The Secret To Miters That Never Crack!(Wood Glue VS CA Glue) 

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That's a very interesting point. I remember testing this out with my Dad 20 years ago....I think the Dap caulking was stronger than wood glue, but I'm not 100%. That could make for another interesting video.

I have seen other yt videos say the glue is stronger but dries rigid. So impacts or stress over time makes it more brittle compared to dapp, which dries with more elaciticity so can handle impacts, stress, and shocks better in the long run.

The point of this video was not to prove that CA is stronger than wood glue. The point was to prove that wood glue does not have a strength advantage in miters, so there isn't any reason to use wood glue instead of no-clamp no-wait CA.

@@SplashJohn I'd be curious about how well CA lasts over time compared to wood glue. The conventional wisdom is that CA fails pretty quickly, but it'd be interesting to see whether that's actually true or not (in theory, humidity and vibration both fatigue CA a lot more than wood glue, but testing would prove/disprove).

​@@SplashJohn Theres a huge reason to use wood glue. When you get some squeeze out you can take your palm sander and sand the miter, creating sawdust and it will bind with the glue to fill the miter 110%.

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I was thinking the same... he didn't use much clamping pressure

Interestingly enough, I just watched this exact test recently, and the result was the exact opposite. (video title you are clamping too long, by woodcraft by suman). For extreme amounts of clamp time, you did get marginally better performance, but for most practical applications of a tight fitting joint, not clamping at all performed better (for example, 12 hours clamped is worse than 24 hours never clamped, and 30 minutes clamped and then 24 hours after the clamps were removed was MUCH worse than 24 hours never clamped. What wood glue requires are two things: a tight fitting joint, and to not be disturbed after assembly. It can still muster a high strength joint without clamps, and in fact, if you clamp it for only half an hour and then remove the clamps, the joint gets WEAKER, than if you had never used clamps at all. (for a tight fitting joint, to be clear. I don't know of any way to really measure performance of bad joinery). Tellingly, Titebond (original)'s own instructions state that you need "enough pressure to bring joints tightly together". It has some numbers afterwards, but the first sentence makes it clear, if the joint is tightly together, the glue is working, and that is definitely what I have observed, as we do a lot of wood glue on outside miters for baseboard. They do hold together, as long as you don't have any springing open after you apply glue. (not a tight fitting joint). Wood glue is commonly used without clamps, and it performs fine. Frankly, though, I don't really see this test as super relevant. The way we install casing, we nail immediately on both sides of the corner, so the nails are holding the corner to probably a single piece of material, be that a stud, a jamb, or even some drywall. Even if the house DOES shift, the joint only gets stressed if material on either side of the joint are being moved relative to each other, which is very difficult when then joint is nailed directly to a single 2 inch wide piece of material. That 2 inch piece is unlikely to expand, contract, or shear itself very much. Also, at work, we use both wood glue and CA glue, without issues. Strength isn't really the issue in professional finish carpentry, CONSISTENCY is. It's never about how good is your average joint, it's about how good is the absolute worst joint. Consistency of performance is the key, which is why we love CA so much. Because you CAN disturb the joint immediately after use, it is not vulnerable to mishap, or interference of other trades. Wood glue can be.

Mathias Wandell did a video years ago testing wood glue and the pieces he used less clamp pressure held better.

Thats why I use wood glue and CA with activator together, the wood is for strength the CA to act as clamp.

Penetration is not your friend with CA glue - its bond is all at the surface layer. Penetration can drive all the glue into the wood and leave little for the joint.

@@connecticutaggie If all the glue penetrates sure, I agree. If only some of it penetrates, I'd argue that it makes the bond stronger. We can see this in manufactured goods like MDF, where there is no surface glue, it's all penetrated into the fibers. Another example are laminates like fiberglass and carbon fiber.

Interior absolutely, ai personally use wood glue for strength but CA to act as a clamp holding pieces in place while wood glue sets up

Slow down sparky. A home that might settle or have seasonal expansion and shrinkage making forces that aren’t linear!!?? Like one commented, TORQUE. Pressure or weight test is a test tube scenario and pretty much useless for a living structure that breathes and is connected to air, all the elementals lol sacré bleu!! Whoever uses the most flexible caulking has the greatest efficiency I would think. One commenter uses screws tho that also would be superior

If I use CA glue, then nail the top piece while securing the vertical pieces in a way that can move slightly, then, never crack.

Not relative to the cost of a professional's time. You can case probably about 3000-4000 square feet of house with a 100g bottle. That's about 25 dollars. It isn't free, but it's a pretty crazy place to try to save 25 bucks. also, you can just buy bulk CA. I don't, because my CA is employer provided, but it is freely available in my area in 8 ounce bottles, and it would only take you a couple minutes to find a 16 ounce bottle supplier online. By that point, you are getting glue at.... about 12 dollars per 100g bottle.

@@timmietimmins3780 Agreed, price of CA is inconsequential to a professional, or to anybody who values their time over about $5 an hour.

That's cool, like I said I've never tried it. Those bottles just look really little but they obviously do more than I would have guessed. 👍

Interesting idea.

Doors slamming and seasonal shifting along with the expansion and contraction of wood

@@TheFunnyCarpenter ah, makes sense

Sounds like a plan

But you don't want the flexibility in this case, you want the glue to not allow any movement.

Some excellent points here mate! I did consider adding biscuits into the equation, but ended up thinking it's a very unrealistic option for most people. I'd also say with the CA glue result can definitely vary depending on how you put them together! Cheers.

@@TheFunnyCarpenter It's certainly fair that biscuits are not available to everyone, especially in a YT audience. And I think they are a big factor in my results, just in the surface area of glue. And it would be stupid expensive to use CA for the amount of glue needed with biscuits.

thanks for the info

That's a good point. I have some reference in the fact I live in a house that I used the CA glue method. 18 months later still no cracks. I do have some sample trims I glued up a year ago, maybe I will make another vid and test this out.

It works but only if there is good tight contact between the surfaces and clamped well with nails. Any error in those and it’s weak

The nails likely won't stop it from cracking, and the corner clamp and stretched out tape are going to give you better initial glue up contact.

Thanks man ! Let's hope for the best 1930's house are full of surprise. Worst case I have your videos on how to fix it ;)

Cheers Maria:)

I've tested a bunch of variations of how to use CA glue for miters- what's shown in the video is the best method(my opinion). It's both strong and highly practical for high production work.

@@TheFunnyCarpenter high production being the key here, are you making videos for them or for home DIY people that want to spend a bit more time and a few more bucks to make things that last 30 to 50 years or more?

@@Ethan7s If your goal is to make something that will last 30 to 50 years, why are you watching a video about glueing up MDF and pine?

@@SplashJohnunsubbed

Haven't been watching actual finish carpenter videos then as they use CA glue first and foremost because of the speed. As for the thermal shrinking, the CA glue still stops it from cracking as, at least with mdf, it creates a bond that is as strong as the rest of the material. So it may want to shrink a bit when humidity is low but can't.

@@curtisbme Right, right, then.. Got a link to a video that shows the effect over time? Or one that shows edge trim that genuinely carries 45 lbs? Either of which would actually address my comment.

@@marsrevolutionary Your 45lb comment means nothing. How it breaks is relevant though as it shows that the material is breaking, not the glue. As for showing that CA on MDF stops cracking at the joints and is much faster, if you have ever done trim work you would have all the evidence you need. I'm not going to bother to do the searches for you as you aren't actually interested in the information, just doubling down on your incorrect statement that there are no videos about it saving time or that it isn't going to stop cracking because of humidity.