The 5 stickiest wood glue questions with expert answers

2 drops of white glue
When glue no longer flows out evenly, like the dab on the left, it won't bond properly.

How can I tell if my glue is still good?

A wood glue will bond strongly as long as its consistency remains fluid. If the glue becomes stringy or rubbery and cannot be restored to a normal viscosity by stirring or mild agitation, discard it.

Will freezing destroy my glue?
White and yellow wood glues contain water and will freeze at temperatures below 32° F, but when returned to room temperature, they'll be unaffected by the process. If the glue appears grainy and thicker after it's warmed, the creamy consistency usually can be restored by kneading the bottle. As long as the glue flows out smoothly (right) when applied, it will bond well.

How much clamp pressure is needed?

Wood glue develops its best strength in thin, consistent glue lines. A carefully machined, square glue-up should only require a thin bead of glue (near right) and enough clamping pressure to produce a small amount of squeeze-out, like that shown at far right.

2 photos together
An aftermarket glue bottle, like the one shown above (Glu-Bot, #62979, 800-279-4441, rockler.com) provides more control over glue flow.

How long should I leave clamps on?

For well-matched pieces glued under ideal conditions (the moisture content of the wood from 6 to 8 percent, temperature from 70° to 80° F, and humidity from 40 to 60 percent), leave the clamps on for at least an hour.

For assemblies that require extraordinary clamping pressure, such as bent laminations, leave the clamps on for 24 hours. This allows the glue to achieve nearly full strength.

Quick Tip! Mark the time you glued up each assembly with chalk (photo right) to know when it's safe to remove the clamps. You can then reuse those clamps in another glue-up.

Higher temperature, drier wood, and lower humidity speed drying time; while lower temperature, wetter wood, and higher humidity slow it.

Glue number on boards

Can I take a dry glued joint apart?

Joints made using white and yellow wood glues are most easily taken apart by applying heat. Use a heat gun (photo at right) on the joint line to soften the glue, and the joint will open with slow, steady pressure. Wood has good insulative properties, and it may take awhile, so be careful not to damage projects with the intense heat.

Using hair drying on board
White glues react to heat more readily than yellow, but a heat gun set to a low, 150° F heat still reduces the strength of the latter by half.

2 drops of white glue
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