Replies

1. 
   user-3395150 | Apr 04, 2023 04:44pm | #1

   My guess is that you're getting some air bubbles that aren't getting sucked out. There's a product called vacuum breather mesh that can prevent this issue.

2. 
   JoeU | Apr 04, 2023 04:58pm | #2

   Thanks for commenting. I neglected to mention that I did use the mesh on top of the top surface, although it did not cover the entire surface. I had used it before in the same way in several other projects.

   Has anyone else had this happen? I need to know how to prevent it, and also (very important now) how to fix it when it happens.

3. 
   user-210490 | Apr 04, 2023 06:19pm | #3

   I only use mesh over the inlet to the pump hose and have not needed more of it for good pressing. As long as you are using a platten both on top and bottom, have adequate glue coverage on both the substrate and veneer there should not be a problem. Make sure the bottom platten has grooves cut into it to allow air to evacuate. Titebond original is fine I use it all the time. Is it possible that there might have been a contaminant on the bubble area? I don't know if you are stacking the individual pieces but this can sometimes cause poor adhesion. Better to lay them out so each one is getting equal pressure. I don't know the system that you are using, I use something similar to a vaccupress. As far as fixing the bubble, take an x-acto knife and run a slit in the middle of the bubble, get some glue underneath and place a caul and clamp on top and press. You could also try using an iron and a piece of cloth to see if the glue will soften enough to be pressed back down.

4. 
   _mj_ | Apr 04, 2023 08:39pm | #4

   My best experience with the roarocket kit is with the mesh overlapping the entire part. I put the show face on the bottom flat to the bag.

5. 
   BillieRuben | Apr 05, 2023 04:21am | #5

   Honestly, modern adhesives make veneering SO MUCH HARDER.

   In many modern woodworking tutorials veneering is done with a PVA-type glue (e.g. Titebond) this isn't a great option for veneering in general because it requires you to clamp the whole surface evenly and firmly until the glue is dry (which is no small feat, as you have found!). PVA also resists surface finishes (varnish, oil, etc), which is especially important when doing marquetry which has a lot of seams. But can also be important in regular veneering as it can bleed through the wood.

   HOWEVER there is a marvelous glue that is perfect for veneering and has been used for centuries. It's the glue that every veneered piece in a museum is using: [animal glue](https://en.wikipedia.org/wiki/Animal_glue) (the real stuff, sold as granules, not in a bottle).

   While not vegan, it's renewable and readily available at fine art stores (rabbit skin glue) or leatherworking suppliers (hide glue). It *doesn't* require clamping when used in a process called [hammer veneering](https://en.wikipedia.org/wiki/Veneer_hammer), which relies first on water tension to hold the pieces together, then as the glue dries it tightens up and pulls the veneer *extremely* firmly (strong enough to [chip glass](https://youtu.be/G2HQP0jtldQ)) onto the substrate material. There's a good tutorial [here](https://youtu.be/o8Ubb659iXc) demonstrating how simple hammer veneering is.

   While it may seem like it's extra effort to warm a glue, the savings in time/energy/frustration far far outweigh the perceived inconvenience. Not only is there no need for clamping, the glue burns clean and safe with a laser, and you can apply any finish you wish over it, oil, water, epoxy, it won't show! Plus it's reversible and forgiving; if you make a mistake or decide you don't like something, wet it, heat it and remove it. It responds to humidity changes, swelling and shrinking with the wood, and thus won't crack with time. It can be used as a grain-filler on textured woods, and you have immense control over the tack and thickness of the glue (by varying the ratio of water to granules) and the gel time (by adjusting the temperature).

   If you have a 3D printer, you can use the bed to melt the glue (at 60C) and keep it warm (at 50C) without needing a double boiler, this completely eliminates the risk of 'cooking' it (denaturing it due to high temperature). Some people also use baby bottle warmers.

   The powdered glue keeps indefinitely and glue you have made up with water can be repeatedly frozen and melted for future use.

   Seriously. I wish I started using this glue a decade ago and I'm kinda a crazy person about it now. 😅

6. 
   JoeU | Apr 05, 2023 11:22am | #6

   Thank you to all people who replied. Something in user210a490's comment caught me: I did not have a platten on the top of the upper veneer. I think that might be the clue, as the veneered boards had the wrinkle only on the top sides I think. (I didn't notice as I was taking the boards out; only as I was stacking them on the table.) The boards were not stacked in the bag, by the way, but I had as many as 4 of them in the bag at once.

   I'm going to try the Exacto knife fix, thanks.

   BillieRuben, your advice to use hide glue and hammer veneering is convincing, and I am going to try it as soon as I get the proper stuff. Right now I am not going to experiment in the middle of the project, as you can imagine. Thank you very much for the extensive explanation.

1. 
   BillieRuben | Apr 07, 2023 02:24am | #9

   I can definitely agree/understand that strategy! Good luck with the repair. Fwiw I reckon ironing the bubble down (with a bit of fabric on top to protect the wood) is worth a try! Then if that doesn't work, injecting some more pva under the bubble squeezing it flat, and then clamping the bubble is worth trying.

   Maybe steaming it first to help it flatten down?

7. 
   DRBWWing | Apr 05, 2023 02:35pm | #7

   If the glue is dry you can reactivate PVA type glue with a hot iron and clamp a caul on for several hours. If the glue is wet, or if there isn't enough glue, you can make a slit with a razor blade and either squeeze out the glue or inject glue. Again, clamps and cauls or wait for the glue to dry and hot iron.

   I like hide glue, too but its not practical for that many pieces. And you already have a press. That said, hammer veneering is a really neat way to veneer.

8. 
   vespid | Apr 05, 2023 05:58pm | #8

   Way to long in the press, one hour is all you need and should do. There is moisture that needs to " get out" and a vacuum will not allow that to happen. Though you are using 1\16" veneer.

   Also you might be using too much glue.

1. 
   BillieRuben | Apr 07, 2023 02:26am | #10

   If you keep sucking with the vacuum it will pull the moisture out. It's something that painting restorers do when flattening brittle paintings. They humidify it and put in on a warm bed and apply a vacuum made from a piece of plastic, taped to the table.

1. 
   JoeU | Apr 07, 2023 05:01pm | #11

   I agree about the vacuum eventually "pulling" the moisture out. It doesn't really pull; the wood has a vapor pressure of 150 microns or so, and it will outgas even into the low vacuum I am able to get.

   Anyway, thank you to you and the others for all the helpful advice.