Thread: Veneering with vacuum press bags?

Mate Im not sure about NZ, But try www.rivergumtimbers.com.au in Queensland im sure they will post it to you
regards Chowcini

John, when you do find a suitable supplier, make sure the minimum size you get is 2.4x1.2 as you can roll up the length not needed when vacuuming. If you have table tops in mind some time down the track, a 2700 length is the go.

Thanks for the tips. I read a bit further on Joewoodworker and found he has guides for making your own bags too.

I am wondering about technique now, since veneer I want to use is only 0.6mm thick, how careful would I have to be about the edges of the sheet I am working on? I mean, presumably you have to leave some overhang around the outside to be trimmed off with a router after the glue has dried, but if you leave too much hanging over would the vacuum bag possibly tear or split the grain of the veneer around the glued edges? just trying to get my head around the method.

Also, how well would veneer glue to the "end grain" of MDF? I am considering CNCing or routing some curved pieces to sandwhich together to obtain a curved front and back panel for the floorstanding speakers I want to make and so would have to glue veneer to the edges of the pieces. Perhaps I would have to prime those edges in some way prior to glueing to minimise how much glue soaked into the mdf?

Hi Johnnz,

I did quite a bit of vacuum bag veneering for furniture including curved pieces. I'm going to toss out a few tips and please follow up with questions. You want some overhang of veneer but you need to have a caul or "cover plate" that distributes the actual pressure. We used 5 mm melamine on flat pieces and bendy ply with a covering of packing tape or wax paper for curved convex shapes. We tried for a 5-10mm overlap to account for slippage. Curves are a bit tricky because the bag tends to compress from the end closest to the vacuum. Often, we made our form several cm longer in both directions so we could trim and square the pieces. It's a bit of a race to compensate for the bag pressure and any weird air bubbles you get. If you you don't have a thicker cover plate (caul), the vacuum bag will crush your edges, splinter grain, and make a real mess from the glue being forced up over the top of your veneer. We glued edges using 3M Spray 90 or yellow glue. Contact adhesive works but may slip from the heat of sanding. Veneer the edges and trim with a router~ a flat file work great too, then veneer your faces so they over lap the edges. Also, the top edges of your forms need to be rounded. Vacuum presses create huge pressure per square cm and you will tear your bag if you don't round over all you edges and corners. Depending on your design, you may need a backing veneer.

I would strongly suggest you do some dry practice runs as well as some mock ups with cheap veneer so you don't ruin your good stuff on the learning curve. There are also variables with type of glue and the thickness you apply it. The vacuum bag will force glue through your veneer to the face if applied too thick and it will mess with your finish. Too little glue, and your veneer will not adhere and bubble. It's a bit of an art form but approach it scientifically and you should do fine.