Vacuum Bag Platen Details

Fine points of vacuum bag platens. December 1, 2005

I made my first vacuum bag. It is about 4' x 5'. I made two 1/2" MDF platens 4' x 4' with a 2" scored grid on one side. Works great. Can I leave the lower platen in there for everything and just make an upper platen to match an item? For example, if I were doing a 2' x 2' panel, could I just make one 2' x 2' platen to go over the panel and set them both on the 4' x 4' lower platen? I realize that for larger pieces, I can place blocking around the piece.

Forum Responses
(Veneer Forum)
From contributor J:
The piece that goes over what you are pressing - top platen - should be a little bigger and does not require grooving.

From contributor P:
We use two platens in all of our bags:
1) a lower platen with grooves
2) another platen same size made of melamine. This is slid in and out of the bag and when out of the bag, rests on a pair of sawhorses at the same height as the lower platen. We press all flat panels with the veneer laying on the platen, and place the glued up blank on top of the veneer so that the blank acts as its own platen. This is done outside the bag and then the platen, veneer, and substrate is slid into the bag. The glue won't stick to the melamine, and it is easy to pop it off the melamine when you are done.

From contributor B:

I use a lower platen sized for the bag I'm using (grid up) and then I cut a separate lower and upper platen from 1/4" hardboard or 1/4" vinyl coated hardboard just slightly larger than the piece(s) I'm pressing. If your main platen (with the grooves) is used without this smaller platen on the bottom of the veneered piece, the grid lines will cause the substrate (especially if the backing veneer is thin - I often use plain phenolic sheet) to be transferred as shallow ridges in the backing veneer where it is sucked into the lower platen's grid lines. I also cover the smaller custom cut platens in some 4-mil plastic sheet for squeeze out.