Glue Problem

[Harvey Pascoe]

I laminate 1/8" veneers onto 1/8" birch plywood using a vacuum bag with with water based glues and I'm tired of fighting with the warpage problem, I can't use epoxy because I'm alergic to it. Veneering the other side is no solution.

Can anyone recommend a non water base glue for laminating? How about that gorilla glue which is polyurethane or something like that?

[Philip Rodriquez]

premixed unibond. ;)

[Frank Drew]

Harvey,

Philip's suggestion is one you could try immediately.

You've tried veneering both sides of you panel with equal thickness veneers and still get warping?

How about using thinner face veneers and/or thicker core stock?

[Peter Quinn]

From the Joe Wood worker site: "Unibond 800 is a two part urea resin glue that offers excellent adhesion and stability. The real benefit is that you are not introducing water to the veneer and substrate which can cause seams to separate, thin substrates to warp, and some veneers to develop moldy areas. Cleanup can be difficult and a gallon of this adhesive is a bit expensive, but for that ultra-special veneer, this might be your best option. This adhesive is also good for adhering oily veneers such as rosewood. Unibond requires 4 to 6 hours in the vacuum press to bond."


So there you have it, a non water based glue that resists warping. But realistically, gluing an 1/8" veneer on only one side of an 1/8" substrate, and expecting that to stay flat seems to me unreasonable. I've seen 1/8" of bubinga glued to only one side of a 5/8" baltic birch substrate with epoxy take it for a ride the first time the weather changed.

[Harvey Pascoe]

My products are decorative boxes no bigger than 12" for which the tops are mosaics of veneers. The top panel is glued into a rabbetted frame of only 1/2" thickness, photo below. I am presently using Tightbond and spreading it very thin but still get minor warpage. The advantage of this is I pull it out of the bag in only 30 minutes. Never had a glue failure. Sometimes it will crown, sometimes dish, and others it ends up flat . . . I never know.

Unfortunately, 4-6 hours in the vacuum bag would be way too long for me as my system is going non stop all day.



http://www.pascoewoodart.com/images/mens_valet_box_VM5-1.JPG
(http://www.pascoewoodart.com/images/mens_valet_box_VM5-1.JPG)

[Sam Layton]

I know nothing about veneering. That said, what about placing your 1/8 veneer and 1/8 ply assembly, on 3/4" ply, and place everything in the bag. Would the 3/4" ply keep the assembly flat while the glue sets?

Sam

[Howard Acheson]

Your constructon is creating the problem. Merely substituting a waterless adhesive will not be the solution. Gluing solid wood onto a composition material substrate creates the problem.

The solid wood will want to expand/contract with changes in relative humidity. The composition material is not affected by the humidity change. As you have your hardwood veneer on only one side of the substrate, the substrate will warp due to the expansion/contraction of the veneer. The only solution is to apply the same thickness of veneer to both sides of the substrate.

Let me ask you, have you been making these it for a period of time? The reason I am asking is that the design seems to have your veneer patterns with the direction of the grain going in many different directions. If so, the individual pieces will expand/contract at differing rates and amounts. This can lead to the seams opening up or localized warping as the relative humidity changes.

[Harvey Pascoe]

With pieces of wood that small any expansion/contraction from atmosphere is negligible. Plus, the wood is sealed with either lacquer or varnish. I've been making boxes like that for 8 years without a single failure. Even the joints under a gloss finish don't show. Keep in mind expansion is relative to size of wood, and these are small.

[Greg Wease]

Although I don't like the stuff (messy, outgasses, stains fingers, short shelf life, ...) I have seen gorilla glue used successfully on laminations. This might be a lower cost option to Unibond 800 which I agree with the others is your best bet.

[ian maybury]

This is fairly speculative, but it strikes me Harvey that a heat curing adhesive might offer some potential.

The big advantage is that a single part, water free and high performance normally two part adhesive might become an option. The heat activates the cure by triggering a hardener that's already mixed in. So the problems of handling two pack adhesives disappear.

For anybody else there are lots of heat curing epoxies around. e.g. http://www.permabond.com/en/en-epoxy-single.htm

Permabond were a part of Loctite, and their products were more engineering than woodworking focused when i worked for Loctite.

There are probably other heat curing adhesive types already used in woodworking that a search/talk with some of the big suppliers might bring up for you Harvey.

The Permabond epoxies seem to need to be brought up to 120 - 150deg C to get a 20 - 40 min cure, but other adhesives may get by with less heat. I don't know how ply/other wood and veneer might handle those sorts of temperatures, but clamping between platens might avoid issues.

I don't know if its been done, or even if its an option - but maybe you could even zap an adhesive joint in a microwave which might avoid delays while waiting for the heat from an oven to penetrate - your small boxes open up options like this.

The advantage of somebody like Loctite/Permatex/Henkel is that they usually offer very high levels of tech support, but the products are very expensive compared to the more typical commodity type wood glues. If you can ID an adhesive name/number a technical data sheet or TDS (Google it, many come up) should set out most of the basics about it.

Anyway - just a thought.

Ian

[Chris Padilla]

I laminate 1/8" veneers onto 1/8" birch plywood using a vacuum bag with with water based glues and I'm tired of fighting with the warpage problem, I can't use epoxy because I'm alergic to it. Veneering the other side is no solution.

Can anyone recommend a non water base glue for laminating? How about that gorilla glue which is polyurethane or something like that?

So I assume you have tried veneering the other side with little to no success in controlling the warping?

I've veneered 1/16" shop cut walnut veneer to one side of 1 1/4" thick MDF (really, two pieces of 5/8" thick MDF previously laminated together) and it managed to pull that into a decent arc by the next day. That transformed me into a big believer in veneering in a balanced fashion.

Have you tried different substrates or even different vendors of your chosen substrate? Ever consider making your own substrate? :)

Your "veneers" are quite thick at 1/8". So thick I put "veneers" into quotes because I believe they will still exert a lot of force when they move despite their size. The thinner the wood, the less force it will exert when it tries to move. Try going for thinner veneers and see if that helps.

You also want a glue that dries very hard and rigid. You don't mention the glue you are using but if it is PVAs (good old yellow and white glue), those do not dry hard...they tend to remain flexible...not good for veneers usually. I like the Better Bonds glue over at www.veneersupplies.com (http://www.veneersupplies.com). I used that for all my veneering on my Tansu (http://www.sawmillcreek.org/showthread.php?t=92396).

I agree with Howard: the glue isn't likely to be your problem but by all means try the Unibond and see for yourself. You could also try the poly but it is about as messy as the Unibond. It does have formaldehyde (sp?) in it...not sure if that would bother you. You say you are allergic to epoxy but I'm wondering what in epoxy it is that gets you?