How much Working time with carpenter's glue?

Answer 1

As you can imagine, the answer is 'it depends'. Some major factors that the time it takes for carpenter's glue to dry include: Temperature, Humidity, square feet covered (distance from air), and to some degree, the material you are working with. There are probably some slight differences with different manufacture, but we've used several brands and our working rules of thumb seem to stand for all of them.

In general, the warmer the temperature, the faster it is going to dry.

In general, the higher the humidity, the slower it is going to dry.

In general, the more porous the material, the faster it is going to dry. Both because the glue will 'leak' into the pours and become thinner and because the material will let air at the glue from more directions.

In general, the greater the square feet covered, the slower it is going to dry, but more than square feet, it is a question of how far the glue in the middle is from the outside and how long it is going to take for the air to get to the glue. This last one can mean the difference between hours and days or weeks. Imagine you are gluing 2 fairly nonporous (air can't get through) materials together, the air has to come in through the glue on the outside until it gets to the inside. The glue could take months to dry.

Now, you probably care about 'normal' circumstances. I can tell you that we assume that the carpenters glue is going to take several hours to dry. For cabinetry - using 1/2 or 3/4" material, we like to leave it overnight (12-16 hours) and have had no problems with it not being dry and solid. For this - our shop runs at about 13C/55 F for as much as the year as we can (we like the cooler temperature for working) and we are fairly dry. So if you are more humid but 20C/68F, I expect you will get similar results.

Here is an exact test that we did: Using 3/4" MDF, we glued with a thin but full cover layer of carpenter's glue (Weldbond II) on the END of 3/4" MDF. Then we glued and clamped it to the flat surface of another piece of MDF. So we glued an end joint of 3/4 to a flat side of MDF. We glued and clamped a whole bunch of pieces to test. After 20 minutes, the first piece we tried to break off came off easily and the glue was obviously wet in the middle. After 2 hours we tested and it required full force to break it off, and it broke a fraction of an inch below the glue, meaning the MDF was now the 'weak joint'. We tried several other pieces and each time, it broke the MDF, not the glue, in each case it was the flat surface of the MDF, not the end joint, that came away with the glue. Now, while there may be conclusions of how to get a better glue joint, the result of the test for this question is; After 2 hours, at 13C/55F, with low humidity, the glue dried to stronger than the wood through 3/8ths inch (half of 3/4 since it would dry from each side. We still try to leave it overnight to be safe (in case higher humidity) but realistically, for most of our work, carpenter's glue is dry after a few hours.

If you need to know if it is going to dry sooner, I suggest you take several boards and glue them together then at, say, 10 minute intervals: force them apart and see how far they are dry. If they break on the glue - they aren't dry, if it is the wood that breaks/rips/tears, then they are 'dry enough' meaning that the glue is now stronger than the wood, so you don't care usually if it is fully dry, just that it is no longer the weak point. This test will tell you how long it takes to glue for your temperature, humidity, materials and thickness.

Madmanpierre's information is excellent. As an experienced cabinetmaker, the answer to this question often broke down to a simple question: what is the clamping time?

a. for PVA glue (Elmer's glue/polyvinyl acetate/white wood glue): 24 hours

b. for carpenter's glue (aliphatic resin): 30 minutes

Answer 2

About ten minutes working time - For a really good joint I always clamp it for 4-6 hours .