Using a Screen Breather with a Vacuum Veneer Press

Placing a screen between the press and the piece helps create uniform pressure and prevents veneer bubbles. October 14, 2008

Question
Has anyone had success (or failure) using fiberglass window screen material as a breather in a vacuum press?

Forum Responses
(Veneer Forum)
From contributor C:
I have used fiberglass window screen material in my bag press for several years. The screen is duct taped (at the ends only) to a loading panel (1/2" plywood). The screen slightly overhangs the sides of the plywood. I use a piece of polyethylene plastic sheeting on top of the screen (also taped at the ends but not the sides). I lay up my work on top of the polyethylene, then slide the loaded panel into the bag like a tray. Inside the bag, the loading panel sits on top of a conventional bleeder panel (scored melamine). Because the screen overhangs the plywood, the vacuum easily feeds from the bleeder panel to the screen under the plastic. When the glue has cured, I slide the loader out of the bag and peel the veneered parts from the plastic. I have used the same piece of screen for a couple of years, and usually get dozens of loadings from each change of plastic. The screen works well on curved parts also.

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From contributor D:
I use vacuum for veneering and am wondering what the purpose is of the screen you are using.

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From contributor C:
Without the screen, I used to occasionally get small air bubbles under certain veneers, places where the glue didn't take. Because the grooves in the bleeder board have some space between them, the vacuum doesn't reliably reach every square inch of a panel. Without a screen, the substrate presses the veneer tightly against the bleeder board, and effectively seals the area between the bleeder grooves, sometimes leaving air pockets. With the screen, the vacuum reaches all parts of the panel and sucks any air through the veneer. So, no bubbles.