Veneer question

[Frank D.]

Hi Everyone,
I'm doing some veneering for a humidor and I ran into trouble when I bookmatched two pieces for the top: the joint between the two pieces of veneer looked fine (it was tight) when I glued up and when I took off the clamps, but several hours later it opened up, so there's now a very small gap bewtween the two pieces of veneer.
This is the first time I'm working with commercial veneer (eucalyptus). I usually saw my own veneer, and glue two bookmatched pieces together by the edge before gluing them to the backing (in this case, birch ply). I didn't glue the two pieces together this time because they were wavy and a lot thinner than my own shop-made veneer, so it seemed like a difficult task. I just taped the two pieces tight before glue-up.
I'm going to redo the top, so here are my questions:
1. Should I try to glue the two edges together anyway, before gluing them to the backing?
2. Or should I just leave the tape on longer as the glue dries out?
Any help or suggestions welcome. Thanks in advance,
Frank

 

[Shady]

How thick, Frank? Normal commercial stuff over here is so thin that it wouldn't be practical to glue the edges: you would just stick down and tape.

If it were me, I'd check grain direction etc: did it open up uniformly from the surface to the underside, or more at top than bottom? If the latter, flipping the veneer might actually close the gap as it dried out...

 

[Scrit]

Hi Frank

What glue are you using and are you laying down the veneer at right angles to the grain on the groundwork (assuming that it's "real" wood or plywood in the first place)? I'd leave the tape on until the glue has dried then scrape/sand it off (with some water to soften it, perhaps).

Scrit

 

[Frank D.]

Hi guys,
Shady, the veneer is really thin, about .5 mm. The gap seems pretty even along the joint and depthwise. I checked the direction woth the substrate and it's cross-grain so it shouldn't be that. I used Titebond II. I think I should have just left the tape on longer. I had no idea that things could move so much after 24 hrs. Someone told me to try to heat it with an iron and close the gap so I'll give that a try before starting over.

 

[Colin C]

Frank
If you do use an iron, make sure its not to hot as it might make it worse.

 

[Frank D.]

I put a moist towel on the piece and went out for a jog. When I came back an hour later the joint had closed up, as tight as when I glued it up! I tried the iron just for the hell of it, but as soon as the wood started drying out the joint opened up again. I have a towel on it again, and I'll tape it up when the joint is tight, but something tells me it'll separate when it dries out...We'll see.
What I don't understand is how I can avoid this happening again. Seems to me that no matter how tight I have the joint at glue up, it'll separate on me when the piece dries (the veneer will shrink and move again).
Maybe I should use glue with no water in it (poly, or contact cement which I don't like)???
Or maybe I should just go back to my thick shop-made veneer...

 

[Colin C]

Hi Frank
I am not sure this will help but this is one of the reasons that I still use animal glue as you can take the tape off the next day with no problems.

I would say try to leave the tape on for longer and see how it goes, I have not used many glues for this or you could try Excormite ( I am sure I have not spelled that right but I hope know that I mean ) :roll:

 

[jasonB]

Did you apply glue to both surfaces, if you did this will have caused the veneer to swell, you should only apply it to the groundwork when useing titebond and thin veneer.

I apply one caot and let it soal in a bit then another one about 5mins later and not too much, a foam roller gives an even coating.

Leave the tape on for 24hrs then scrape it off, assuming you are using veneer tape and not something like masking or scellotape.

Jason

 

[Chris Knight]

Frank,
I always preglue the pieces if the edges are straight and it is perfectly possible with even thin veneer in my experience. I use 3M blue masking tape for this (other colours either stick too little or too much). Tape at right angles across the dry joint first whilest butting the pieces together - can help to have an asistant for this - then along the joint. Then fold the pieces so the joint opens and put a littlle PVA into the crack. Close up and leave under a weighted flat sheet od MFC or similar.

To avoid shrinking, yopu could try the pre-glued iron on method - see Mike Burtons book, especially the bit on preloading the joint - worsk perfectly every time.

If using conventional methods such as animal glue and making up the joint in-situ, use papertape for the the joint and make sure it is well wetted beforehand, so that as the tape dries it shrinks and helps pull the joint together. Leave the veneer to dry for as long as possible before removing the tape - I aleways leave it a week at least.

 

[Colin C]

If using conventional methods such as animal glue and making up the joint in-situ, use papertape for the the joint and make sure it is well wetted beforehand, so that as the tape dries it shrinks and helps pull the joint together. Leave the veneer to dry for as long as possible before removing the tape - I aleways leave it a week at least.

Hi Chris
I would agree with most of that but the only veneer I would leave as long a possible would flame mahogany ( not sure what Frank knows it as ) but I have still taken the tape off the next day with no problem, just have to make sure you dont use too much water when taking the tape off.

One of the big problems with veneer IMO is that people try to lay it before getting it flat ( Just wipe it with a wet cloth or with thicker veneer quickly running it under a tap and clamp it flat )
Or in wetting it and getting it too wet, with can end up with the same problem with gaps on the joints.
All that needs to be done is to get some moisture back in the veneer to make it more plyable and easier to cut

 

[Chris Knight]

Colin,

I certainly forgot to spell-check my post!

Just to clarify, I find that when using animal glue, it contains so much water that as it dries out the veneer has a tendency to shrink which the paper tape can overcome to a degree at the joints - depending on the area of the veneer involved. I don't do a lot of hammer veneering so my technique is quite likely at fault, probably getting too much glue on everything and possibly stretching the veneer to boot as I lay it down. Two reasons I particularly like the pre-glued method is that the surfaces are no longer wet and the glue on the veneer holds it flat and also gives it a lot of strength so it's not so easily damaged whilst handling it.

 

[Colin C]

Chris

Did you see the post I did on hand veneering , all of people might do if not shown is like you said is stretch the veneer, which the tape will not hold if it is stretched to much.

I am not sure how you do your joints when using animal glue but I lay the veneer with the twp pieces over lapping and then cut both with a sharp knife and a straight edge, to get a tight joint.

I might give the way you do it a go some time but for some of my bigger jobs I think animal glue would a quicker for me at the moment

Some veneers will need wetting and pressing first, like burrs that have dried out to make sure it does not break up when it is being used .
I have also read a way to tread burrs so that it can be backed and will stay flexable but for the life of me I have not found it yet ( most look for it again :-k )

 

[Frank D.]

Thanks so much for your help everyone!
I did a little research and found detailed instructions for the dry PVA iron-on method. I've heard of this method before, and the cabinetmaker who sold me my veneer also uses it, so I'll give it a try if the joint is opened up again when I take off the clamps (I suspect it will be). I'll start the whole shebang over again, because so much glue squeezed up into and onto the veneer that I'm afraid I won't get uniform results when I finish the piece if I use two different methods. I do have enough veneer left, I got 150 sq. feet for 25 pence per sq. foot, so not much pain there other than a little time lost.
My biggest problem was that I transferred the methods I had learned from Krenov's books (using thicker shop-made veneer) onto the thin commercial stuff. They are different beasts entirely.
Thanks again for sharing your thoughts!