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I’ve made a fair number of workbenches using Southern yellow pine (sometimes called longleaf pine) and it’s always been a challenge to get tight joints that stay closed after years of abuse and seasonal contraction and expansion.
As I dove deeper into designing this Roubo-style workbench, I realized that gluing up this workbench would be more difficult than any other Southern yellow pine project I’d attempted. Of course, I reached that conclusion while unloading the $230 worth of material from my sadly overloaded Toyota pickup. The resinous surfaces and the weight of the 2 x 12s reminded me of all the difficulties I’d had in the past.
So I decided to see if I could make it easier.
The next morning my first phone call was to Dale Zimmerman at Franklin International, which makes Titebond. I’ve worked with a lot of glue people in the last decade, but Zimmerman has always been they guy who would give it to me straight, even if it didn’t benefit Franklin. For certain applications, he’s even steered me to some products (epoxy and plastic resin glue, for example) that Franklin doesn’t even make.
Here’s the Southern pine gospel according to Dale: He doesn’t consider the wood to be particularly difficult to glue under normal circumstances, but it is denser and more resinous than many of the easy-to-glue pines, such as white pine. Both the density of the wood and the resin work to prevent moisture penetration. And because PVA glues rely on moisture to wick into the wood, this can sometimes be a problem.
After explaining the workbench’s top to Zimmerman (it’s made of 20-something lengths of 1-1/4″ x 4 x 8′ pieces) he had some recommendations. The first is to wipe down any resinous areas with some acetone right before gluing up. The acetone would help wipe away the resin temporarily to allow the glue to penetrate. I’d used this trick before on teak, and cocobolo, but I had used lacquer thinner.
Zimmer said lacquer thinner and mineral spirits (another common chemical used this way) were bad ideas. The reason is they evaporate too slowly and will also prevent the glue from penetrating into the wood.
“In this case the cure would be worse than the disease,” Zimmerman said.
Acetone is flammable, so take care with it when using it.
The other suggestion was to keep the top laminations in clamps for far longer than recommended. Most yellow glues recommend you keep the parts clamped for 30 minutes to an hour. But with a heavy-duty glue-up like this one, Zimmerman recommended four hours, especially if any of the pieces were bowed. No matter how carefully you machine your pine, you’re going to have some pieces that warp or bow on you. Gluing these is like gluing up a bent lamination, said. And so it’s perfectly reasonable to keep the project clamped up longer.
For the last two days I’ve been gluing up the top. I have one more joint to go and only one sliver of a gap in 19 of my 8′-long joint lines. Thanks Dale.
– Christopher Schwarz
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