A veneering disaster (Long)

[Paul Kierstead]

This started somewhere else, but seems to be a lot of highly experienced people here, so thought I might toss it in here too.

Recently I had one of those days in the shop where I was worse off (i.e. less completed) when it ended then when it started. I was trying to hammer veneer some oak veneer onto a substrate and hade some air bubbles. Here is a description of the disaster.

It is an interesting thing. I had never hammer veneered Oak before ( and will hesitate to do it again ). Interestingly enough, the air bubbles certainly weren't random; they mostly studiosly avoided the dark, rough areas of the oak and stuck to the lighter denser wood. You could actually see them follow the grain. It isn't entirely clear which bit expanded enough (either could cause the problem).

The Disaster.
-------------
I started with a carefully prepared piece of ply wood with 3/8" edging planed flush. I want the veneer to be over the edging, hence the order. We also have a quantity of 24" wide oak veneer, insanely thin, one piece (no joins).

Try #1. Heat glue. I warm the substrate some with an iron to give a little more working time. The iron is standing by. Apply glue to substrate, apply glue to veneer, flip veneer and apply glue to the other side of the veneer. Start hammering down. Now clearly it is a problem to get it all down well when doing such a large area, and I "create" a couple of problem areas my self. I get out a knife and fix those up with the iron. While I am doing that, new problem areas start to appear. And then more. As I fix them, more and more appear, often well away from where I am working. Frig. Iron is too hot as well, and now the shop smells awful. Double frig. Not what I said. Eventually, I stop in dispair an just look; there are far too many areas to fix. Get the iron, a water spritzer out and remove veneer. Bah.

Try #2. This time I thin the glue a little more for easier spreading and hoping for a little more working time. Follow same procedure, but careful to work methodically from the center out. Outside of a little lifting at the edges, I don't really create much problems directly. While just sorting an edge out a bit, wait I notice a new air bubble. Then more and more. Soon, there are quite a few, although less then try #1, it is way too many. Remove again. I am getting better at removing cleanly, if not applying ....

At this point, I only have enough veneer to do one side. Plus, I have a pretty good idea of the outcome. Hmm, I thinks, maybe some shop-made veneer, a little thicker and applied in narrower strips (only 8" wide boards) might be the order of the day. Here, we have the secondary disaster. First off, some farting with the fence previously had resulted in it not being perpendicular to the table. Hadn't noticed as normally I don't use the fence face to register. rubbish, some ruined. Adjust the fence. Had done a ton of pine sawing on the BS in previous days (house stuff), the blade is pitched up, the tires a bit pitched up, and the drift angle has changed as a result. A couple more screwed up before I figure that out and eyeball a new drift angle. Then, the lack of fence height finally bites me, and the resulting veneer is not coplaner, nor consistent in thickness. Sigh. Will, it is practically usable, so long as I can flatted afterwords. The morale here is don't resaw for veneer when really pineappled off and out of patience. It requires care and methodical work. Anwayay, I have enough shop veneer to do it, but it varies in thickness. I'll try it anyway, just to see the general outcome. Joint the edges of the veneer, ready to go again.

One issue here is the substrate has some irregular bits of hide glue one it. I just hope these will remelt nicely and evenly.

Try #3. I do it strip by strip. Again some edge curling, but not terribly for the other stuff. The uneven heights make it difficult, but I did the thinnest stuff, generally speaking, first, making it a little easier. A little edge curling as usual (I really need to conquer that...) but all in all, not awful. 5 min later, one of the really thin and wide ones (about 7 1/2" wide) develops a huge bubble, about 3/4" high. Sigh. I leave the shop and go get a beer and watch some Good Eats on the PVR. Return the next day. It is interesting. The narrowest one (and incidently the first one layed) has gone perfectly. It is also the best sawn one, a pretty nice even 1/16" or a tiny bit more. It is flat and even. The huge bubble remains. What has also developed is some severe distortion along the edges where they join. Clearly one piece or the other (or both) has expanded a lot in certain areas, and the edge has pushed up, mountain-formation style. Must have been nice veneer quakes in there when that happened.

Try #4 will be with the 24" wide veneer + hand pumped vacuum veneer bag + modern glue. I will return to how to do this hammer veneer style another day, but for now (in the interest of project completion) will stick to hammer veneering smaller items, or at least narrower.

Two very notable problems when doing this:
1) the large area all at once really runs the glue-gelling before your done problem. This makes it *really* hard to hammer the excess glue out from underneath. This was clearly one general problem

2) Oak really reacts to the heat and moisture of the glue, much more so then my previous stuff (mostly cherry and maple). Even pretty thick stuff reacted a fair bit.

Just thought I would share and invite and comments or thoughts.

 

[Colin C]

Hi Paul
I have some things to ask you.

Did you wet and press the veneer before you started laying it as this does make for an easier job.

Which way did you hammer the veneer, I mean did you go with the grain or across it ( going across is a big no no as it can lead to the veneer spliting )

As you have guessed trying to do that all at the same time was a big mistake. When I am doing a big area, I will do it in sections so that the glue does not go off before it can be hammered.

You can try how I do mine


Here
I hope it helps

 

[Paul Kierstead]

Did you wet and press the veneer before you started laying it as this does make for an easier job.

No. It might have been a good idea. However, the veneer had some curl, but no bumps or "wave" etc that you would see in something with "interesting" grain.

Which way did you hammer the veneer, I mean did you go with the grain or across it ( going across is a big no no as it can lead to the veneer spliting )

With the grain. There were no splitting problems. I should clarify that the air bubbles were *very* significant; this is not just a lack of sticking down, but significant expansion of the veneer. If you cut the bubble and lay it back down, in some cases there is quite significant overlap of the two sides (indicating how much the veneer expanded).

As you have guessed trying to do that all at the same time was a big mistake. When I am doing a big area, I will do it in sections so that the glue does not go off before it can be hammered.

I will have to try to develop that technique some. It might be challenging to bend up the veneer for the next section in order to slide some glue under there. Now that I would love to see a video of; it would probably be invaluable.

You can try how I do mine

That is pretty much dead on how I do it, except I do not thin out the top coat generally (only one glue pot!)

 

[Colin C]

Hi Paul
Wetting and pressing the veneer, helps alot with the problem you had with the bubbles.
From what I have see, if the veneer is to dry. Then it will take on the water from the glue unevenly, which is why wetting and clamping is a very good idea.

This also helps you bend the veneer to get the glue under it and you can use the water in the pot to thin the glue for the top coat, this what I do

As you will have seen in my tread, I also have a bucket with some hot water too and you can use this.

What I do is to have all the things I need to hand before I start with the hot water in the bucket last.

I hope this helps and good luck for next time
Ps I was very lucky to be tought by some very good makers

 

[Paul Kierstead]

Ah, Colin, I don't know whether to thank you or curse you for your advice. I now have a hankering to go home, mix up some more glue, press out some veneer (I presume you wet, place between kraft paper and press between some boards?) and have another go. Ah, I know I'll thank you because it is sound advice.

One Q: Lets say you had an area both to wide and long to do in one go, what pattern would you use to tackle it?

Many many thanks.

 

[engineer one]

your last q is definately the question of how long is a piece of
string.

what is the pattern on the veneer.

most might think making the most of the cathedral would be
the way to go, but where is the panel going to go,how visible will
it be??

it is actually no different than when choosing real wood, the pattern
depends upon how you see the face.

paul :wink:

 

[Paul Kierstead]

your last q is definately the question of how long is a piece of
string.

what is the pattern on the veneer.

Ah, sorry, I was not clear; I am referring to what pattern one would use to apply the veneer, which is assumed to be already either a single piece or joined into a single piece. So there is much bending, etc involved.

 

[engineer one]

oops :?

paul :wink:

actually the perceived wisdom is always to cover the shapes
first, then do the flat surfaces last.

 

[Colin C]

Ah, Colin, I don't know whether to thank you or curse you for your advice.

I have never had that before :^o

One Q: Lets say you had an area both to wide and long to do in one go, what pattern would you use to tackle it?

Many many thanks.

If you have some thing to veneer that is both long and wide, I would start with the shortest side but it does not matter too much, as long as you make sure the glue is not too thick.
Also as you had done, keep the iron on but not to hot, so I would get the iron ready before starting too.

Ps I almost forgot to say :roll: , when you wet the veneer, wipe it with a wet cloth and dont wet it to much.
I hope thats clean
One more thing ( you have got me on a good day, as my brain is working today \/ ).
You can put stick under the veneer to stop it sticking to any drips of glue and also makes it easier to lift.l

 

[Paul Kierstead]

Ah, Try #4. Contrary to my plans, it was with hot hide glue. I wet the veneer and pressed it for a bit before applying. I did a small strip (about 2") at a time. This time, it came out much better, and I attribute that largely to the wetting. In fact, as I proceeded across, the veneer noticably dried out and most problems were on that side. There were a few bumps, and I used some water, a heat gun and the hammer to carefully reheat and flatten (as suggested elsewhere; the missing component was water in my previous attempts, it works much better with it).

I am pleased at the outcome so far, though I'll know the real story after scraping and trimming. There was still too many problems and it took too long to fix them, but another couple of panels that size and I'll have it down pat I think (for that size anyway). Many thanks!

 

[Colin C]

I am glad I could help as veneering can be a PITA if you dont know where you going wrong

I hope we see some pictures when its finished :roll:

 

[Paul Kierstead]

BTW Colin, the stick idea whould have been a great one I will use that next time....

 

[engineer one]

just like when you fit a large piece of plastic laminate in for instance a
kitchen :lol: :lol:

amazing how many different skills can transfer if you work at them :twisted:

paul :wink:

 

[Colin C]

But we still have not seen any pic's [-(

 

[Paul Kierstead]

But we still have not seen any pic's [-(

Ah, well, need to get home, scrape and trim. Bit of a time diff here. And our club has a meeting tonight. But I'll put em up, I promise. Well, if I am happy with it and don't go for try #5.

 

[Colin C]

If we see the pic's, it might also help us to help you
I will be waiting