Veneering over stave core

[Mark HortonMD]

Hello, this is my first post on sawmill creek and was hoping someone with stave core veneering experience could give me some advice.
The project is for 25" width counter tops.
My plan , glue up flat sawn poplar 6/4, veneer with 3/16" shop sawn (flat) cherry using original titebond pva , in vacuum bag.

Dimensional change for poplar = .0028
Dimensional change for cherry = .0024

Both species are currently 9% mc,

I am expecting these tops to shrink in width 1/4" by the end of heating season and mounted to cabinets accordingly. (3/8" drilled holes with fender washers)

reason for pva I'm thinking is so it can move, will UF glue be too stiff and cause cracking/ cupping?

Should I try to somehow dry the wood down to 6% and get it all glued up before it acclimates?

I don't want to use a super thin veneer on this project, or mdf substrate.

Any thoughts?

[John TenEyck]

Conventional wisdom says that if the veneer is thicker than 1/8" it acts like solid wood and will fight the core it's glued to. With 1/8" thick veneers I think your plan is fine, although personally I would use Weldwood Plastic Resin Glue.

As long as all your wood at 9% moisture is now at equilibrium with your shop I see no reason for future problems.

John

[Chris Padilla]

I'm with John. Veneer is 1/8" or thinner otherwise it's just (hard)wood and should be treated as such.

I'm sure you have your reasons for the 3/16" veneer but the thinner you go, the better you'll be in terms of movement.

Further, if you use something other than the poplar like MDF or plywood, you'll also be better off with the thicker veneer you want.

Or you could do your plan and everything could be fine...but it may not be. Rigidly connecting two different species of wood is tricky. Rigidly connecting veneer to not-solid-wood is less tricky.

[william watts]

I have built up veneer panels, but nothing of that size or thickness. These used a poplar core with poplar crossbanding and made a very nice flat panel. Should your plan have the grain of the poplar and cherry running the same direction it's possible to develop cracking and splits in the veneer, even if the expansion rates are nearly the same. My opinion, never tried it, just for that reason. Why risk it 1/8 popular crossbanding solves the problem, even if it is another step in the process. Why not use BB plywood for the substrate, 3/4in.glued togeather?

[Mark HortonMD]

Thank you for the responses so far,

I'd agree that yes glueing less than 1/8" thick veneer to a substrate that doesn’t move with rock solid glue would be a tried and true option.

The poplar is run with a glue joint and a cherry 6/4 piece at the end for the show ends alternating joints, its hard to explain, I'll post a picture when I get it to that point (reasonably convinced things will work)

The reason for going to this extent is to get a end grain where the counters end instead of a piece of tape or thin strip with the grain going in the other direction.

The thinner you go the better to lock the wood to a substrate that does not move, the proper glue stabilizes the wood into plastic in essence ? please correct me if im wrong

If both solid hardwoods with same coefficient nomatter the thickness face glued with grain in same orientation, with a glue that allows some flex of the wood in a +/- 3% moisture content swing, not considering all the variables of grain change and knots, it should act more or less as one piece of wood?

Would plastic resin glue tolerate stretching 1/4" over 25", then returning 6 months later to its original position?

[Chris Padilla]

The poplar is run with a glue joint and a cherry 6/4 piece at the end for the show ends alternating joints, its hard to explain, I'll post a picture when I get it to that point (reasonably convinced things will work)

Yeah, I'm not quite visualizing what you've got there so I look forward to you updating this thread when the time is right. How about a crude drawing?

The reason for going to this extent is to get a end grain where the counters end instead of a piece of tape or thin strip with the grain going in the other direction.

Yep, I think I follow you here. I did something similar with a tansu I built. Maybe there is something in that thread you'll find useful?

The thinner you go the better to lock the wood to a substrate that does not move, the proper glue stabilizes the wood into plastic in essence ? please correct me if I'm wrong.

Yes, that is pretty much it. In that tansu above, I shop-cut 1/16" walnut veneers and glued 'em to an double 5/8" MDF sandwich that was edged with 1/2" walnut to get a nice beefy looking panel that weighed a ton. Everything I did there has, so far, lasted just fine and that is going on 7-8 years now. I'm quite pleased.

If both solid hardwoods with same coefficient nomatter the thickness face glued with grain in same orientation, with a glue that allows some flex of the wood in a +/- 3% moisture content swing, not considering all the variables of grain change and knots, it should act more or less as one piece of wood?

So if you glued your (fancy) cherry veneer to (not so fancy) cherry hardwood, then I would expect them to pretty much act as one piece of wood. I've done this plenty of times with birdseye maple veneer to plain maple and so far so good there...going on 5ish years. You do keep mentioning a glue that flexes. For the most part, I think you'd want one that glues rigidly. Some folks have noted PVAs "creeping" over time and some use PVAs all the time in veneering and seem fine. I prefer to use a more rigid glue and not PVAs for veneering.

Would plastic resin glue tolerate stretching 1/4" over 25", then returning 6 months later to its original position?

I didn't specifically use a 'plastic resin glue' for my tansu (see the link for what I did use) but I did use one that dries hard as a rock and all I can say is that things are just fine for however much it has moved...which isn't much due to the MDF core and very thin veneer. I'm guessing the glue has held the veneer firm and not allowed it to budge at all. In my maple to maple, veneer to hardwood application, I used the same glue...same results...all good so far.

[Mark HortonMD]

With your advice, I'm changing my original thought of using solid poplar for my substrate, a countertop in this application doesnt need that structure as if it were an entry door. That takes out a lot of variables and steps, with wood movement, glue, and moisture content. Time to tune up my bandsaw to make thinner slices.
Thanks, John, Bill , Chris

[Chris Padilla]

Where will the countertop go in your house, Mark? High moisture environments and wood countertops that tend to get abused with substances tend not to do well over time. Bathrooms could be a similar although perhaps a less abusive environment. My tasnu lives near the front door so it is fine. The other item, a fireplace mantle, is also doing fine with the birdseye veneer on solid maple despite the seasonal heat from the fireplace.

So your next thread will be on tuning up your band saw for slicing veneers, right?! Also, you'll wonder what the best blade to use might be.

[Wayne Lomman]

I would definitely use a high strength glue. PVA just isn't up to it. Cheers

[Gerry Grzadzinski]

As long as you "veneer" both sides, 3/16" veneers over poplar should just act like solid wood, and the faces should expand and contract together. In this case, veneer thickness shouldn't matter.

If you're using a plywood or MDF substrate, I've always read that 1/8" should be the max thickness, because the faces will move more than the core, and if they are too thick the movement can break the glue joint.

Either way, I'd also recommend something with a more rigid glue line than PVA.

[Chris Padilla]

Gerry has a good point...one always wants to balance a veneer glue-up such that both sides of the substrate receive the same wood of the same thickness.

However, I think this is mostly to keep the glued up panel flat and coplanar. Movement of different species still exists only now the wood in the middle is getting it on both sides instead of one regardless of the movement being identical. It still doesn't sound like a good situation to my thought process mixing wood species unless one of them is, indeed, a veneer. Further, the grain of both species is likely to be in the same direction.

Think of it this way: you are kinda making your own plywood...kinda sorta. But the plies in plywood are rarely, I think, more than an 1/8" plus they have the grain orthogonal to each other plus all that glue and now you see why plywood tends to not move as much as solid wood. Finally, the faces of the plywood are even thinner than the core plies and this is for two reasons: cost of thinner ply of 'show' wood and to make sure it moves very very little.

[Mark HortonMD]

Well I didn't want to go about making my own plywood, but wanted a thick bookmatched veneer/solid wood. For hundreds if not thousands of years it was glued over solid wood substrate, and still is today over quarter sawn stave core for entry doors. Do you think a custom $10,000 walnut door is solid? Do you think the veneer thickness is less than 1/8 . I ran across a newel post that was poplar stave core with 3/16 oak. But for this project I'm taking everyone's advice and going just under 1/8 cherry over mdf, with uf glue. After adjusting bandsaw it's slightly improved cut, blade is grizzly g5313, it cuts just better than a woodmizer Sawmill! Chris these tops aren't for myself, but I will be making one for myself soon that is stave core with undermount sink to see how things endure. Thanks for all the advice, I'll post pics when completed

[Mark HortonMD]

2 of 3 tops, 3/32" +/- cherry, 1" mdf glued to 3/4 vc plywood, 1 3/4" solid edge. Just thought Id post these to show what I went with after some advice from SMC.
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[Jeff Duncan]

Ok silly question.....but why didn't you just glue up a solid cherry counter? Cherry is a relatively inexpensive wood and gluing up a solid top would give you a higher quality more durable product, and be so much easier to fabricate....ie. less time and labor. Looks like you succeeded in your mission, just might be worth considering the simpler, (better?), solution if you come across this again in the future

good luck,
JeffD

[Mark HortonMD]

Jeff, very true I've done many solid tops flat sawn and quarter sawn. 2 reasons, one is to not have to allow for movement these get shelving units installed on top, second is most times people want tops out of walnut and it's getting expensive to make 2" thick solid. So this is a first attempt at how I will be doing walnut tops in future, it wasn't that much more labor especially if I can get my bandsaw cutting right, ordered a lennox ct blade should be here today. I'm fortunate enough to have a wide belt to help with sanding.
Overall I think it's worth doing it this way being able to book match grain , a solid edge, thicker veneer, no movement