Replies

1. 
   ted | Oct 28, 2008 03:09am | #1

   1) Old wisdom says wha you do unto one side do to the other.

   2) Have only done smaller veneer work with the new alphatic resin type adhesives. For me the jury is still out on this type of glue for large surfaces.

   3) To be safe overnite.

   4) I've applied finish to stuff the same day it came out of the press.

   5) I once did a 12' long table out of maple veneer that had a plywood core. I haven't seen or heard of any problems with it. (That was 11 yeas ago). I can't see how baltic Birch would be any different.

2. 
   sapwood | Oct 28, 2008 03:39am | #2

   Baltic birch makes a very good substrate. I have never bothered to cross orient my veneer from the face grain of the substrate. I think under your circumstances the paper backed veneer will be OK. In lieu of using that, I'd probably opt for an inexpensive and thinner than 1/16 veneer. But, I've done exactly as you are proposing without any mishap.

   I prefer Unibond 800 for most of the veneer work I do, especially on tabletops. There's less chance of any long term creep with the hard setting glue. It is also waterproof.

   I leave pva type glue in the press for an hour. In that time it will "set" and not come loose. You must leave it overnight (12 hours or so) to cure. It should be fully exposed to the air, both sides. You can leave it in the bag for a week and it will still only set. PVA needs to dry out and it won't do that in a plastic bag. Unibond sets and cures according to the instructions. You can vary its time by adjusting the catalyst and temperature. It has to be at 65º F to cure at all. The size of the panel is irrelevant to cure time.

   24 hours to cure the glue, then finish. That's just like any glue-up in my shop.

   There's lots of good info on veneer working at: http://www.vacupress.com/forum/forum-view.asp?forumid=3&catlock=1

3. 
   brad805 | Oct 28, 2008 04:52am | #3

   I would definetly invest in some Unibond for that table top.  The kick time of PVA will be a problem for those panel sizes.  Unibond is more rigid and will give you a lot more time to make final adjustments should you need to do so.  You would need to leave it in the vac press quite a bit longer, but I have almost ruined a large panel recently when attempting to get away with PVA on a 38"x78" panel.

   I recently asked a veneer expert about using paperback as backer with a wood face veneer, and he suggested against.  He didnt elaborate why, but he was a production fellow with years experience so I ordered some other.  Poplar, mahogany or any other straight grained veneer makes a great backer material and it is not expensive.

   Baltic Birch is a great substrate for a table top.  You will undoubtedly need to screw something on, and MDF would not work very good for that.  I know many on the woodweb use BB for tables.

   I think a week will be fine and by all means join the vacupress forum.  Not a lot of traffic there, but some very helpful very experienced veneer guys there.

   Brad

1. 
   JohnHarden | Oct 28, 2008 06:44am | #4

   Thanks for the replies.  I think I'll try a  few test pieces with my veneers and the Tightbond cold press veneer glue.

   Question.  Since it's a PVA glue, do I spread glue on both the veneer and substrate, or the substrate only?

1. 
   user-83153 | Oct 28, 2008 09:03am | #5

   John,

   You should definitely do a couple of trial runs before tackling that large panel to refine your technique.

   You are going to have the veneer pieces taped together and cut to the proper size before you apply glue to anything right? If so, you should be able to work with the shorter open time of the PVA glue. One thing I have found very helpful is to make the panel a couple of inches too big and cut it to the proper size after you have it veneered, just in case the veneer shifts a little in the press (it almost always does).

   Only apply the glue to the substrate. If you apply it to the veneer itself it will curl up like a potato chip and kick your butt when you try to get it in place on the panel.

   I haven't worked with veneer of that thickness, but I would be leery of using a different type and thickness as balance veneer. Especially on a panel that big that will have little or no mechanical means of holding it flat. You could try to locate a lesser species of solid wood veneer in the same thickness. I know it would make me sweat less if I were doing it.

        Rob

2. 
   brad805 | Oct 28, 2008 07:51pm | #9

   Substrate only.  If you apply to the veneer, by the time you have it on it will become very difficult to work with.  The PVA will become very tacky quickly after you finish rolling it onto the substrate and if you try to adjust veneer and it is very straight grain it will tear when you try to shift it if the piece is large enough.  I learned this the hardway.  I was applying a backer veneer for a crotch veneer (with PVA) and I tried to adjust it shortly after setting it down.  The stock started to tear and I then frantically re-taped the joints to salvage the piece.  Unibond is easy to work with, not that expensive and gives you between a 1/2 hour to an hour to get it all done and in the bag.  By all means, give it a whirl with what you have, but keep in mind time is the enemy and the bigger the piece the more organized you must be. 

   It was suggested to me once that it is ok to put the veneer tape down.  That does save the tape removal, but I would not recommend that.  What can happen (again, learned the hardway) is if any of your tape is not perfectly applied or say you have a spot where you put an extra bit of tape on, you can get an imperfect bond.  It will show up when you start finishing as a bubble and then you get to carefully cut the bubble, push some glue under and clamp it up.  Not any fun, I threw the piece out.

   Good luck

   Brad

4. 
   Jfrostjr | Oct 28, 2008 04:11pm | #6

   I have a note of concern about the "two halves and individual leaves".

   As another post explains, the veneer will undoubtedly shift. How will you be sure of a grain match between the various components?

   I don't have the answer - only the question. I await word from those who have faced this issue.

   Frosty

   "I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922

1. 
   JohnHarden | Oct 28, 2008 05:33pm | #7

   I've been thinking about that and on the adjoining halves of the table, I plan to tape the veneer down to the substrate with only 1/4"-1/2" of overhang.  That way, when I clean up the mating halves, the grain will match.  I'll do the same thing with the leaves.  I figure lots of blue tape to hold everything in place should avoid surprises.  The edge banding on the face of the plywood will be 1/4" thick or so, giving me some flexibility to trim into it if need be. 

   I'm getting worried about using the paper backed veneer on the back side of the table halves.  I may just bite the bullet and use the thicker veneer for this, then maybe use the paper veneer on the back side of the leaves.  They are only 12-14" wide and 42" long, so I'm hoping they'll hold flat easier.

   My worry is, if it goes badly, I'll not have enough veneer left over for another try "the right way".  On the other hand, by doing both sides with the good veneer on the first go, I'll surely not have enough for another try.  In that case, I'd just order two identical  4X10' sheets.

   Thanks for the responses.

   Regards,

   John

    

   Edited 10/28/2008 12:30 pm ET by JohnHarden

1. 
   brad805 | Oct 28, 2008 08:03pm | #10

   Are you planning to join the leaves with Blue tape?  That is not usually recommended.  Two basic problems.  The vac press will press the tape so tight to the veneer that it will beome difficult to remove and secondly, you might end up with some residue that will cause a problem with the finish.  I would buy some of the proper veneer tape, its cheap and easy to use.  

   1/4" overhang will be a bit of problem.  I always make the substrate bigger than the veneer assembly and final size after.  Overhangs will roll over and can tear at the edges.  I would size the substrate on the basis of your leaves in rough form.  Sometimes the cutoffs can be used in other projects.

   You might want to pick up a copy of Darryl Kiels Veneering DVDs.  You can find it at vacupress or Veneer Systems.  Veneer Systems is a great place to deal with and the owner (John Van Brussel) is extremely knowledgable.

   Brad

5. 
   tom77 | Oct 28, 2008 05:35pm | #8

   Good morning, John,

   I have had experience with large panels and with Unibond and cold press glues. I don't have any direct experience with thick veneers backed with thin veneers. Here are my thoughts on your questions.
   1. I would do a test panel about 2' by 2' to see if the two thicknesses cause a problem. There is enough risk to warrant a test.
   2. I have used a cold press glue from Joe Woodworker that has high solids content to reduce bleed through. It works well. You must apply it to the core only, or you will be wrestling a wet pringle.
   3. With PVA glues like the Titebond product, you should leave it in the press about an hour and then remove it to complete the curing process. Do not leave it in overnight, as you may get "black spotting". This is a mold, I believe, and is a fatal flaw.

   The Unibond glue is designed for veneering and is a urea formaldehyde resin. It is very temperature sensitive. At 65 degrees, it requires 12 hours to set. At 95 degrees F, it requires only about 2 hours to set. You should have a sample of unused glue in the same area as the vac press, so you can check it periodically to see if the glue is set. Most people use an electric blanket over the press to heat it up when using this glue. I built an enclosure of styrofoam and put a space heater inside that raised the temp over 95 degrees.
   4. You should let it cure for at least 12 hours before removing the veneer tape. Then let it dry completely before sanding and finishing. You should be able to apply finish within two days easily. It will take you that long to apply the solid edging.
   5. Your plywood should work well, since it is old and stable. Recent panels that I have used were very unstable. Definitely not suitable for this project. The only other drawback with plywood is the potential for the grain to telegraph through to the surface. You only see this after you have applied and rubbed out the finish. I think you will be in good shape with the thick veneer that you plan to use.

   Good luck and tell us about your results,
   Tom.