I've noticed something unexpected while testing PVA glues for strength.
Glues tested: Titebond Original, Titebond III Ultimate.
Wood species: Beech and Pine (and other unknown hardwood species).
Transverse to transverse grain joinery. All mating surfaces sandpapered.
Control: Glue applied evenly to both surfaces with brush then clamped straight away for 24h.
Test 1: Glue applied evenly to one surface with brush, then left to dry 1 hour. Then glue applied evenly to both surfaces before being clamped 24h.
Test 2: Glue applied to one surface with brush, excess glue scraped off with sandpaper (leaving surface moist), left to dry 1 hour. Glue applied evenly to both surfaces then clamped 24h.
I had expected the control joint to be stronger than test 2, and test 2 to be stronger than test 1.
In reality, the joints would seem to be equally resistant to sheer stress and longitudinal traction. All joints had barely visible glue lines, the difference between test 1 and the others is in the range of microns suggesting most of the dried glue had been absorbed into the wood during clamping.
The results seem to be reproducible, meaning this could have implications for correcting errors in assembly, or repairs and maintenance of cured glue joints.
Do you think this is unusual, given what we know about how PVA glues work?