Boards cupping with glue-up

[Bruce Mack]

I'm making a 16 X 24" serving tray using curly oak as the bottom. I have a 1' thick 5 1/2 inch wide board that has acclimatized in my shop >10 years. I tried to get 4 boards from it but ended with three usable ones of different thicknesses. After planing and some replaning because of tearout I had 3 boards with good figure. They were ~1/8' thickness and lay flat on the 1/8" Baltic birch which was to be the substrate. The edges met neatly with no gaps. I was happy to have something that even with the sides would not be overheavy. After rolling the PVA glue onto the birch and laying the oak pieces I had rapid cupping, with convexity of the oak surfaces in contact with the glue. I weighted the panel with a granite surface plate and a few pieces of steel in the hope of some planarity when the glue-up dried overnight. It has remained a washboard after my halfhearted heating of the panel with a heat gun and further compression pressure. I plan to resaw more boards a little thicker and with a new blade.The additional thickness will give me a little wiggle room to correct tear-out, but no assurance against cupping if a water-based glue is used. I'm thinking slow set epoxy. Polyurethane glue is messy and the spritz of water may itself cause some cupping. Am I missing something I should consider? I do not have or wish to buy a vacuum system or use toxic adhesives
The extreme separation is partly the result of my unsuccessful effort to salvage the oak. It469416469417 was ugly before that effort.

[Andrew Seemann]

As you suspect, the water is causing the oak to expand. The plywood can't expand, or at least not as much, due to the cross ply.

I'm not sure if you can make that design work, usually a veneer would be much thinner, so the substrate can overpower the the veneer. For your tray, the oak is the same the thickness as the plywood. Even with a non-water base glue, it will still have problems.

In our climate (wasn't it 50 degrees warmer a couple days ago?) the oak and plywood will forever be at war with each other, unable to agree on what size to be, and forever twisting, cupping, and trying to separate. Even if you bumped up to 1/2" plywood, I think you would still have problems with 1/8" veneer.


As an aside, one of the traditional ways to cut stone, since you bring up granite surface plates, was to drill a series of holes in the stone, pound in wood stakes, and then pour water on the stakes. The pressure from the expansion of the wood was so strong, it would cause the stone to crack along the lines of holes. Just letting you know what you are up against with the power of expansion in wood:)

[Richard Coers]

I can't figure out if you only glued the oak to one side or both. You have to do a balanced layup so both sides are equal. I was taught that any shop cut veneer has to be around 3/32" from the boards and then finished to 1/16" to act like veneer. Go thicker than that and it acts like solid lumber. There is more movement with flat cut boards than quarter sawn and rift sawn.

[Jim Koepke]

Will the finished panel be held in place by slot?

It might be possible to put it together without glue or just a dab of glue in the center.

jtk

[Kevin Jenness]

That is a pretty thick veneer, especially for flat cut oak. 3/32" is about as thick as I use on a substrate that restrains the veneer.

To get a flat result you need to veneer both sides and get the glue and clamp pressure on before the veneer has a chance to expand and curl. A glue like Unibond 800 or epoxy with little or no water can help. A thicker substrate or thinner veneer would help.

You can saw your boards thinner and run them through a thickness sander with no worries about tearout. If you can resaw them cleanly enough you could lay them up with epoxy and sand them afterward.

To do this over with epoxy and weights you need a waxed flat base and top caul thick enough to spread the pressure evenly. Be sure to sand the mating surfaces with 80#. Pull the joints together with clear packing tape and run tape along the seam to prevent squeezeout. Do a dry run to be sure everything lays flat.

[Lee Schierer]

If I read your post correctly you resawed a board to get four pieces, but only ended up with three that were usable. Then you planed additional material off the cut side to get them acceptably flat. Then you applied glue to one side to bond it to the plywood.

A couple of suggestions. Whenever you resaw any piece of wood, weight, stack and sticker it to allow it to adjust to the ambient moisture for a while (several days-week) to insure it stays flat. The internal moisture level changes much more slowly than the exterior. Since we just went from fall, which is usually damp to winter where our heat system dries out the air, there was an ambient moisture change in your shop.

Second thought. When planing wood surfaces, it is always a good idea to remove equal amounts from each large face area whenever possible. This helps reduce the cupping.

Since we know that moisture from glue causes swelling, it would have been advisable to dampen the exposed side at the same time with distilled water to equalize the wood.

[Bruce Mack]

Thanks everyone.
Lee - in my usual slow mode, I let the boards lie in my shop for about 3 days before the glue up. I have seen slices from unseasoned pine curl like a potato chip. While the PVA released some demon, I suspected no problem before the glue-up. When I noted the cupping, I wish I had spritzed the exposed side then. I'll keep this in mind.
Kevin - I should have changed the blade before resawing. I had not used the bandsaw for that task in a long time. I'll try thinner next time. Not having a thickness sander, I'll just take the slices and lay them up with epoxy, scraping and sanding afterwards. Great suggestions in your last sentence.
Jim - I am trying to do a one-off of a designer tray as a gift. I haven't thought about the sides for this piece. Google "Michael Verheyden oak serving tray with hammered bronze handles". Mine will be minus the bronze and, sadly, minus the craftsmanship.
Richard - I glued the oak to just one side. The Baltic birch stood up to the stress like armor plate with no rippling. I think I did not apply enough glue with the roller as the glue had started drying. I should have used Titibond Extend to allow myself time.
Andrew - it does look like warfare (and my ineptitude). It's funny about Minnesota climate changes and wood splitting stone. Maybe my recipient, also in Minnesota, will like her hygrometer tray that moves with the seasons.
To everyone - thanks for the unexpected (by me) observations! There's a lot to think about. I'll post if I ever finish this.

[James Pallas]

Age old thing. Thinner veneer and lots of pressure. Just looking at a veneer press is scary. I know vacuum works for thin veneer but a press measures in tons not pounds. Thin your veneer and try again.
Jim

[Bruce Mack]

Age old thing. Thinner veneer and lots of pressure. Just looking at a veneer press is scary. I know vacuum works for thin veneer but a press measures in tons not pounds. Thin your veneer and try again.
Jim
I'll do that. Thanks.

[Andrew Seemann]

Hi Bruce,

You can run the veneer through my thickness sander if you want. I'm just a few miles south of you in Mound. PM me if interested.

[Robert Engel]

The veneer did what all veneers do. I think the problems started with you not using it right away and not clamping it.

You don't need a vacuum press. Make some platens, 2 sheets of 3/4 MDF top of veneer/1 sheet under plywood, stout cauls (I would use 2x4's) space about 6" apart. Clamps all along the edges about no more than 4" apart. If the panel is wide cambering the cauls is a good idea.

Next time, go straight from resawing to gluing.

[Bruce Mack]

Nothing can stop an old man with time on his hands. Although I may eventually put a new blade into my Delta bandsaw and saw thin veneer, I still see my misadventure as a work-in-progress. I first glued the entire periphery of my panel to the Baltic birch by squirting PVA glue into the gaps and using spring clamps to create contact. These small clamps when appropriately spaced apply considerable force. Then, recalling how I used to dry-mount photographic prints with an iron as well as an article on applying veneer pre-coated with PVA glue using heat to activate the dried glue, I bought a steam iron and tried to glue the long edges. A lot of heat (with steam to avoid scorching the boards) worked briefly but when I removed the granite surface plate used to apply pressure I saw that the edge gluing still had gaps. Moreover the edges still lifted from the plywood backing. I flipped the panel and did shallow rip cuts to enlarge the gaps to slightly less than 1/4". Next I will squirt glue into these gaps and press the edges to the baltic birch using cauls with a slight convexity that I made yesterday. They are sections of a 2x4. The cauls will be held with f-clamps from hell, two 12" Piher Maxipress F piston clamps which arrived yesterday in a box weighing 13 pounds. I'll do one joint at a time, thinking it will make setup easier and a lot cheaper. The clamps are self-indulgence and overkill but they are beauties https://youtu.be/I5Gbi_DXOUY.
If the glue-up holds, I'll inlay the channels with either quarter-sawn oak or ash.
470063

[Bruce Mack]

I eventually got a flat panel by crossbanding ash strips on the back of the thin Baltic birch to remove the cup and some other sleight-of-hand to deal with longitudinal bow. I just saw Luke DuPont’s post “Oh hey, wood moves!” but I think I’m spared by the interposed thin plywood. Also my wood had already moved and I hope that’s that (the power of magical thinking). When I cranked down on the cross bands at each end I heard “crack.” I have a few narrow splits at each end that follow the figure of the curly oak. I think that epoxy dyed black will make a neat accent. Perfect is the enemy of good, maybe. The wood still has to be sanded and cleaned up, complementary strips have to be inlaid, everything has to be stained and Tru-Oiled, and the frame of the serving tray has to be made. This can be fun when you’re not doing it for a living.

[Tom Bender]

The adventure may continue when you stain. There may be adhesive in the joints and cracks and soaking thru that interfere with the stain. If you seal first it should help but then you will be coating instead of staining. Practice if you can on similar stock.

[Bruce Mack]

[QUOTE=Tom Bender;3173038]The adventure may continue when you stain. There may be adhesive in the joints and cracks and soaking thru that interfere with the stain. If you seal first it should help but then you will be coating instead of staining. Practice if you can on similar stock.[h hi Dr./QUOTE]

Thanks, Tom. Your comment prompts me to think harder. Glue creep under cauls has plasticized some areas. I’ll go after what I see with card scrapers followed by sanding of the whole surface. I hope to locate subtle areas with paint thinner. I’m thinking of Zinsser Clearcoat with amber liquid dye added followed with pumiced TruOil for surface protection. I will try this first on cut-offs.

[Bruce Mack]

The surface looks good and the board is flat after scraping and placement of oak strips to fill the 2 channels. As you can see I have varying gaps as wide as 1/2 mm. They are unacceptable. I want them to be uniform and no wider than 1 mm. if possible - shadow lines. I can't rout these. My tired brain says I can buy a cheap straight edge (which I don't have) and clamp it along the line, then score with a marking knife or a wide chisel.
I'll fill this with black CA glue to make a nice uniform accent line. Does anyone see alternative ways of doing this?

[Bruce Mack]

I could post only the picture showing the best segment of inlay. Here is the worst.

[Bruce Mack]

No method I tried worked so I removed the oak inlay and replaced it with cherry. There is still a glue line, perhaps more acceptable adjacent to the darker wood. I'll have to decide whether shellac and Tru-Oil or some other finish. I need to make a frame for the serving tray and would like to try ebonizing it with India ink. I have a quart bottle and I'm armed with a couple of YouTube videos. Of course I'll do samples before proceeding. I'd like not to use oak, as open pores would be a problem. Has anyone done ebonizing with ink or dye? Were you satisfied?

[William Fretwell]

Lee’s last paragraph is so true, what you do to one side you must do to the other, wetting the wood face would have helped, at least short term.

At this point you have doubled the joint lines, torn up the bookmatch, added more wood underneath and now want to route something?

It seems that using a little more oak at the outset, forgetting Baltic birch, would have been so much better.

[Bruce Mack]

Lee’s last paragraph is so true, what you do to one side you must do to the other, wetting the wood face would have helped, at least short term.

At this point you have doubled the joint lines, torn up the bookmatch, added more wood underneath and now want to route something?

It seems that using a little more oak at the outset, forgetting Baltic birch, would have been so much better.
This was my first attempt at veneering, William. I made a lot of errors and I tried to rectify them. Stubbornly I stayed with the original panel and it is now quite flat. I think it will look very good even with the discontinuity when lightly stained and surrounded with an ebonized cherry frame. In this case I think the misadventure turns out to have been a positive experience for me.

[Bruce Mack]

Every critique was right. Too thick veneer and improper technique. I'll recount the end. As I scraped the board I saw outward bulging of the cherry strip(s). They had thinned out so much that just finger pressure could deform them. I removed them and saw 2 "salvage" options. I could redo the inlays or I could pour amber colored epoxy into the channels and clamp the board flat while it set. This would assure that the board would remain flat and not deform with humidity changes. I chose epoxy and colored it nicely with a few drops of TransTint. It looked great when I mixed it but never set, leaving a sticky mess. I'm sure that I correctly maintained the 2:1 ratio of this System 3 product which I had successfully used just a couple of months before, so I think that the color additive was the cause. I had not made a test batch and this failure is entirely on me. I put a new blade on the bandsaw and I'll try to cut 1/16" veneer and apply it to both sides of the 3/8" baltic birch before the hand scraping and sanding. I fully expect failure again but I'm reconciled to it. Enjoy the photo.479846

[Ted Martens]

Bruce, I've used this product before, and was very happy with the results: https://toolsforworkingwood.com/store/item/LW-AMIS.XX
It was on white oak, the appearance was striking when finished (Watco finish on that one). They have it in both alcohol and water based formula.

[Bruce Mack]

Thanks, Ted. That's good information.

[Richard Hutchings]

Wow, this has been a learning experience, for me and you. I think I'll avoid any such thing and stick with solid lumber.:o

[Bruce Mack]

Wow, this has been a learning experience, for me and you. I think I'll avoid any such thing and stick with solid lumber.:o
It is funny to me now, Richard. Unknowingly, I tried to re-invent a process that is ages old. There is a line from Stephen Leacock, "He flung himself from the room, flung himself upon his horse and rode madly off in all directions."

[Christopher L Everett]

A furniture restoration trick I've seen with veneers is to apply PVA glue to the veneer and the substrate, let it dry, and then use an iron to melt the glue and get the bond. I don't know how well that would work on 3/32" thick veneers.

[Bruce Mack]

A furniture restoration trick I've seen with veneers is to apply PVA glue to the veneer and the substrate, let it dry, and then use an iron to melt the glue and get the bond. I don't know how well that would work on 3/32" thick veneers.
You are right. 3/32 is too thick and also not necessary as I can scrape and sand thinner veneer safely. I just tried dry PVA with a self-cut piece of softwood veneer. It has held well at the edges and did not scorch with brown paper between the iron and the veneer. My bandsaw blade is a 3 tpi Olson which leaves small serrations but when i do this "for real" I will face joint before each cut so as to glue smooth to smooth surfaces. I hope the technique works for me, as wet clamping and cauls require more finesse than I can muster and I don't want to try/buy vacuum bagging for a one time project.

[Jim Koepke]

My bandsaw blade is a 3 tpi Olson which leaves small serrations but when i do this "for real" I will face joint before each cut so as to glue smooth to smooth surfaces.

There are two tricks that have helped me reduce this problem.

One is a zero clearance bandsaw insert. Search term > zero clearance bandsaw insert < and you will find a lot of sources.

Second is some bandsaw blades have too much set, imo. With two metal plates in my vise the blade is carefully fed between the plates and is clamped on a few inches at a time to decrease the set.

These both help even with a coarser blade.

jtk

[Bruce Mack]

This has been going on for more than a year and a half. The project went off the rails because I didn't understand veneering, and initially used way too thick boards as veneer. Then, using bandsawn and hand-scraped 1/16" oak veneer, I tried the iron-on method with PVA glue. Disaster. The tray now is edge-glued 9 mm boards, again sawn from my own stock, ebonized with India ink, and glossed with Tru-Oil. The frame is cherry with a shellac finish. Soon I'll be driving to Alexandria, MN to hand it over. I have loved every minute of this project because it was done for dear friends.

[Jim Koepke]

Looks great Bruce.

jtk

[Charles Guest]

Glue it up thick, then process the panel to thickness as a unit a little bit at at time, over several days while you work on the rest of the project. Take material off both sides, keeping both sides flat and out of wind as you approach finished thickness.

[Christopher Charles]

Fabulous outcome and the hard-earned knowledge makes it all the sweeter. I'm sure your friends will cherish it.

Best,
Chris

[Bruce Mack]

Thanks, Chris!

[Lee Schierer]

Very nice final out come. Just a suggestion. When I make trays of a size similar to your tray, I make the bottom from solid wood 1/4-5/16" thick. The only glue is on the board edges so much less chance of moisture issues. Unless you plan to carry blocks of steel or concrete blocks on the tray the thin bottoms are sufficient strength.505311505312