Domino glue up problem

[luvmytoolz]

I read somewhere, might have been on the FOG, that applying PVA type glue to both surfaces makes sure both surfaces are "wet".  Apparently you can end up with the glue being sucked into the pores of the wood and get a dry joint.  For panel glue ups (and I've not done that many) I apply glue everywhere!  Both surfaces and into the domino mortise.  I use a small plastic spreader to distribute the glue in the mortise slot.

Bob

That was my observation from the timbermill I worked at when we laminated beams as a teenager, applying to one face only the glue can "skin" over before everything was clamped up, effectively creating a somewhat dry joint, definitely weaker. We ended up going to a resorcinol resin that we slathered on. Whether right or wrong, I must admit I cringe when I see on social media cuttingboards having glue applied to one face and then the pieces are flipped and clamped.

 

[Cheese]

Cheese, your research project is pretty fascinating.

How long did you let the joint set before you broke it apart? The bond between the end grain and face grain is what makes me ask. It's what I would expect to see on a relatively new assembly. As I understand it, failures between end-grain and long-grain joints happen after the joint goes through a couple seasonal cycles. The long-grain moves and the end-grain doesn't and the bond breaks down.

The stock adhered to the Domino and ripped out of the mortise is reassuring. Gives me confidence in all the stuff I've built with Dominos.

Jeff, I let the joint set up for a couple of days before I attacked it with a hammer.  [big grin]

That seasonal cycle thing makes sense because frankly, I was surprised at the strength of the bond between the long grain & end grain after a couple of days.

I've also done the glue sizing thing mentioned by waho6o9 and that also works well. It usually needs 2 coats because the 1st coat just gets sucked up completely.

 

[jeffinsgf]

Yeah, some "influencer" did a video a couple years ago where he declared that everything we've known for a couple thousand years about joinery is complete bunk, because he glued face grain to end grain and it was just as strong as face grain to face grain. But it was the same as your test (except without the Dominos, which makes it an actual joint). A couple days to cure and then judgement day.

I don't think he would have seen the same results if he had left the joints alone for a year.

 

[Packard]

I’m late to this conversation and I only scanned the earlier posts.  If this question has been asked and answered, just kick me out of the conversation.

Question:  After jointing the edges and before cutting the mortises, did you check the fit?

I don’t do much of this type of work.  When I do, I lightly fasten two boards side by side with a few light dabs of hot glue.  Then I set the fence on my table saw so that the blade removes approximately the same amount of material on the right side of the blade as it removes from the left side of the blade.  Usually that make a glueable joint. 

I’m not sure that this is translatable to working with a track saw.

But back to the question:  Did you check the fit before any Domino work?

 

[ChuckM]

Sizing, applying glue to end grain to be absorbed first and letting dry, and then doing your glue up isn't done much
these days because of time constraints.

I do when I make mitered frames or trays.

 

[Packard]

I also glue everything in sight... [big grin]...what really helped me with glue-ups is when I started to use flux brushes to apply the glue. The flux brush lays down a nice consistent layer of glue and it applies that evenly over the entire surface. No more massive amounts of glue squeeze-out or hydraulic lock to contend with.

Like Birdhunter, I also only glue up one joint at a time. That gives me time to wipe off any extra glue around the Domino tenon body and the edge of the board with a damp rag.

Here's a joint I constructed from fir 8 years ago that I intended to break apart to monitor how evenly/unevenly the glue was applied with a flux brush and to see what parts adhered to each other and how strong the adherence was.

Photo 1: Interesting to note that despite the end grain/long grain bond, the end grain still retained/removed quite a bit of the long grain from the other board...it's only the very small areas with the red arrows where there was no end grain adhesion.
The yellow arrows highlight how uniform the glue coverage is when using a flux brush...no hydraulic lock here.  [smile]

Photo 2: Look at the long grain of the Domino and notice it's removed wood fibers from inside the mortise. If you need or want some extra strength within the joint, don't be afraid to glue the Domino, it can be used for more than just aligning boards together.

Photo 3: Notice all of the long grain fibers that were ripped out and are permanently attached to the end grain. Also note that to break this joint apart, I had to break the mortises open because of the long grain-to-long grain bond between the Domino and the mortise.

[attachimg=1]

[attachimg=2]

[attachimg=3]

I too use flux brushes.  I get them from Harbor Fright for $3.00 for 36 brushes.  I treat them as disposables.
https://www.harborfreight.com/12-in-horsehair-bristle-acid-shop-brushes-36-piece-61880.html

 

[Crazyraceguy]

I too use flux brushes.  I get them from Harbor Fright for $3.00 for 36 brushes.  I treat them as disposables.

I do pretty much the same thing, Amazon by the gross, for $15-$16. (at least the last time I got some)
I also use the cheap 1" chip brushes, for bigger surfaces, until it gets big enough to use a spreader. At that point, a little rectangle of laminate the size of an index card, covers large areas very quickly. It's just as disposable too, and 100% free. I drop the wet end of a brush in a cup of water, to keep it moist, as I am working with it. Sometimes I just leave them there, at the ready.
Glue is fairly subjective, even to the point of which type for which job. I use TiteBond2 most of the time, but Melamine glue comes in too, as well as a quicker drying "white" glue that is formulated for dowel assembly.