Replies

1. 
   migraine | Mar 16, 2004 04:54am | #1

   One of the problems that you are probably having is that the veneer is shrinking as you heat it.  I had this problem years ago when I tried using some sheets of thermal glue to bond red oak to a substraight.

2. 
   jackiechan | Mar 16, 2004 07:17am | #2

   Trad',

   To achieve a tight fitting veneer joint - joint the two edges and glue them together.  I'll explain - lay out the sheets of veneer side by side the way you want to see them on the finished piece.  Close one half over the other (i.e. a book) so that they are face to face.  Line up the edges to be jointed as best as possible, and then sandwich that edge between two long strips of (straight) plywood, MDF, (or other) so that no more than 1/16" is exposed.  Using a sharp block plane or router with a flush trim bit, bring the 1/16" down to perfectly jointed edges.  Remove the veneers from the clamps, and lay them back out side by side (open the book) face up.  Carefully line up the freshly jointed edges, and using blue painter's tape, run a strip the entire length of the seam.  Now apply a series of additional full length strips overlapping the first to the left and to the right.  For good measure, lay a series of small strips perpendicular to the long ones. 

   Gently fold one half back over the other so that they are face to face again.  Take a toothpick (or similar) and apply a thin bead of (fresh) PVA glue to the exposed edges.  Work quickly, you don't want the glue to dry before you've reached the other end.  I'd recommend using a slow set PVA.  The glue and taped seam will keep the integrity of the joint even after the substrate to veneer glue has dried.

   For this next part, I usually prepare a long strip of 1/4" plywood to four inches wide, and a few inches longer that the seam, covering it with a thin layer of clear packing tape to keep the glue from sticking.

   (Assuming you've done the above plywood option) flip the veneer book open, face up, with the bottom of the seam resting on the plywood strip.  Lay a long board on the top of the seam (on top of the tape) and either clamp it or weight it down.  Let the whole sheet dry overnight. 

   When dry, flip the whole sheet face down, but do not remove the tape.  Remove any glue squeeze out from the bottom, and then veneer your project as you planned.  Once the veneer has set to the substrate, remove the blue tape, and then sand and scrape - carefully so that you don't go through the veneer! 

   Instead of PVA gluing the veneer sheet down, you may want to switch to a Neoprene based contact cement - you get instant results, without adding undue moisture into the equation.

   If you have any questions, please feel free to ask!

   Dan Kornfeld, Owner/President - Odyssey Wood Design, Inc.

   
   

   ---

   Edited 3/16/2004 12:20 am ET by Jackie Chan

1. 
   tradclimbinf | Mar 16, 2004 03:01pm | #3

   Very interesting ideas.  Never considered glueing the joint together.

   Now, is there any way to reversed what I've done, or do I need to find some new veneer and start over?

2. 
   SgianDubh | Mar 17, 2004 01:59am | #8

   Dan, the two big questions with the methods you suggest are the use of blue painters tape and impact glue for the adhesion.

   Painters tape is quite thick, as is masking tape. In a heated bag press the adhesive in the tape softens and migrates into the grain of the veneer so that subsequent removal of the tape tends to rip the grain of the veneer out. Secondly, in either a heated bag press or hydraulic press the pressure is great enough and the tape thick enough that the tape will crush the grain of the veneer so that subsequent removal of the tape leaves indents which are very hard to disguise. Thirdly, neither blue painters tape, nor masking tape are really ideal with traditional hammer veneering using hide glue-- the hammer gets snagged up on the tape which which then rips off, and traditional thin paper veneer tape with a water based adhesive is generally preferable.

   Impact glue under single sheets of veneer I generally find a bit suspect. The glue line is very thick and it also suffers rather from creep. Coats of sprayed nitrocellulose based polish tend to cause the glue bond to weaken often causing bubbles in the veneer-- they use the same solvent, although other polishes cause less problems. Stiffer veneers, such as two ply and paper backed veneers are less subject to bubbling when adhered with impact glue, but the fault can still manifest itself. 

   But I agree that efforts to carefully line up the join as you suggested prior to veneering are excellent. Slainte.

   RJFurniture

1. 
   jackiechan | Mar 17, 2004 06:41am | #11

   Richard,

   I agree completely with your assessment of the pitfalls in using impact glue and the blue painter's tape.  My assumption was that Trad' was not utilizing either a heated bag press nor a hydraulic press in this situation.  You are correct, that the forces generated by each of these two pressed would literally emboss the blue painter's tape into the veneer, providing a permanent visual eyesore when the tape is removed.  I would discourage any use of a veneer hammer in this situation - the PVA glue being used lacks the grabbing effect of contact cements or animal glues.  Any use of a hammer would almost assuredly shift or distort the veneer regardless of the type of tape being used.  At the end of my reply to the original post, I recommended the use of a neoprene based contact cement of the veneer to the substrate, its easy to apply with minimal set up and decisively out performs the PVA approach.

   Slainte Mhath.

   Dan Kornfeld, Owner/President - Odyssey Wood Design, Inc.

   Edited 3/16/2004 11:43 pm ET by Jackie Chan

1. 
   SgianDubh | Mar 19, 2004 12:40am | #12

   Dan, you're correct that hammer veneering and veneer presses, heated or not, probably wouldn't be a factor here. I should have made it clear that I was commenting on the use of painters and masking tape for edge matching in those circumstances. I know they don't work well-- I tried it two or three times after thinking it would be a good idea.

   I also tried clear thin tape-- generically known as Sellotape in the UK, which did eliminate or reduce the imprinting problems, but it didn't resolve the adhesive tearing the grain out problem. Nowadays I stay with the brown paper veneer tape and its water based adhesive for pretty much all veneering jobs, unless there's a veneer seam stitcher handy.

   I haven't tried neoprene contact cement under veneer, but I've seen enough problems with using regular flammable contact cement under single sheets of veneer that the idea made me wary. Slainte.RJFurniture

3. 
   richk1 | Mar 16, 2004 04:38pm | #4

   I've used the dry pva glue method occasionally in the past with good results.  Initially, I had the same problem with the joints.  I overcame the problem by making sure there was alot of compression in the joint.  I did this by ironing down the first piece and then put a 1/8" diameter rod under the 2nd sheet parallel with the joint about 1" away.  I then use the iron to bond all of the 2nd sheet up to about 2" from the joint.  I then make sure the end of the veneer is butted against the first piece, remove the rod then bond the last 2" working toward the joint.  I have yet to have a gap appear after using this technique.

   In the future, also consider learning to use hot hide glue.  I use the same rod technique to create compression but the bond is stronger and has no creep.  It's also reversable if you make a mistake.

   Rich Knab
   People of mediocre ability sometimes achieve outstanding success because they don't know when to quit.

1. 
   creekwood | Mar 16, 2004 10:50pm | #5

   Have you ever considered using the hammer veneering method, with hide glue? Tage Frid explained it in Fine Woodworking On... Veneering and Marquetry. It takes some practice, but the results are worth it. Also, I wouldn't use contact cement on raw veneer, it never dries completely rigid, and has not been around long enough to see how it lasts on today's work when it becomes antique.

   Just a thought.

   I

4. 
   RMillard | Mar 16, 2004 11:13pm | #6

   I agree completely with everything creekwood said. Hammer veneering is great. I have veneered dozens of pieces with this method, some of them quite complex, and I've had only one failure. I tried to make a four point match in burl maple for a William and Mary lowboy top, that resulted in a less than satisfactory outcome. I believe I'd now be able to accomplish that top by hammer veneering, since I've developed more of an understanding of what went wrong with it. The learning curve is fairly short. If you'd like a description of the method, I'll try to write a reply. I've never tried the PVA and iron method, but I don't think much of it

   Rob Millard

5. 
   Clay | Mar 17, 2004 12:54am | #7

   It has been my experience that the PVA-iron method works well for small areas where the veneer can be overlapped at the edges ... excellent for edge taping for example.  I have not had good results with it on larger pieces and suggest that hammer veneering or press or vacuum veneering will be more likely ways to get the results you want.  When I make joints I use clamped and jointed veneers and then tape their edges with veneer tape on the glue side (real veneer tapes are made of VERY THIN paper which does not telegraph through the finished layup).  I have never had any problems with such joints developing gaps.  I like to use a press system (I made my own using solid core doors (salvaged) and slightly curved 2x4 cauls).

6. 
   scadaboy | Mar 17, 2004 02:16am | #9

   I too have had this happen on a book-matched night stand top. To salvage it, I carefully laid a straight edge on both sides and sliced with a very sharp utility knife to true up the gap (glue and wood). Carefully chiseled out the glue in the gap, down to the substrate, then chose a nice contrasting strip of veneer, carefully trimmed and glued it in, with fresh glue and compression so as to not create more shrinkage with heat. It also helps to pre-iron the veneers to dry them out and pre-shrink them before laying the glue on it. Tedious, but it saved the beautiful makore veneer top.

7. 
   Andrew | Mar 17, 2004 03:15am | #10

   what I do is joint the veneers and then lay them out on a flat surface and use short strips of masking tape placed perpendicularly over the joint to pull things together. I space these strips of tape about 12" apart, and then use real veneer tape in between the masking tape, running paralell over the joint. then once it's dry i remove the masking tape and glue the veneers to the substrate.

   hope this helps

   Andrew

8. 
   Tao | Mar 19, 2004 04:02am | #13

   Everybody seems to be overlooking one of the easiest traditional methods of getting a tight veneer joint. Glue both pieces down with a little overlap in the center, then use a straightedge and a VERY sharp knife (new utility knife blade at least) to cut through both layers at once, forming a nicely matched joint.  Then remove the waste and glue or iron down the veneer along the joint.  One of the reasons i like hide glue for this operation is that it seems to fill hairline seams a little bit and make them even less obtrusive.  Also takes stain well.

   If you are feeling particularly froggy, you can even angle your knife a little bit to make the overlap even tighter.

   I like hammer veneering with hot glue and vacuum pressing best of all the methods I've seen, for a small shop.  Contact cement is a definite no, and you don't have to wait long to find out.  I have seen too many problems on even recent work to ever trust it for anything but laminates.  I trouble shoot for a couple of large custom furniture manufacturers, and I fight this battle a lot with their production guys.

   Michael R.