Better Bond Problem or Something Else?

[John TenEyck]

I had never used Better Bond Cold Press Veneer Glue until about 4 months ago. Since then I've used it twice. In both cases I glued 1/16" shop sawn veneer; in one case 8 - 9" wide birdseye maple over a solid oak field in a repair job, in the other case is was 4 - 5" wide rift sawn white oak over BB plywood. I veneered both sides of the substrates. The birdseye maple top was made in the Summer, the WO table top only about a month ago.

Fast forward to about a week ago. The exceptional picky lady I made the WO table for called to say that she could some lines in the top, maybe where the veneer was seamed. Uh oh. I asked if there was a definite gap and she said something like "No, but I think I can see where the seams are." OK, I said, I'll stop by when I get a chance.

Today I was at my friends for whom I repaired the birdseye maple top. I inspected it and, sure enough, you can see where the veneer seams are, tiny little gaps over most but not all of their length, too small to get your fingernail into, but you can see them, maybe as wide as the thickness of a sheet of paper.

My shop was at 50% RH when I veneered the birdseye maple top, and the wood had been in my shop for months and measured around 8-9% MC as it should have; the house where it is now is around 35 - 40%. In the case of the WO table the difference can't be any more than 10%. Anything is possible, but it's hard to imagine that little change in RH is responsible, though I'm at a loss to come up with another explanation. These two tops are the only two times I have used Better Bond glue. Two tops, same problem with both. I've always used Weldwood Plastic Resin Glue in the past and never had a problem like this.

Has anyone else had a similar problem with Better Bond? I don't want to falsely accuse Better Bond for being the root of the problem, but it's hard to explain what else might be causing it. If it's not the glue, what is it?

John

[Mel Fulks]

I've never used it but it is advertised as a gap filling glue that has ground up nut shells in it . For work requiring adjoining pieces ,something non gap filling might be better. Give the company a call.

[Mike Henderson]

This is just a guess because I'm not familiar with Better Bond. If it's a PVA glue I can see two issues. The first is that PVA glues are water based so the veneer will absorb water from the glue. The second is that PVA glues can creep.

BirdsEye maple veneer is rotary cut (face cut in lumber) so it tends to expand and contract a lot more with changes in moisture than other cuts (riff or quarter).

I use PVA glue with commercial veneer all the time, without problems, but commercial veneer is 1/42" thick. Try some urea formaldehyde glue on your next job. It's a water based glue but it dries hard, with essentially no creep. ProGlue is one that I've used. The problems it has is getting it mixed smooth (no lumps) and applying just the right amount to the substrate. I find PVA easier to use - more forgiving.

Mike

[Andrew Hughes]

My guess from a thousand miles away would be glue creep.If it is you should be able to see the glue up close with a magnifier.I have never used the particular glue. But I have had glue line show up in my work from titebond and such.
I do feel for ya having work comeback is a pain in the butt.Andrew

[John TenEyck]

Thanks for the replies so far. To clarify, the veneer was shop sawn, by me, to 0.090" then drum sanded to 0.065". Birdseye maple and rift sawn white oak. Better Bond Veneer glue is a PVA glue, a lot like Titebond Cold Press Veneer Glue. It is supposed to be rigid once cured, like the UF glue I typically use (Weldwood Plastic Resin Glue). I am definitely going back to the UF glue, two problems in a row is enough evidence for me that the problem stemmed from the Better Bond glue. I'm just trying to understand how it happened. I don't think the relative humidity changes were great enough to cause it. That leaves me thinking Mike's explanation might explain it - the veneer swelled from the moisture in the glue, and the glue has allowed it to creep as it dried out over the next several weeks. The fact that the veneer was 1/16" thick in contrast to the 1/42" thick commercial stuff might be contributory to the problem as it will absorb and hold more water; the thinner glue would dry out much quicker, perhaps before the glue fully cures, resulting in less future creep.

Any additional thoughts, anyone?

Thanks,

John

[Richard Coers]

Did you glue the shop made veneer parallel to the solid oak, or perpendicular to the oak? How wide was the oak field? Did you check the moisture level of the Baltic Birch? Was it from a quality supplier or Borg? I'm thinking substrate movement.

[Mel Fulks]

The Weldwood glue is mixed with water ,and yet, there is considerable agreement among us that is not a problem . I have been told by makers of PVA glue that IF YOU DONT ADD WATER YOU YOU WILL NOT HAVE A PROBLEM WITH WATER. I have found that to be true. An addition of 5 percent water to PVA makes a huge difference in viscosity. I don't have any info on what adding nut shells does to it , but I'm guessing it might be too thick ...unless you add water. I also think "creep " is an unfortunate word for "flexible". Modern PVA glues do not creep in the same sense that white glue does. White glue can actually cause a misalignment between two pieces of glued metal after filing flush . Yellow glue won't. I relate this to my post the other day about not caring about the science of wood movement, I can learn what works a lot easier than I can learn WHY it works.

[Mike Henderson]

Regarding a water based glue, I've seen many times that the amount of water in the glue can have a serious effect on the glue up. For example, take a piece of 1/4" MDF and glue veneer to one side using a water based glue, such as PVA. When you take it out of press, the MDF will be flat, but in a short time you'll find that the panel is bowed into the shape of a dome. Then set the panel in the sun, with the dome toward the sun and you'll find that the dome decreases quite a bit, but usually not to fully flat.

The reason - to my mind - is that the moisture from the glue causes the MDF to expand on one side. The side not veneered does not expand (or does very little compared to the veneered side).

I don't know why the dome never fully disappears when you put the panel in the sun, but my guess is that the MDF simply does not go back to it's initial state after being wetted.

I never tried it, but one experiment would be to mist the non-veneered side before putting the panel into press. It'd be interesting to see if that reduces the dome effect on the veneered side.

Mike

[Dan Lee]

Might have missed it but how did you prepare the veneer edge seams. We're they jointed and glued prior to pressing with BB to the substrate?

[Mel Fulks]

I have noted that too, Mike . Especially in the case of something like a stave core door stile . I do find it curious that in the case of furniture veneering there seems to be more reports of problems with PVA than UF and I can't imagine that PVA has anywhere near the water of of UF which we know is often used pretty thinly mixed. I can only conclude I would not use the glue that John used after reading of his experience . I dislike the use of "creep" not as a self appointed word expert but simply because I think it is confusing to someone new who might read in old media that "the new yellow glue won't creep like white glue". I can remember when some old timers finally dropped everyday use of hot glue and switched to yellow because of that improvement.

[John TenEyck]

The birdseye maple was glued parallel with the oak field of the table, just as the original veneer had been. I've seen arguments that veneer should be glued cross wise, others that say parallel over a solid wood field. The original was parallel, and that's the only way it would look correct, so that's what I did. Here's what that top looked like when I returned it to the owners. You can see where one of the seams is; nice and tight.

IMG_9465.JPG

I didn't measure the MC of the BB plywood. It had been in my shop for many months, maybe a year, so I didn't feel the need. I bought it from Rockler. If the MC of the BB plywood had been higher than my veneer it would have pulled the veneer seams tighter as it dried this Winter. If the veneer was higher, then gaps might be expected. Let me just leave it as saying both the plywood and the WO had been in my shop for many, many months, and my basement shop is temp. and humidity controlled.

I've never edge glued veneer sections together, although I know some people do with the thicker veneers like I used. I jointed them so they fit together tightly, then used cross pieces of gummed veneer tape, followed by a strip of gummed tape the full length of the seams. I'm not adverse to edge gluing if that will help, I just fear that it might cause problems with the veneer not staying flat, or some other problem, before I even glue it down. What do others do?

Thanks everyone, I appreciate your comments.

John

[Dan Lee]

Yeah on thicker shop made veneers I joint the edges, draw the seams together with wide painters tape, fold them back spread glue on the edges with my finger then lay it all flat and weight down the seams to keep the pieces flat and even. I later use a scraper to clean off any squeeze out before pressing to the substate. Ihave used BB a few times without problems, though I prefered UniBond 800. Believe I learned this from David Marks vids.
i wonder if your seam pulled open a little at the top sort of a V shape?

[Kevin Jenness]

Several issues come to mind. With the birdseye over solid rift oak, the two materials are going to have different rates of movement with changes in relative humidity. Add in the relatively soft pva glueline and the fact that the veneer joints were not glued, and the observed hairline cracks should not be surprising, even though the RH change is as little as 10-15%. The same issues are at work in the other top, though the relative movement potential would be less given that the baltic birch is a crossgrain laminate. It is generally considered good practice to run the face veneer at right angles to the underlying veneer. With veneer over solid, it seems parallel grain direction should be ok, but as you have seen there can be problems with different species and orientation. (Did you veneer and finish the underside the same as the top surface?) The thicker the face veneer, the greater the stress and potential movement at the surface and the more it tends to behave like solid wood. A stiffer glueline and glued edge joints would help. There are pva glues with less creep than others, but generically urea formaldehyde and epoxy glues are stiffer.

Although it is an extra step, I like to edge glue thick veneers into a sheet prior to layup. I find it easier to handle than a taped assembly,plus I am more confident the joints will not open up. Another approach is to tape the leaves together and use epoxy which will wick up into and adhere the edge joints in a vacuum press.

[John TenEyck]

I contacted the supplier I bought the Better Bond Cold Press Veneer Glue from and he told me that it is not suitable for the thick 1/16" shop sawn veneer I used. I saw no reference to this on his extensive website.

For my next panels, I will edge glue the veneers as several have recommended and I will go back to Unibond 800 as it has no water in it.

Thanks for your input. Much appreciated.

John

[Mel Fulks]

Well thanks for letting us know ,John . I've never heard anything negative about Unibond 800.