How thick can a veneer be and still behave like a veneer?
I recently made a backgammon board. The game face is maple, purpleheart and lyptus, sawn to 1/16″, maybe 3/32″ in parts. It is epoxied to 1/4″ lyptus ply, and the whole thing is glued into the case.
It behaved pretty well at first. Then, while finishing I left all the windows open in the spot for a few days during very humid weather. The top has lifted off the substrate in a couple areas.
I realize I probably can’t fix this board, but I’d like to avoid the same problem on the next. I also want to stay away from a raised panel design.
Thanks for any help. I can post pics, if necessary.
Replies
Without knowing more, it's difficult to assess what went wrong. The thickness of your veneer is not the issue. I use shop made veneer that thickness and thicker all the time without problems. Some potential issues are:
Let us know.
Jeff
I cut triangles for the game face from 4/4 stock, then resawed veneers from that. After each slice was sawn from the block, I flattened the block by running though a planer. I couldn't get it planed without tearout, so I glued the torn out side to the ply.
Due either to my skills or tools, I was not able to produce perfectly even slices of veneer. I glued them to the ply with thickened epoxy, bad side down, weighted with 6 gallon bags of sand as clamps, then flattened as uniformly as I could with a hand plane. I used epoxy specifically to address the tearout and whatever uneven spots might have been created by my half a$$ed approach to shop made veneer.
I did not veneer the other side of the ply.
I'll attach a picture. My photographic skills leave something to be desired, but I hope you get the idea.
I am getting small areas of lifted veneer in one quadrant of the board. I moved it into the house yesterday, and it seems to have gone down some.
Is this thing doomed to tear itself apart, or will it just get these bubbles in wet weather?
Edited 3/24/2007 11:51 am ET by TXJon
It is very weird that you are having these problems.
It seems like you may have not applied your epoxy properly.
When you used your epoxy, did you apply a thin coat to both surfaces, then apply thickened epoxy over that prior to clamping? It's the proper way to apply epoxy so that it will fill the voids, and stick to the wood.
The only other thing that I cans see that may have happened is that the wood that you cut the veneer from had too high of moisture content, and is shrinking. Having just said that, I still don't think it would lift if the epoxy stuck it down properly. It is more likely that the parts would stick buy maybe split.
Hopefully you didn't use the epoxy that comes in the little tubes, and even worse than that, you didn't mix good epoxy improperly.
I'm not accusing you of anything, just trying to figure out what may have gone wrong. It is surprising how often woodworkers who aren't good chemists will add extra "hardener" to their mix, thinking that this will make the epoxy get harder. Actually the part called 'hardener" is really just a reactant, and adding extra just leaves a bunch of hardener that doesn't have anything to react with, which leaves a lot of unhardened hardener.
Hal
http://www.rivercitywoodworks.com
TXJon
I've read your response, and read the other responses from our comrades. Here's what you need to do.
Scrap using epoxy for veneering. It can be done, but is not the bonding agent of choice. Use a PVA glue, or plastic resin glue. Easier to work with, and in the case of plastic resin glue, much more open time.
Some will tell you working with veneer that is torn out and uneven is workable. I completely disagree. Stock preperation is almost assuredly the reason for the failure in your first try. You need to work on your veneer prep if you are going to continue to work with shop made veneer. I saw my veneer at 1/8", and drum sand it to an even thickness, about 3/32". If you don't want to invest in a drum sander, and I wouldn't if you're just a hobbyist, then you need to spend 50 bucks on a cabinet scraper like a Stanley #80, but I recommend the one from Veritas. It's just better. Use it to remove all your tearout. That means, if you have to start with thicker veneer and scrape more off to level it flat with no tear out, than just do it. The extra work the first time getting right means you don't have to repeat yourself after it fails.
Now that you have workable veneer, and the correct glue, you have to use a better clamping system than 50 lbs. or so of sand bags. You need to make a clamping sandwich with 3/4" plywood on both sides, with cauls stretching across, and lots of clamps. I'm no scientist, but clamps create a helluva lot more pressure than a sandbag does. My vacuum bag creates 1500 psi of pressure, and I leave the workpiece in for 24 hours.
Now, you absolutely have to apply veneer to both sides of your substrate. The good news is, you don't need to do all that fancy work to the unseen side. Just one sheet of veneer, same thickness as the other side, applied to the bottom side of the substrate.
Now you have a completely workable solution to the beautiful gaming board you are making, and it will last you the rest of your life, unless you run into my wife, who's a professional backgammon player, and she wins the board off of you. Then, you'll have to make another. The good news is, now you know how.
Post pictures of the next one when it's finished. I'll be waiting. Good luck, and don't skip any steps. You'll only be disappointed again.
Jeff
Thanks. I used sand bags because I was using epoxy, and wanted to avoid squeezing it too hard.
I can't avoid fussy work on the back side of the board because that is the outside of the case.
I would really like to have a drum sander, but at about $900, it's a little steep for me.
I'll look into the Veritas scraper, and save my pennies for that sander.
I've been at least thinking about this project for five years or so, a set back of a few more weeks or months is no big deal.
BTW, the cut veneers sat in the shop for weeks before I glued them, so I think they were as dry as they were going to get.
Next time, veneer both sides, better veneers, PVA glue. I'll get started.
Does your wife know where to get custom game pieces, maybe something in stone?
Thanks again.
There is a drum sander kit available for a couple hundred dollars. Do a search for it you won't have a problem finding it. It has been tested to sanding items to less than 1/32.
I came across the DIY drum sander. Have you used it, or do you know anyone who has? The price is right, but if it doesn't actually work I'd be better off saving those pennies.
I went to a Wood Shop weekend before last and seen it in opperation. I was actually very impressed with it. I have a brochure somewhere in my shop. I shall scan and upload it for you. Had it not been for the fact that i am currently moving my shop and do not want to move anything extra i would have bought it.
One thing you can do to avoid the whole sander/scraper/whatever issue is to surface the side of the wood that you are going to glue down, bandsaw the veneer off the board, glue the veneer to your substrate, then belt sand or hand plane the entire surface after gluing.
I have done it this way many, many times when gluing burl veneer to things. It works really well and you don't need the drum sander.
Hal
http://www.rivercitywoodworks.com
There are a few home made drum sander plans around. look on the various luthiers sites. Havent made one but doesnt seem too hard. The best I have seen used its own platten to true up the drum during assembly - a real boot strap effort.
here's one, but I have seen easier
http://www.mimf.com/archives/thickness_sander2.htm
Dave
If you are getting tear out when you plane you are probably feeding the wood against the grain. Try feeding it the opposite direction. Also if you are using a band saw to resaw ensure your blade is riding exactly in the center of your tires. Also for resawing use a 3 TPI blade to avoid sawdust backing into you cut and causing your blade off track.
TXJon
Not all is lost. A few things speak to me here.
You said you used epoxy to glue the veneers. I would not recommend epoxy as the glue of choice for gluing wood to wood. You would be better off with a PVA or Urea based glue than epoxy. It is so brittle when cured that the wood movement can break the bond. You can also thicken other glues like urea glues by using fine cellulose fillers. They are available in places that cater to people buying polyester resins. I think I once saw that they are also available at Lee Valley.
You glued to a substrate that has a grain direction. Check your failed areas. Does their grain run parallel (more or less) to the grain in the substrate? Remember that it is advisable to crossband veneers when gluing one on top of the other, i.e. the grain direction on the top piece needs to be perpendicular to the grain direction on the substrate, if you want to avoid long term problems like the surface veneer splitting as the substrate moves at a different rate to the surface veneer.
By the way, if you would have used a PVA or urea glue, you could have injected some glue and clamped the assembly together again and at least attempted a simple repair. Now what you can do is remove the delaminated pieces, clean off ALL the epoxy by scraping with sharp chisels and any other tool that you think will help, cut new pieces of veneer and glue up the repair. Good luck. JL
Edited 3/24/2007 3:49 pm ET by jeanlou
Well, thanks. Maybe it's hard to tell from the pictures, but I think it would be easier to start over and get it right than to remove part of the veneered piece and repair it.
It sounds like you are saying the glue is my problem, not the movement in the veneer. Is that right? Should I be able to get away with veneer this thick glued to 1/4" ply as a substrate?
Can I get away with not veneering both sides, seeing as the board is glued and rabbetted into the case? Would I do better to use 1/8" ply and veneer both sides?
Sorry for all the questions. It is probably obvious, but I am new to veneer work.
TXJon
Yes to both. The wood veneer is moving and the glue is too brittle.
If you want to do a classic glue up, you should be using thin veneers and glue to both sides of the substrate to balance the assembly. Since you are using thicker home made veneers, and the pieces are locked into a groove and are not that big, I do not think it is much of an issue if you have no backing on the glue up, though it is not by the book, so no money back guarantee on the work.
You should work on eliminating the tear out and find a way to glue a truly flat surface to the substrate. One way is to use an edge sander, or a belt sander set on edge to work as an edge sander to flatten one face, and then cut your wedge. The saw cut side is the face and the flat sanded side is the side that will be glued to the substrate. Sand the wedge block once again and cut another piece...and so on.
Once the glue up is complete and set, flatten the face. Try to glue up the veneers using a press or cauls and clamps. Sitting weights on the work is not the best way and once again, will not come with a money back guarantee for the finished product. JL
The biggest thing that I have found when cutting my own veneers is letting them dry. I know that you are usally cutting them from what is thought to be a dried board. But when slicing of the veneers releasing all the tension that is in the board makes them move. Also the inside of the board is wetter than the outside.
I always let my veneers sit for a few days at least. This will allow them to move and dry and do whatever they want. I never make my veneers more that 1 - 1.2 millimeters think. That is twice as thick as a commercial veneer. The reason for that is any thicker and it esentailly becomes a very thin board. ANd it will move and have the strength to move. But the thinner it gets the less strength it has to pull free or wrap your substraight.
http://www.kalafinefurniture.blogspot.com
Tex,
Given the situation that you had, I think that epoxy is the best glue that you could have used. It has good gap-filling strength, and doesn't need a lot of clamp pressure to achieve a good bond. As a previous poster suggested, the preferred procedure would be to "prime" the surfaces with straight epoxy, then, in a few minutes, recoat with another layer, maybe mixed with some (fine) sanding dust so it has the consistancy of peanut butter. Assemble and weight,or clamp. Look for some squeezeout all around.
All these woods are hard and dense. I wonder if the glue surfaces were glazed or burnished, by dull planer/jointer knives (You mentioned being unable to avoid tearout)? Epoxy works better if it has a "tooth" to grip onto.
So, I'm suspecting one of two things; either a starved joint, where insufficient glue was applied, and either soaked into the wood, or left voids in the spaces between adjoining pieces of different thickness-- or a poor bond, due to a too slick (burnished) surface.
If the delaminated areas are loose enough to pick up a corner, you might try injecting some more epoxy, and clamping the lifting corners back down.
Regards,
Ray Pine
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