Curing Time for Glued Door Joints

If you plane or sand door panels too soon after gluing, you might experience various defects. September 15, 2011

When we are gluing up solid panels for doors (using yellow glue, I can't be more specific than this, we get various different brands depending what our supplier has) we sometimes unclamp and start working the panels after 30 minutes. We prefer to give them more time than this, but sometimes the schedule dictates we "rush it". My question is this - is 30 minutes sufficient cure time on the glue or are we setting ourselves up for problems in the future?

Forum Responses
(Adhesive Forum)
From contributor G:
I'd say it depends on the temp and what type of machining your doing. Personally I'd give it at least an hour, maybe more if youíre running a big panel cutter.

From contributor E:
The problem you're going to run into is sunken joints at your glue lines. The wood swells from the added moisture of the glue and when you plane it too soon the wood will re-dry and you'll have a depressed area at the glue line. It's best to let it dry at 24 hours to avoid that. 30 minutes is enough for clamp time, but planing should be longer.

From the original questioner:
Here's some more info then. Temperature/humidity - we're in Calgary, so it's very hot and dry except when it's cold and wet, which it can be from one hour to the next. We plane our panels to 2mm thicker than finished size, then take them the rest of the way through our wide belt sander. Definitely more time consuming, but we find it to be faster than remaking a panel that the planer decided to eat on the last pass. Would the heat generated by the widebelt cause the glue to cure faster? I've been doing this for about 12 years but Iíve always want to improve my knowledge. I am currently setting up our standards manual, which to date has existed only in my head. Before I put it on paper, I want to make sure that there isn't a brain tumor in there!

From Gene Wengert, forum technical advisor:
There are two problems: first is that you can permanently weaken the joint if you machine it heavily before the adhesive is fully cured. As a general rule, it takes 24 hours. Second, the moisture from the adhesive causes localized swelling right at the joint. This swelling may take three days at warm temperatures to dissipate. So, if final sanding is done too soon, the panel will get sunken joints, as mentioned. This imperfection will be most obvious with glossy finishes. Some "yellow glues" are actually white glues with a yellow color added. This means that they will not have much strength after 30 minutes. There is no overall difference today between white and yellow glues, based on color. Some are good and some are not that good.

From contributor H:
Dorus Express glue works well. Iíve been using it for about two years, no problems at all. Ten minute clamp time if the shop is above 70 degrees, then run it through the planer if you need to.