Over the last couple of years I’ve used more and more of my own re-sawn veneer on furniture projects and I like the way you can get a nice consistent or book matched appearance. I have come to appreciate this as a way of using some of the more exotic woods more efficiently. Most of the time, I use a vacuum bag to apply sheets of edge-glued veneer onto the substrate.
I have a job coming up that I would like to use the vacuum-bag process on, but the piece is far larger than my 9 foot bag – how has everyone solved this problem? Would it be possible to cobble together a one-shot vacuum bag with visquine and duct tape? Could the bag be taped to the substrate itself? Any help would be appreciated.
(Furniture Making Forum)
From contributor B:
I came upon a situation like yours where I had a piece to glue which was longer then my 8 foot bag. I used a pretty flat bench topped with a 4x10 sheet of 3/4" Mdf. I then tapped the sheet for a vacuum connection. I ripped up strips to elevate the work piece/substrate (positioned over the vacuum tap, this acts like the grooves cut into your board in bag system).
Then I laid up the substrate and veneer, and caulked on the top. I then had some 6mil polysheeting laid over the whole thing and duct-taped to the MDF table. I pulled a vacuum and there it was – it wasn’t perfect, but it held 12-13 inches and ran my pump constantly. For the one shot deal it worked great. With a little tweaking and a better membrane or seal, I don’t see why it wouldn’t work perfectly. My veneer was very flat to start with and only a 26x112" size.
Whenever I need a one-off bag, I use cloth core carpet tape which is sticky on both sides. I keep rope caulk handy for stuffing a little pinch into any wrinkles, and around where the hose passes through the film.
On really large projects, I find it easier to do the glue-up right on top of the bottom half of the bag, then just peel the tape and stick the top and bottom halves together. I have not had any problem holding 25" Hg. on projects over 20' long. I usually use epoxy for my adhesive for this kind of work because of the longer open time and lubricity for bending.
Some of the poly films that I have used had to be cleaned with acetone to get the tape to stick, then it seemed barely adequate, but by the end of the cycle, it could not be removed. Also, use cautions or dull any sharp corners.
Comment from contributor T:
I use clear shower curtains for a vacuum bag. They come in 60 x 72 inch sheets. I trim off the brass rings and stick the suction cups on the outside of the bag. I seal the edges with swimming pool liner repair cement. The only drawback is the bag tends to seal very quick around the valve stem before the entire bag is under vacuum. 30 x 24 areas are no problem, though. Since the bag is so cheap, I have several made and have 4 or 5 bags under vacuum at one time. Just pinch off the hose with a "C" clamp and remove the hose from the pump. My bags hold vacuum overnight. Larger bag can be assembled from several curtains. They are only 10 mil vinyl but seem to last a few years for me.