Polyurethane Glue and Domino Joinery

[Michael Kellough]

Never tried chilling the glue but wouldn’t the increase in viscosity be a drag?

 

[TSO_Products]

You are suggesting that filling the slot at the ends of the domino will add strength?

I don’t see how it would.  And of that gap were filled with glue, the PU would try to force the domino out of the slot making new demands on clamping.

Has anyone ever done testing on dominoes, dowels or tenons suggesting that PU offers greater strength than other glues?

If that gap causes weakness, then I should drill shallower holes for my dowels.  I always leave about 1/8th of an inch gap at both ends of the dowels.

I suppose I should have said edges rather than ends. I am talking about the rounded edges of the mortise and the rounded edges of the Dominos not fitting tightly to each other. I think, with no empirical evidence, that polyurethane glue makes a better joint than PVA, and even if it is only as good... it is faster to spread, clamp and clean up.

I will agree that cleaning it off your hands is impossible. That's why I use gloves.

[member=7266]jeffinsgf[/member]  - interesting topic - I wonder what actual problem led you to consider gap filling adhesive. Did you have some failures or did you see test results pointing to a weak and deficient joint? - any unusual requirements associated with your project?

Hans

 

[jeffinsgf]

[member=7266]jeffinsgf[/member]  - interesting topic - I wonder what actual problem led you to consider gap filling adhesive. Did you have some failures or did you see test results pointing to a weak and deficient joint? - any unusual requirements associated with your project?

Hans

What failures I've had (which are very, very few) have been associated with trying to get away with only spreading glue on the mortise. As long as I spread on both the mortise and the Domino, I've had zero failures in hundreds of Domino joints.

On a recent project that had a fairly complicated assembly I decided to use Gorilla Glue and dampen the Dominos to speed up the glue spreading. Turned out that in my "design on the fly" process I made a rather large math error and had to cut a couple joints apart and shorten up the legs. The cut apart joints looked amazingly tight. The glue had expanded into every crevice on the round ends of the Dominos and unlike the foamy look of what oozes out on the surface, the glue was rather dense and hard.

I also have an outdoor table glued together with Gorilla Glue that has 5 Northeast Ohio winters under its belt and all the joinery is as tight as the day I took the clamps off.

Just seems like a good choice for Domino joinery to me. YMMV

 

[Packard]

Dowels, biscuits, and I assume dominoes also, depend upon moisture to swell the components for a really tight fit.  Water-based glues provide that moisture.  I’m pretty sure that Gorilla glue is not water based.

So I wonder how much strength is sacrificed by giving up on the swelling of the dominoes that is lost by not using a water based glue.

 

[rst]

Polyurethanes not only do not swell but need moisture to cure.

 

[jeffinsgf]

Dowels, biscuits, and I assume dominoes also, depend upon moisture to swell the components for a really tight fit.  Water-based glues provide that moisture.  I’m pretty sure that Gorilla glue is not water based.

So I wonder how much strength is sacrificed by giving up on the swelling of the dominoes that is lost by not using a water based glue.

Poly needs moisture to cure...hence the recommendation to moisten at least one side of the joint. I thoroughly moistened the Dominos before inserting them. I'm pretty sure they expanded just as much as they would have with PVA.

 

[Packard]

I recall the advice to “paint the joint with water” prior to using Gorilla glue.  And like you said, for curing. 

I don’t think we have much more than opinions on the topic.  I wish there was some actual data to hang our hats on. 

I did test the strength of different types of glue, specifically Corner Weld, a glue designed for the picture framing industry and largely replaced the white glue (Elmer’s) that was in wide use at the time.  I tested that, and there was no comparison.  The Corner Weld was vastly stronger.  They advertised it as being engineered for “end grain to end grain” adhesion.

I re-tested that 30 years later and compared it with Woodworker’s III.  I only tested three samples of each on end grain to end grain and they performed almost identically. 

The big difference was that Corner Weld has extremely short open times, and will tack up in 30 seconds to a minute.  Which is OK for the picture framing industry, but is a problem for almost everyone else.

If I were still in the framing business, I would switch to Corner Weld (my current glue is Woodworker’s III).

 

[TSO_Products]

Dowels, biscuits, and I assume dominoes also, depend upon moisture to swell the components for a really tight fit.  Water-based glues provide that moisture.  I’m pretty sure that Gorilla glue is not water based.

So I wonder how much strength is sacrificed by giving up on the swelling of the dominoes that is lost by not using a water based glue.

Poly needs moisture to cure...hence the recommendation to moisten at least one side of the joint. I thoroughly moistened the Dominos before inserting them. I'm pretty sure they expanded just as much as they would have with PVA.

[member=7266]jeffinsgf[/member]  - If your looking at other high strength adhesive options, RESORCINOL can provide extremely strong connections PROVIDED the joint is close fitting. You might find it interesting from a strength standpoint. A two component systems (powder and liquid). can be used with heating during the assembly to speed up cure time. Open time is not unusually long at room temp. It is not designed to be gap filling - just ulra high strength structural wood connections. Unlike Epoxy, it is not affected by heat or sunlight UV exposure. Available through industrial supply sources only in my experience.

Hans

 

[luvmytoolz]

[member=7266]jeffinsgf[/member]  - If your looking at other high strength adhesive options, RESORCINOL can provide extremely strong connections PROVIDED the joint is close fitting. You might find it interesting from a strength standpoint. A two component systems (powder and liquid). can be used with heating during the assembly to speed up cure time. Open time is not unusually long at room temp. It is not designed to be gap filling - just ulra high strength structural wood connections. Unlike Epoxy, it is not affected by heat or sunlight UV exposure. Available through industrial supply sources only in my experience.

Hans

We used to use resorcinol for laminating F17 structural beams in the timber mill, really good adhesive, but leaves a very distinct brown line. Bugger to clean up once dried too.

 

[jeffinsgf]

[member=7266]jeffinsgf[/member]  - If your looking at other high strength adhesive options, RESORCINOL can provide extremely strong connections PROVIDED the joint is close fitting. You might find it interesting from a strength standpoint. A two component systems (powder and liquid). can be used with heating during the assembly to speed up cure time. Open time is not unusually long at room temp. It is not designed to be gap filling - just ulra high strength structural wood connections. Unlike Epoxy, it is not affected by heat or sunlight UV exposure. Available through industrial supply sources only in my experience.

Hans

We used to use resorcinol for laminating F17 structural beams in the timber mill, really good adhesive, but leaves a very distinct brown line. Bugger to clean up once dried too.

And quite possibly the nastiest smell I've ever experienced. I went through that mess exactly one time. Never again.

 

[Packard]

Here is a fairly comprehensive article on resorcinol.  It does not read like a product appropriate for type of work I do.  But read and make your own decision.
https://www.christinedemerchant.com/adhesive-glue-resorcinol.html

 

[ChuckM]

"less-than-perfect Domino joint fits"

What does this mean or any examples?

 

[Packard]

I would note that I used polyurethane glue once.  It was a difficult piece to clamp, so I used a bungee cord for that purpose.  An error.

The glue expanded and partially opened the joint. 

If you are going to use polyurethane glue, make sure the joint is securely clamped.