Veneer problem

[Matt Allan]

Well I applied the back piece of veneer to some MDF last night, used the long cauls like suggested with a slight crown and clamped everything down real good.. I got a few long bumps in the veneer when I unclamped this morning.

Is that just from too much glue? and it not getting spread from enough pressure or just plain too much glue? So the veneer gets bumps? This side doesn't matter, it isn't seen but I would hate to have this happen on the other side which I wanted to glue up today with the different pieces of veneer.

Thanks

[Donnie Raines]

Matt,

My reaction was "to much glue". When you apply the caul and clamp it up, if there is no room for the fluid to disperse, it will try to escape outwards...thus your get the bubbles.

Did you use a roller to some what flatten the veneer prior to clamping?

[Matt Allan]

Couldn't find my J-Roller, looked for 20 minutes before the glue up so I figured I would risk it since its only the back.. I tried to roll it out by hand with a decent size dowel to at least give it a shot..

Guess I better find my roller before I do the front.

[Donnie Raines]

The roller really does aid in pushing out any air pockets that may be trapped in the glue, or from the veneer being postioned.

[Roger Barga]

The bumps may be glue, but IMHO the problem is not enough pressure or uneven pressure. Even if you applied excess glue, it should have squeezed out from the pressure of clamping (especially for such a small panel). One contributing factor may have been the order in which you clamped down your panel. When I glue up a panel using clamps (as opposed to a vac press) I tighten the clamps in the center first and work out towards the edges - this helps move the glue in the right direction. Another factor may have been that your caul was flexible and didn't apply enough pressure - I typically use a 1/2" caul on both top and bottom (around the veneer and mdf substrate) and then clamp the heck out of it (from the center out).

Hope this helps,
roger

[Don Abele]

Matt, I agree with what others have said. The likely culprit is too much glue and uneven clamping. A hand-held dowel does not exert the same force as a J-roller for evening out the glue under the veneer. Additionally, as Roger pointed out, starting with the cauls/clamps in the center and working out will help to further squeeze any excess glue/air out. With enough pressure (like a vac press), it doesn't really matter because it'll squeeze the be-jeebers out of it. For the top I'd find that J-roller and give the veneer a good going over (starting from the center and working outward at angles). Then use the cauls/clamps from the center and apply them as close together as possible for the number you have. Then go back the center and retighten in an outward pattern. Veneering without a press is possible, just not easy. Best of luck.

Be well,

Doc

[Thomas Prondzinski]

Matt
Did you spread the glue evenely before applying the veneer? If you didn't it may have caused the glue to pool up and not spread out causing the bubbles. I don't think you will be able to roll it out because most if not all the glue has set.



Tom

[Steve Jenkins]

When pressing veneer like this use an adhesive roller to spread an even coat on the substrate. The glue should not be so heavy you can't see the wood through it. Do not put glue on the veneer. After you lay the veneer on the panel, cover it with a piece of something that the glue won't stick to when it seeps through the veneer. I like to use freezer wrap with the shiny side to the veneer. Next I would use two layers of 3/4 mdf to distribute the pressure from your cauls. The cauls could be as simple as some 2x4s with a slight convex curve cut on one edge so when you clamp both ends the center contacts first then pulls down across the panel. Put the first one in the center and work both ways from there. On small panels I have skipped the cauls and used some deep throated clamps that reached to the center. Steve