This week at a class on veneering projects the instructor said Unibond 800 (a catalytic glue from Vacuum Pressing Systems) was reformulated a couple years ago. He said he never uses it any more, because of a problem with dark blotches. He showed me a panel with dozens of dark blotches. They appeared more than 6 months after it was completed. (Everybody’s worst nightmare)

He’s no amateur. The panel was gorgeous until the blotches appeared. He sent it to a chemist at Franklin (makers of a competitor, Titebond) who confirmed the problem is the glue. But it’s not the bleed-through that everybody gets (rapidly) with open grain veneers.

Is this problem widely seen? Is X-press glue also a problem? I really don’t want to switch to a glue that water or heat will affect.