Applying glue to both sides of a joint?

[transatlantic]

Just wondering what people here do.

Do you apply glue to both sides of your joints or only one? .. or it depends.

Although you always hear people saying that you should, and although I've taken that advice, .. it's always struck me as being overkill? Surely if your joints are tight, only applying glue to one side (and then shifting the boards back and forth to further spread it) should be enough as it's going to spread when you tighten your clamps?

The only reason where it seems to make sense is when using those glues that you apply to both sides and then let sit of 5 minutes before making contact between the two.

The reason I ask is because life could be made much easier when using the fast drying glues. (I know that there are slow setting ones out there)

Has anybody done any experiments with this? using one of each method and testing the strength of the joint?

 

[custard]

Festool did some experiments and found applying glue to both the tenon and to the mortice (using a Domino) resulted in a 30% stronger joint. Of course there are situations where reducing squeeze out is well worth accepting a slightly weaker joint, or other situations where the short open time and "grabbiness" of PVA means it's only practical to coat one component in order to get it all cramped up in time.

So the best course of action is probably to coat both sides, unless there's a compelling reason to do otherwise.

 

[biskit]

I've always coated both sides to ensure full coverage, not leave it to chance. (hammer)

 

[Jacob]

Both sides, all over, no gaps, every time.
Test it yourself - glue on one side, clamp it tight and pull apart (quickly!) and see how far the glue has spread. Usually much less than you expect.
No point in going to all that trouble to make something and then skimp on the glue and leave weak points.

 

[Phil Pascoe]

This crops up periodically. Why then do most manufacturers advise you to coat one side only? (don't shoot me, I'm only the messenger )

 

[MIGNAL]

Both sides. Much better chance of avoiding a starved joint. I've also found that glue sizing with Hide glue can result in a stronger joint. Probably not the case with other glue types though.

 

[transatlantic]

Both sides. Much better chance of avoiding a starved joint

But if there is a starved joint, the wood between the two faces won't make contact anyway. Is filling that gap with glue going to help?

 

[Jacob]

Both sides. Much better chance of avoiding a starved joint

But if there is a starved joint, the wood between the two faces won't make contact anyway. Is filling that gap with glue going to help?

It's the way the glue spreads (i.e. fails to spread) even under pressure and perfect surfaces with no gaps. But yes if there are gaps then more glue will certainly help.

 

[Phill joiner]

PU only one side as it expands and reacts with moisture in the timber. Water based glues always both, as it needs to soak into the grain. That's my reasoning anyway.

 

[Benchwayze]

FWIW I also 'size' end grain with glue, and let the first couple of coats soak in, before I complete the joint. The only failure I ever had was Cascamite on cedar-wood. I think that might have had something to do with the natural preservatives in cedar, as the glue wasn't 'out of date'!

HTH :wink:

 

[Stormer1940]

So what is the best way to get glue down a 1/2" mortise with a 100mm door stile without getting in a complete mess?

 

[Phill joiner]

So what is the best way to get glue down a 1/2" mortise with a 100mm door stile without getting in a complete mess?

You should insert the tenon half way and only glue the shoulders. This allows the stile to swell or shrink and not split. The wedges also are glued to the sides off the tenon.

 

[Jacob]

So what is the best way to get glue down a 1/2" mortise with a 100mm door stile without getting in a complete mess?

Squirty glue bottle and palette knife.

 

[Stormer1940]

Sorry don't want to sound stupid but how do you mean only insert tenons halfway?

 

[Phill joiner]

Sorry don't want to sound stupid but how do you mean only insert tenons halfway?

Insert halfway and then brush the glue on the shoulders. So assemble the door dry but only push the stiles onto the tenons half way and then brush glue on the exposed joint. Simples.

 

[Stormer1940]

Sorry don't want to sound stupid but how do you mean only insert tenons halfway?

Insert halfway and then brush the glue on the shoulders. So assemble the door dry but only push the stiles onto the tenons half way and then brush glue on the exposed joint. Simples.

Thanks. Thats kind of what I thought you meant. Think I was getting confused when people have been talking about both sides I assumed as in both sides of the tenon and the mortise.

 

[Benchwayze]

So what is the best way to get glue down a 1/2" mortise with a 100mm door stile without getting in a complete mess?

Squirty glue bottle and palette knife.

Or save the kids' flat lollipop sticks. I usually have a few in an old jar. Good for spreaders on edges, and use as gauges too!

 

[Phil Pascoe]

I used to get them from a local c & c in packs of 100 or 500 (can't remember) - if you know someone with a ticket. Handy for small jobs - filler, epoxy, all sorts.

 

[Benchwayze]

eBay seems to have a few sellers. There are one or two arty/crafty shops selling them. Most seem to be a bit expensive, but just this minute, in my desk drawer I found about fifty in an elastic band! Whaddayah know! :lol:

 

[devonwoody]

Costa used to do nice wooden spatulas at service stations and there coffee price covers