A veneering disaster (Long)

Did you put baking powder in your glue?

Denis Ch�nard, Orl�ans, Ont.


>Sorry, couldn't resist :)

Too bad about your experience, but it kind of convinces me that I should put hammer veneering lower on my "to learn" list...

Now what's the best hammer for the job, framing or Warrington? :D

DC

Re: Did you put baking powder in your glue?

Paul Kierstead


>Well, my previous experiences have been quite positive, albiet much smaller areas and with better behaved veneers. I would still encourage anyone to try it out.

Of course I use a shop-made hammer :)

I'm no help but...

Scott Burr in Ben Lomond CA


>Could it be that oak is so porus that it's causing the problem?

Did you pour some Coke in the hide glue? (just kidding)

I for one would like to hear about attempt no. 4 when the time comes.

Thanks for sharing.

Re: A veneering disaster (Long)

thomd coralseacat@yahoo.au


>I don't get the problem. I assume you have completed some small test sections. The big pieces are basically the same idea, but you lay it down and go over it with an iron, anywhere your glue goes hard. Then hit it with the hammer working out. Once it's hammerd down in a wet state to a thin glue line it flashes off instantly and you can't get it back up again without heating again or solventing. You have to work small sections at a time. Don't try to get the whole surface down in one go. Do a piece the size of a postcard at a time, then move on.

At that point the only reason it will bubble or bulge would be if your glue was not correct and it wouldn't tack, you can check this by seeing if it makes a standard rubbed joint or glues your figers together. Or because you don't have enough glue, which can result from working it down tight then cycling it over and over. Or maybe contamination. If your veneer is so wavy like lots of bendy birdeyes that you can't get it down in the first place, that's a whole other thing, but if it goes down it should stay down.

I only had one period when I was doing a lot of this, and the first big piece I did was a 4 way match table top, along with a friend who was qualy cherry. It just wasn't that hard. You are using a veneering hammer? We had the Dujinsky video, and a few magazine articles.

I don't think using "real" bandsawn veneers will make it easier. Hammer veneering pretty much depends on the veneer being thin enough that the pressure from the hammer is decisive, and the hammer itself can cool/heat sink through the veneer, and you can refresh the heat with an iron as required. None of that sounds like a given with thicker stock.

I stopped doing this stuff because I don't like veneered furniture myself. but it was fun.

I can't remember why but some folks top coat a little with glue to hold the heat and allow the hammer to slide and protect the veneer. I just washes off.

Re: A veneering disaster (Long)

Dean J in MN


>Sorry if I missed in somewhere in the thread -- what gram weight of hide glue are you using? I've had better luck with the pearl glue (192 g. I think?) for veneering than my regular 251 g. glue I use elsewhere.

I apply the glue to both sides as well, but still work in small sections. Reheat as needed.

-D

192 g ...

Paul Kierstead


>Again, though, I recognize the value of working in small section, but perhaps I need to clarify:

The problem is not just one of glue adhesion. If you cut one of the air bubbles, there is significant overlap when you lay it back down. The veneer has had quite a lot of size expansion. As I noted in #3, the edges of ajoining secions push so hard against each other, the came up like two tetonic plates and made a mountain. This was only in certain area. The pieces were jointed and fit nicely beforehand.

However, I would like a blow-by-blow account of how to work in section, especially if the veneer is quite delicate (which this certainly was).

I previous veneering jobs, I occasionally didn't hammer perfectly and the glue would not be adhere everywhere. A simple iron and re-hammer fixed it. In this case, you would not even remotely be able to iron it down; you would have to cut the bubble, lay it down, saw through the overlapped bits and then do it.

16 pound sledge ;-)

Dan Donaldson

Mountains

Barryvabeach


>Paul, I am not going to be of much help with a solution but maybe I can help in defining the problem. I recently hammer veneered what was called cigar box mahogany ( whatever that means). The problem I saw was not air bubbles but expansion. If I did a wide piece, it would seem to stick fine but a 5 -15 minutes later, the two edges were stuck well and the middle bowed up a lot - at least 3 - 4 inches. When I tried to get around it by using smaller pieces, I recalled hearing, from the harpsichord maker at Williamsburg - that when they do cross banding they do a small piece, skip a space, do a small peice and skip a space, then come back in and fill in the skipped spaces ( you have to reheat the egdes of the first pieces to cut the joint) I tried that and I ended up with exactly what you described - while the filler pieces went down fine, a few minutes later I saw the edges where the pieces met were forcing up like a mountain. I decided, though I may be wrong, that the problem was the veneer was expanding from moisture and that force was overwhelming the glue and forcing it away from the substrate ( you can check this by veneering a series of small pieces ( 5 inches wide or so) with some space in between to see if they stay flat after they cool - if so it is not air bubbles or a problem with the glue. The way I "fixed" it was with an iron and a spray bottle. At this point all the "mountains " were at the seams - spray it lightly with water then as you iron it on either side of the mountain it dries out and contracts and using the veneer hammer I could push the veneer around so that it reduced the mountain till it flattened. If you hit it with the iron too much, it dried too much and the seam came apart so I would hit it more with the spray and then use the hammer to move the pieces closer. So it was a lot of back and forth with the iron and the water. This worked fine in some spaces - not so great in others because what you are shooting for is enough water ( or dry heat from the iron) so that the wood fibers are pushing against the seam so much that when they dry the seam won't open up, but not so tight they they bubble 10 or 15 minutes later and of course you can't tell that when you are doing it. It is my guess that the reason you did not have as big a problem with the shop veneer was that is has less expansion - contraction with moisture ( more quatersawn) though that is just a guess. Keep at it though, because since then I have veneered some other pieces using a tiger stipe mahoganoy and didn't have that problem at all. Barry

Re: Mountains

Paul Kierstead


>No, that is a lot of help actually. Yes, it would definitely seem it is due to a lot of veneer expansion. I have another suggestion on wetting/flattening the veneer, which sounds like it might help too; it could help even out the moisture in the veneer. Try #4 could be hot hide glue yet again....

Re: Mountains

thomd coralseacat@yahoo.au


>You need to start in some place and work out, just like putting film on a window, but even so, the nice veneer is never flat and you just have to force it down with the edge of the hammer and let the glue take over. this stuff will chip glass so wood is not going to pop out unless the glue is shot.

I did a stain glass project once where I bought the edge of some glass where it had pooled up, and was inconsistant thickness. I was not able to cut a single piece of that glass without it breaking, like graham crackers. I just had to tot it up to experience. Sometimes the materials are impossible. I had a similar problem with some mahogany on a boat shear, every single one of the pieces broke by the end. Just crap wood. So maybe you have a materials problem, but if this kind of stuff is happenign all the time, then you need to return to the basics. The glue, the materials, the process, not overworking it, etc...

Try #4

Paul Kierstead


>Well, contrary to my plans, try #4 was with hide glue.

Additional Steps:

Pre-wet, and clamp for a bit to flatten. This, I believe, was by far the biggest help. It seemed to significantly help with the un-even swelling at application time.

Applying it in sections(23" x 2"). This veneer still didn't like to bend across the grain, so I was wary of not doing a full strip at a time.

The results were much better. There were still a few areas of raised up veneer; one very bad one that was almost certainly me not working out to the edge of where the glue was, and the rest almost entirely on the 'far' side, where the veneer had been getting kind dry by the time I reached it.

The key to fixing these much better was the use of water to soften the wood, as Barry described. I switched to a heat gun as it is more precise then an iron (and mine goes pretty low).

Not perfect, and repair took too long, but acceptable results and I am convinced it will come out better next time. This is the first time I ran into these sorts of problems; OTOH, it is the biggest I have attempted as well as first time for Oak (which definitely is less ruly then the others I have done)

Many thanks to Thom and Barry (And Colin!) for the help. I got it under control again.

Still curious about that vacumm thing, though. I need an excuse to keep it. Hmm. Maybe a small bent lamination.....

Re: Try #4 - Success

Barryvabeach


>Paul, I would label that a success. I had not thought of a heat gun and that is a great idea - one thing I did with the iron was to use a rag under it - when I wanted the veneer to expand, I used a damp rag and that forced in moisture and swelled it. I'm sorry I forget to mention prewetting the veneer and letting it dry - I also did that but don't remember whether it helped much. Keep at the hammer work , when I saw the guys at Colonial Williamsburg, they could really fly in laying the venner - much faster than putting it in a vacuum bag and waiting for the glue to dry. Barry