The 10,000th test of PL gluesBy Phil Keck #39 "S.S. Pubert" (5ar)
The guilty parties.
We'll be gluing lauan to oak.
Everything all glued--two pieces of each glue type glued to the edge of the oak, and one of each glue type glued to the face of the oak.
Two test pieces were glued with each glue, and the glues were allowed to cure for about 50 hours. This should be plenty long for all of the glues except for PL Concrete--it needs at least a week. However, I've used this glue a lot already, and have a high degree of confidence in it, so I wanted to see how it would hold up if it wasn't allowed to fully cure.
In this picture, you can see that I pulled each type of glue apart with some pliers, and as expected, the glues holding the plies together failed before the PL glues did. Left to Right: PL Plus, 400, Premium, and Concrete
Next I left the remaining glue joints to soak underwater for 7 full days to see if a good soaking would weaken them.
Pulling Apart After The Soak
No pliers needed to pull this apart. The glue released from the lauan, and pulled almost none of the wood apart. (Ignore the joint on the right side that has some wood still on it, that was from another test.)
This required pliers to get apart, but not as much force as the PL Premium. The wood failed in a couple of spots, but the glue mostly just pulled off of the wood. I only let this joint cure for 2 days though, and the bottle says it should be allowed to cure for a week. I'm sure more cure time would increase the strength.
No pliers required to get this joint apart. It took very little force to get it apart. The glue readily released from the wood, and pulled none of the wood apart.
This one required pliers to get it apart. The wood failed over about half the joint, and the glue failed over the rest of the joint.
Final results (in ascending order of strength):
-PL Plus was basically worthless after a week in the water;
-PL 400 was slightly better than the PL Plus (but considerably weaker than before it soaked);
-PL concrete was slightly better still (but I didn't let this stuff cure for long enough to get accurate results);
-PL premium was weakened slightly by the water, but still remained strong enough to pull the wood apart.