn't do it, ever.

The issue is actually whether it's strong enough, not strong per se. In a picture frame for example a simple glued mitre is not considered strong enough, and for good reason because the mitre would be the only joint responsible for holding the piece together, the glue surface area is small and the combined weight of picture, matt and glass can be considerable. And note the orientation of the joint faces to the load — pulling it directly apart. Failure in this situation could be considered likely, not just possible.

But if the mitre is at right angles to the load, and the weight it must bear is small (e.g. the weight of just the pieces of wood themselves, as in a crown moulding), then a simple glued mitre could easily be sufficient.

To be honest though, given how easy it is to reinforce the mitre, even a single staple across the joint adds a lot of strength, it hardly seems worth taking the chance that it might separate on its own. I should also mention corrugated fasteners here, although they're looked down upon by many woodworkers as being crude they should be considered for this as they stabilise the joint immensely.

Is this true for all glues – even epoxy and CYA?

Mostly yes.

CA/superglue is a particularly poor woodworking adhesive anyway as it is too brittle to deal with movement, and it's poorly suited to highly-absorbent materials which of course end grain is (neither of which stop it being sold for this purpose).

Epoxy on the other hand is a much stronger class of adhesive and it deals better with unusual surfaces or textures. To glue end grain best with epoxy you would want to pre-wet both joint faces with the adhesive and then apply additional glue to the surface before bringing the pieces together. There is a problem however, as strong as epoxy is it is not a good thin-film adhesive (thin like woodworkers want, nearly invisible) which is why you don't want to use very firm clamp pressure with epoxies. So to be at maximum strength the mitre joint would end up quite visible.

It seems like there should be a way to seal the end-grain to prevent it from (excessively) drawing in glue, while still preserving the surface area and characteristics that allow wood glues to work effectively. Are there no established processes for that?

The absorbency of the end grain was identified by craftsmen as the problem and sealing of the end grain prior to final glueing to fix it was theorised a long time back, possibly before the 19th century. Certainly by then there was mention in woodworking handbooks of 'sizing' the end grain (painting with thinned glue) prior to application of the full-strength adhesive to the mitre and then bringing the joint together. Done correctly this does create a far stronger union between the mitred pieces than otherwise, but even with that it is not as strong a joint as is sometimes desirable. Bear in mind the context here: the strength of other joints in woodworking is as strong as the material itself, which is quite a high standard to meet.

Using modern PVA-type woodworking adhesives if you want to avoid using any kind of additional reinforcement then this is the method to adopt. In bullet points for clarity:

  • The glue for sizing is normally slightly thinned; by how much is open to debate, but it seems likely the absorbency of the wood species should be the deciding factor.
  • The size is painted on the end grain and left to partially dry.
  • Application of full-strength glue and clamping.

The drying time for the sizing may be anywhere from 15 minutes to an hour, depending on wood species, the glue used and local conditions (temperature and relative humidity).

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  • What is used to thin the glue like you mention here?
    – lnafziger
    Dec 14 '20 at 22:37
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    @lnafziger. PVA-type adhesives are waterbased, so water.
    – Graphus
    Dec 15 '20 at 9:14
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I have read that some will prep the end grain with a pre-glue job. apply some glue to the end grain and let it dry, then actually do the glue up job.

However, you still have the issue that the structure of end grain is not an ideal surface for glue. I never leave a corner as a glue only joint. There are many different kinds of joinery out there to strengthen the joints and I always try to use one of them.

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Look at Patrick Sullivan's "end grain glue" video experiment on YouTube to be amazed by his analysis showing that end-grain glue joints are actually stronger than other grain orientations that have the same amount of bonded surface area. The reason that end-grain joints are dismissed is because the joint is usually small when separate end-grain surfaces need to be attached. In addition, with end-grain joints, the orientation of the grain in the wood makes it much stronger than the glue, whereas in other grain orientations, there are portions of the wood that are weaker than the glue. https://youtu.be/m7HxBa9WVis

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  • 2
    You may as well refer to all the follow-on videos as well that add to the story, which is not at all surprising. It is rarely the glue (in a good joint) that fails, but rather the wood around it. The nature of the break isn't all that useful, actually. For example, no one is going to change when and how they make mitres -- they are strong enough. And tradespeople aren't going to start end-gluing boards to make them longer. It isn't the strength of that glue line that determines how dimension lumber will be used. Practical woodworking doesn't really change as a result of this lab work.
    – jdv
    Oct 12 at 12:21
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    This link was posted here recently. I watched the video and was amazed both at how good the results were and how this just hadn't occurred to anyone before. However, one thought was nagging at me throughout the whole video- "when in the world will I ever be able to apply this knowledge?" About the only time would be to make butt joints instead of mitered joints, and that's only because I'm not yet good at cutting miters - they look much better IMHO than a butt joint.
    – FreeMan
    Oct 12 at 16:47
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Another consequence of the structure of wood is that those little straws don't have as much surface area for glue to adhere to as with side grain.

There are 'pore fillers' that will help even out the blotchiness of staining woods, and they can be used on end grain. I'm not sure if anyone has experimented whether or not they affect an end-grain glue joint though.

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Your result will never be as good as cross grain on cross grain. TiteBond manufactures a thick and long working time glue designed for end grain called "No Run, No Drip Wood Glue." Link to website I've used this before and I've been pleased with the results.

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