Page 1 of 3 123 LastLast
Results 1 to 15 of 35

Thread: Laminating "Thick" Veneer - Do I Need to Vacuum Bag?

  1. #1
    Join Date
    Oct 2013
    Location
    SE Kansas City Metro, MO
    Posts
    661

    Laminating "Thick" Veneer - Do I Need to Vacuum Bag?

    I'm working on a project where I'm resawing veneers about 12" wide and planing to ~1/8" thick, with the intention of laminating the veneers on both sides of a 1/4 or 3/8" substrate to build up a 1/2 or 5/8" panel.

    Not sure whether I can effectively get this done using clamps only, or if I would get better/faster results with a vacuum bagging system. Already have the vacuum pump, so it's not a huge cash outlay to get set up with a bag - but if it's not necessary, I probably won't go to the trouble. I've done a little bit of research regarding the use of vacuum bags but really don't know much about it at this point.

    Appreciate any advice that might get me pointed in the right direction!

  2. #2
    I would ( and have ) used Weldwood plastic resin glue. Apply to both surfaces, put 'em together, cover with a plastic bag,cover that with a piece of plywood, put spring clamps around perimeter and a weight it the middle. That glue pulls down as it sets.

  3. #3
    Join Date
    Apr 2003
    Location
    Birmingham, AL
    Posts
    335
    Is a vacuum bag necessary, probably not. Would it help do the job, absolutely!!!

    About 10 years ago I built a Demilume table featured in Fine Woodworking. The author used 1/8" mahogony veneer and on a round apron. At the time I was teaching a class for the local Woodworking Guild and our class built 6 of these tables using his plan/article. We used a vacuum bag for the veneer and it worked perfectly. He used clamps. Some friends of mine were taking a stringing class later from this author and questioned him about the veneer method. He admitted to them that he would have used a bag but Fine Woodworking wanted him to use a more traditional method.

    If you plan on doing more veneer work or get into bent laminations then I would recommend you treat this as an opportunity to get a vacuum bag. Good luck either way.

  4. #4
    The "safe" approach is to get a bag - they really work well. But if you use lots of clamps, and cauls to pull the center down, it will work. I did it that way before I got a bag.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #5
    Join Date
    Aug 2013
    Location
    Princeton, NJ
    Posts
    7,235
    Blog Entries
    7
    I did a project with a lot of veneers of this size and larger and about that same thickness. I used a bag but I wouldn't say it can't be done without it (I don't know). I used cold press glue and when that ran out at the last minute I did the last few panels with Titebond III. Both worked fine, the cold press glue a little easier to deal with in the press. Titebond required more time in the press IIRC.

    I've used wood weld, or attempted to before, I can never get it right so I just stick with what works for me.
    Bumbling forward into the unknown.

  6. #6
    Join Date
    Dec 2008
    Location
    Northern Michigan
    Posts
    4,963
    I have done it both ways with equal success. I use epoxy usually, but that is just me, I like epoxy. I have made slightly curved steel cauls, wood cauls, and the bag. DSCF3084.jpg

    For example on this one with 1/8" makore veneer it was too hard to get perfect fits of the wedge shaped pieces using a bag. What I did was apply every other one using a bent steel caul, then did the remaining ones by tapping up into place. There was a center bolt to pull down the cauls in the center.
    Last edited by Larry Edgerton; 12-13-2017 at 12:23 PM.

  7. #7
    With an area that small you could use PVA glue. But the plastic resin is thin and,I think ,less messy.

  8. #8
    Join Date
    Nov 2012
    Location
    Southwestern CT
    Posts
    1,392
    If you already have the pump (as you indicate) vacuum bagging is a no-brainer. It is easy and the results consistent and excellent. If your finished product is flat, you can use a single-sided plastic film on a platen such as plywood or preferably plastic, or more convenient in practice is an appropriately sized bag. If the result needs to be flat you would likely use a platen in the bag. Vacuum significantly slows the cure time on aliphatic glues though I'm not certain why from a chemistry perspective. To my knowledge their strength derives from cross linking as a result of drying (not oxidizing). But my experience from practice is that that bagging slows the cure process.

    I have frequently laminated 1/16" and up to 1/8" with no difficulties. Typically I use epoxy which has more predictable cure time in a vacuum environment, and better gapfilling qualities.

    Good sources for supplies are Jamestown Distributors (boats) and Fibreglast.
    Last edited by Bill Adamsen; 12-13-2017 at 12:43 PM.
    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  9. #9
    Join Date
    Feb 2013
    Location
    Duvall, WA
    Posts
    706
    For an earlier bookcase project (view pics in my album: Bookcase - IKEA Valje copy ), I used contact cement and a j-roller to apply a 3/16" thin veneer of CVG Doug Fir to a substrate of 3/4" birch plywood. I decided on contact cement based on a number of posts I'd read on this board and on a couple of other well used woodworking related message boards. In this case the veneer is thick enough that there's no risk of bleed-through, though it's still thin enough that grain movement isn't a significant issue. The reason for the vacuum bag method is to ensure an even distribution of pressure across the entire surface of the lamination. Likewise, you can achieve something close to that even distribution using a cover sheet of some kind (plywood, for example). I'd read that a veneer roller is more effective than a j-roller because it applies the pressure force over a smaller area. That pressure is intended to ensure the veneer and substrate materials are making contact, and to force out any air bubbles that might be trapped between. In my case, I was more concerned about scratching or compressing the relatively soft Doug Fir, so the rubber of the J-roller and it's wider dimension seemed like a better alternative.
    Last edited by Mike Ontko; 12-13-2017 at 5:58 PM.

  10. #10
    Join Date
    Nov 2012
    Location
    Southwestern CT
    Posts
    1,392
    Larry's point is good ... not everything is a candidate for vacuum bagging. If using a true bag, the "wet" assembly needs to be able to be picked up and installed in the bag while wrapped with breather fabric. When done you will want confidence that nothing has shifted. Typically a one sided film (or mechanical cauls) is easier to apply if there is a fragile glueup.

    Mike actually touched on the first thing I thought of ... contact adhesive. It is very fast and if the specifications work, that's a real alternative.
    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  11. #11
    Join Date
    Oct 2013
    Location
    SE Kansas City Metro, MO
    Posts
    661
    Thanks for the replies. I believe I'll go ahead and order the few additional bits I need to set up a vacuum bagging system and see how it goes.

    I did some more research this morning and, given that I'll be using a thicker veneer (1/8"), it seems there's a good chance that contact cement wouldn't stand up to seasonal movement of the veneer; in fact, joewoodworker.com recommends using a PPR (pre-catalyzed powdered resin) glue for shop-sawn veneers specifically because of it's additional bonding strength. So I'm gonna give that a try as well.
    Last edited by Marty Tippin; 12-13-2017 at 7:55 PM.

  12. #12
    Join Date
    Dec 2006
    Location
    Las Cruces, NM
    Posts
    125
    Marty,
    Please let us know how it turns out. I am about to embark on a similar adventure with 1/8" veneer only without the vacuum system.

  13. #13
    Contact cement is made to last about 10 years ,and the reps will tell you that. Yes ,sometimes it can last longer.

  14. #14
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,599
    You will be happy you got a vacuum bag set up. Flat work, curved work, it can do it all.

    I'm glad you saw that comment by Joe W. with regards to PPR glue. I had a very bad experience with his Cold press glue with 1/16" thick shop sawn veneer. Total disaster actually; I'll never use that stuff again on shop sawn veneer.

    I like Weldwood Plastic resin glue (PRG) for shop sawn veneer. 1/16" for most interior work, 1/8" for interior door skins, and 3/16" for exterior door skins. If you read the literature for that product you want a lot of pressure to affect a good bond and minimum glue line at the recommended coverage. A few hand clamps around the edges of a large panel won't do it. Cauls might get you there, but the vacuum bag is a far better and easier approach, even though the absolute pressure is less than Weldwood recommends. For hand clamping epoxy is a far better approach because you don't need, nor really want, high pressure. Epoxy works great in the vacuum bag, too, and I would probably use it exclusively if the cost were not high compared to PRG.

    One last tip. If you have to make up edge seamed panels of shop sawn veneer, glue the edges before gluing them down to your substrate. That will prevent any unwanted opening of those seams. Learned that one the hard way. TB III works fine for that.

    John

  15. #15
    Clamps around the edge won't work without a weight in the middle. The plastic resin glue pulls down as it sets. That was shown to me many years ago. The cautious can add a couple more weights. Bags and pumps will soon be FREE as current owners dispose of them to buy new ones that will serve as clamps for gluing , making all their clothes fit in a pic nic basket, and curing "dysfunction". But not all at one time.
    Last edited by Mel Fulks; 12-13-2017 at 4:36 PM. Reason: make more better er

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •