Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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When there are more than a few pieces of marquetry, a starburst, or other more complicated sheet of veneer, I generally make a pair of two plies, one for each side of the substrate. The "show" side of the back side of the substrate may be a simple veneer with grain all in the same direction, but I've seen too many suggestions to treat both sides of the substrate the same.
Typically I'll make a dry run, the mix the urea formaldehyde glue and get the pair of two plies in the vacuum bag by 10:30 or so, with the room thermostat raised to 70 the night before and a heating blanket on the vacuum bag and grooved platen. The extra mixed glue in a baggie, under the heating blanket, usually is very rubbery by 4 or 5 at the latest. I don't like to trust the electricity, pump, et cetera so I'll leave everything untouched, with the pump and blanket on, till morning.
The two plies have not dried out at all, because they stayed wrapped in 4 mill plastic overnight.
Then I trim the two pair of two plies and glue to the substrate the following morning.
So there's still a lot of moisture in the two plies when they get glued to the substrate.
I'm hesitant to leave the two plies open to the air that night, to dry, because they might warp and the glue become rigid overnight. But I don't like having all that moisture in the two plies when they are glued the next morning.
Thought about turning off the pump, removing from the vacuum bag, and placing between pieces of MDF overnight with top weight so they'll stay flat and perhaps lose some moisture to the MDF before morning.
What practice has others used in this situation, and how did things turn out?
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