This is a useful tip but should be used with some wise discretion.

When you do a glue up between boards sometimes the boards will shift as you clamp under pressure.

Let's say you are making some table legs. Each leg is made of two 2x4s. You evenly spread glue on each mating surface and just before you bring the two surfaces together you sprinkle just a wee bit of table salt here and there in the glue. Just a little bit.

Then you clamp. The pieces won't slip. The glue crystals act as a non-slip anchor.

While drying the salt gets absorbed by the glue.

Just be careful you don't use too much Salt.

Experiment first.

I have always wondered how much reduction in bond strength is created by this method. Have there been any definitive studies?

There are opinions about it here and there but I don't recall seeing any definitive studies. A few woodworking magazines have made comments about it. For sure it can be poor if you use too much. I would think an overdone excess would cause adhesion failure. There are just as many opinions favoring it.

However we are literally talking just a few strategically place grains. Under this control I have never had an issue.

Cool tip! I'm trying this one next slippery glue up.

@John Morris Be sure you sprinkle only a few grains evenly distributed across your glued surface. Don't clump them. Try to use only a few grains here and there.

Cheers! You'll love how steadfast it is... your boards won't move. Then clamp.

A couple decades back I suggested this trick to a student who was gluing up a stack of boards that were already cut to size and had to stay aligned when clamped up.

First thing the student did was give the first layer a hearty sprinkle (way too much) of salt. ☹️

Then he asked if pepper would have also worked since it would be easier to see in the glue.

Kind glad I'm now retired from teaching.

4D

Gee... you only need like one or two grains. Good grief!!

In the old days my grandpa used to use very small brads, tap them in slightly on one of the mating parts, and cut the head off. He'd then applied the glue, mate the parts, and clamp.