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Darryl Keil
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Dear Francois,I almost always make my panels large and trim the panel to size later without overhanging the veneer. This solves a lot of your questions. In general I do not like veneer coming right to the edge of a panel, so overhanging the veneer is not necessary.As a rule I leave a panel glued with PVA glue in the bag for a minimum of one hour, two wont hurt. The bond takes place from glue penetration into the veneer and substrate, drawing the water away deeper into these materials. The cure takes place when you remove the panel allowing the water to evaporate.As far as different veneers in the same pressing, let the open grain veneer be the gauge for how much glue to apply, the closed grain one will get plenty of glue.With wrinkling of the veneer, this is usually about over gluing or waiting to long to get into the bag. I am assuming you are using a rigid cover sheet, like 1/4" masonite. If you are not that could be the problem.SincerelyDarryl Keil : I have been experimenting a bit lately and I have some questions:: When do you trim the veneer edges? If I wait for the glue to cure : completely, then the drips are quite hard, making it quite difficult : to cut the veneer edge, especially on crossbanding. Should I trim : shortly after taking the works out of the bag even if the glue is not : quite set yet or what?: On that matter, how long should I leave a piece glued with white PVA : glue in the bag. Since the bag is sealed, I don’t quite see how the : glue can cure completely.: Also, how much overhang should the veneer sheet have. I leave about ¼ : to ½ inch sometimes to keep the crossbanding edge from crumbling at : the corners when I do the layout cutting. The problem is that when the : overhang is a bit wide, it becomes difficult to trim when glue to thin : substrate (1/4").: I have also noticed some glue starvation at the very edge of the : veneer. It is not because it needed more glue as the glue is beading : off the edge. I was wondering if I should veneer on a substrate larger : than the veneer sheet and trim the substrate later. : How do you handle the gluing problem when mixing close and open grain : veneer on the same face? If I reduce the amount of glue to prevent : bleed through on the open pore veneer, won’t I get glue starvation on : the closed pore wood. : I did get some problem with getting more glue in one area than another : and getting some bumps. When I first pressed the sheet, all was even, : it is only after about 1 hour that it became noticeable in one major : area and a bit here and there on the cross-banding. I used a roller to : move the glue away. Was this caused by uneven glue spread or could it : be caused by some veneer buckling letting the glue accumulate in that : area. I thought that the even atmospheric pressure would keep the glue : spread evenly, even if it might not have : been spread that way.: I have done a test with fiberglass polyester resin to glue a sheet of : mahogany to a piece of luan plywood and did not get very good results. : Lots of bleed through but glue starvation at the edges. The bleed : through does not bother me on this piece as it was meant to go : outside. The edge gluing problem is trickier. It seems the plywood : edge sucks all the glue in. The major advantage I found is that you : can press a piece, wait 20 minutes and it is ready. I guess next time, : I will glue to a larger plywood then trim later.
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