Having problems first time veneering

[brad hays]

I've got this unusual project going on where I'm trying to produce what I'll call veneer wafers. I'm getting raw veneer from mbveneer.com and the goal is to back it with something very thin for support and to have it come out of the clamps perfectly flat, and as thin as possible. Instead of using the pricey stuff I'm first practicing with maple veneer from Woodcraft and using backer from Flagg that I've been told is phenolic, if anyone is familiar with that company; Wilsonart just bought them.

So last night I mate up some .025" backer (pictured below, about 1/3 the thickness of the quarter) with some .020" maple veneer using Unibond800 modified urea resin glue in my newly arrived (!) vacuum bag press. The glue was spread with a 1/16th notched glue spreader, so not too thick but it definitely could've been thinner. After pressing overnight it comes out this morning and immediately curls, and gets more curled with time. The obvious first change in this process to see if I can get the veneer flattened would be to veneer both sides of the backer, which I'll be doing tonight. I got 4" glue roller along with the vacuum bag press so I'll try that out tonight instead of the glue spreader and see what happens. I'd say the glue will go on quite a bit thinner using the roller.

So my question is...what other methods and materials should I look into to produce this ever-elusive veneer wafer I'm after? I don't have any experience using rubber cement but if a form of that could be evenly applied with maybe a spray gun or something I think that might be a process to explore.

I'm all ears.

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[Paul F Franklin]

Haven't done a ton of veneering so others here know better than me, but my two cents: Veneering the back will help a lot. Probably enough. Another option is to skip the backer and make 3 ply plywood using three plies of the same veneer, with the middle piece cross grain. I guess the middle piece could be a different veneer, but why bother.

[Maurice Mcmurry]

Putting the same veneer on both sides of the backer is a good idea. Alternating the grain a little or a lot could help too. A long clamping time and some warmth might help. Office and school type rubber cement is not permanent. Contact cement like formica glue is permanent but remains rubbery. I hope you are making roundtuits. If I had a pocket full of those I might be able to get something done.

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[Mike Henderson]

Veneer front and back AT THE SAME TIME and with the same glue. Usually doesn't have to be the same veneer but with really thin stuff like you're working with you may have to put the same veneer on both sides to get balance.

Mike

[Don Stephan]

Does Certainly Wood still carry thicker veneer?
Try a 3 ply, same species and grain type (quartered, flat, figured, . . .) with the middle layer cross grain to the outside veneers, which are oriented the same.

[Richard Coers]

All veneering needs to be balanced. You have a core and a layer on both sides in the opposite direction if everything has a grain. Eliminate a layer and you get a potato chip that curls based on the humidity. In fact you can make a wooden hygrometer by doing that. https://www.youtube.com/watch?v=qHcdlhw70LU

[Mark Leifer]

Wait, I just saw that you posted the same question on LumberJocks. Did you dislike the advice you got here?

[stephen thomas]

I'll pile on :)
What the other guys said above - balanced construction!

You did not ask, but i sure prefer pressure bag to vac bag, any time it fits.
Higher force, easier-faster, more convenient.
Easier to use heated platen.
Maybe that's just me.

No, it is not likely a factor for your app.
Balance is.
Like so much in life!

smt

[John TenEyck]

You can back only one side if you use epoxy, even yellow glue if you let it dry between cauls. You don't need a thick backer either. Plain Kraft paper will work for small projects like yours with no problems. I've made paper backed veneer from shop sawn veneer that I sanded to 0.025" and applied Kraft paper with TB II. Into the vacuum bag for an hour, then clamped between MDF cauls overnight. They were nearly dead flat. I applied them to Melamine with contact cement. I see them every day. 5 years, no issues.

John

[Richard Coers]

You can back only one side if you use epoxy, even yellow glue if you let it dry between cauls. You don't need a thick backer either. Plain Kraft paper will work for small projects like yours with no problems. I've made paper backed veneer from shop sawn veneer that I sanded to 0.025" and applied Kraft paper with TB II. Into the vacuum bag for an hour, then clamped between MDF cauls overnight. They were nearly dead flat. I applied them to Melamine with contact cement. I see them every day. 5 years, no issues.

John
Glad it worked for you. 2 veneer things I would never use when I had a business, paper backing and contact cement. It introduces one more glue line and contact cement doesn't work well if the customer ever shut down the climate control to go on an extended vacation.

[brad hays]

Thanks a ton for all the advice everyone. Learning a lot from this thread.

Hey there stephen (or anybody really), what is this pressure bag you mention? I just got a vac bag but the pump isn't that great and it's fiddly to use. I was thinking of returning it in favor of the table top system (functionally similar to the vac bag) where you have a large hinged framework mated with a sheet of vinyl that you just raise and lower on the table. The table top would be your platen. Looks much easier than this bag thing although more expensive if you buy it rather than make your own. And a heated platen? I'd like to hear more about that too.

And Mark, yes I posted at another forum. I like to get my question in front of as many people as possible.

[Kevin Jenness]

Brad, if you explain how you plan to use these laminates it would be easier to advise you. If you just want to flatten rippled veneer that can be done with flattening solution and pressing repeatedly with dry paper, no backer required. If you want to make a stable flat laminate like a coaster, do a three ply layup with face and back of similar veneers oriented in the same direction and either a stable isotropic core material or a veneer core at right angles to the faces. Two ply veneer layups are typically done to reinforce a fragile veneer that is going to be glued to a thicker substrate and will stay flat if held that way until the second pressing, but will almost surely cup with humidity changes if not attached to something more substantial. A lot of fancy marquetry is done with raw veneer so unless you really need a backer you can save yourself considerable labor and experimentation. Contact cement may be ok with phenolic or paper backed veneer if you can't use clamps or a press but I would not recommend it for raw veneer.

Pneumatic presses with heated platens are excellent industrial machines. I don't know what Stephen uses but it may be something like this https://joosusa.com/junior.html. Vacuum presses are more common in small shops due to lower cost, easy storage in the case of bag systems and greater flexibility for curved work. You will find vacuum bag setups even in large millwork shops that do a lot of veneer, though they may also have a pneumatic heated press for production of flat panels. Frame vacuum presses are much more convenient for loading than bags but take up a lot of space if set up permanently. You can increase throughput with a vacuum press by using an electric blanket.

[John TenEyck]

Glad it worked for you. 2 veneer things I would never use when I had a business, paper backing and contact cement. It introduces one more glue line and contact cement doesn't work well if the customer ever shut down the climate control to go on an extended vacation.

It was the best option for putting veneer on Melamine. I haven't found another glue that sticks to Melamine for the long haul. Epoxy sure doesn't, as my friend found out after he used it to glue shop sawn veneer to the sides of some cabinets. It popped off over the first winter. We could easily peel off what hadn't popped off, and we fixed it by putting sticky back veneer on it. 5 years now, still good.

Why would lack of climate control cause contact cement to fail? I made some cabinets for my house when I knew even less than I know now, and glued 1/4" hardwood edging to veneered MDF panels. 40 years later not one of them has come lose, despite not having AC for 30 years and taking many long trips.

I've used quite a bit of paper backed veneer, mostly with Unibond 800, but some with yellow glue. Never has a piece failed. It's no different than using 2 ply veneer


John

[Kevin Jenness]

When I was in employment the shop used a shirtload of paperbacked veneer sheets. We had one project, a 12' maple conference table, that developed hundreds of small surface checks in line with the grain, lifting the finish slightly. We never did get a definitive diagnosis from either the finish or the veneer manufacturer. I felt that it was a problem in the heat activated film adhesive between the veneer and paper. That was the only problem of its kind I am aware of.

Most of our paperback sheets came from Oakwood Veneer Company. Here's what they have to say about contact cement and melamine:

HINTS FOR APPLYING VENEER WITH CONTACT CEMENT

The preferred method for wood veneer application is a vacuum, cold, or hot veneer press with white or yellow glue.
If a press is not available, quality contact cement may be used, but keep in mind that is not the method we recommend.


THE BEST KINDS OF CONTACT CEMENT
Look for contact cement with the highest level of solids and follow the adhesive manufacturer instructions. Keep in mind flammable contact cement often works better than non-flammable.
STIR YOUR ADHESIVE
Stirring your contact cement is an absolute must before each use, just as in painting. The solids and solvents must be mixed thoroughly to form the best bond.
Before applying your contact cement make sure to wipe the backer portion of your veneer sheet down with a tack cloth or microfiber cloth. This will remove any dust or debris that could potentially compromise the glue line and create problems in the glue line itself.
DON’T USE A “J” ROLLER
It's critical to use maximum pressure when smoothing out the veneer. When using contact cement, a pinch roller alone is not enough. When pressing flexible wood veneer to a suitable substrate, the amount of pressure necessary to achieve a good bond is greater than when applying high pressure laminates to a substrate.
A flexible wood scraper should also be used in conjunction with the pinch roller.
Do not use a J-roller, as it does not allow you to apply enough pressure directly onto the veneer. To avoid bubbling when hand pressing your veneer on the boards, be sure to start in the middle of the board and work your way to the outer edges. Use a piece of scrap wood approximately 12" long and 6" wide as a veneer scraper. Lightly sand the 6" edge to take the sharpness away.
The smaller the edge the better as it will produce the greatest pressure. A 1/16" edge will produce 4 times more pressure than a 1/4" edge. Holding the scraper with both hands and, using it like a wooden squeegee, smooth out the veneer from the center outward to the edges.

Do not apply veneer to a two-sided melamine coated board. Do not sand melamine from a two-sided melamine board to apply veneer, as bubbling could result. If the board comes from a manufacturer with one side melamine and the other side raw, you may apply the veneer to the raw side of the board.

[stephen thomas]

Oops - sorry, i missed this.


it may be something like this https://joosusa.com/junior.html.

No, it is not nearly as fancy or large at that one. To my regret. :)
I have several lengths and widths of collapsible discharge hose for some applications including flat or contour work.
And a small 30" x 48" platen capability flat press using Firestroke actuators. Sometimes i use a couple drum heaters (6" wide flat ribbons of silicon rubber embedded with heating elements) and an aluminum caul on one side of the work. I usually use that system for pre-bending parts, or post "un-bending" parts that curved from machining - such as plywood with too many shelf rebates on one side, e.g.

Will try to find pix later.

smt