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Unibond 800 VS West systems epoxy for veneering.11/23
I used some Unibond 800 for the first time today. I didn't really care for it. I mixed as per instructions and had trouble getting all the acid crystals to dissolve. I am thinking of using west systems epoxy next time what is your opinion?
Unibond is one of the best for veneering. I wouldn't want to veneer with epoxy on a regular basis, though it does have its uses in some situations.
Next time try by mixing the unibond at about a 1:1 ratio until all crystals dissolve. Then add liquid until desired ratio. This should do it (though I have found the light powder to be the most difficult...)
I will never use Unibond again for veneerwork, ever. I know it has a great reputation but for me it has only caused problems. If you don't get the acid crystals to dissolve they will eat away at the veneer from the back side until the veneer face is covered with a bunch of greyish brown dots. Not fixable, not concealable. Spoke with the manufacturer and he mentioned using a power mixer and mixing it twice with a delay of a few minutes in between. Funny, the instructions on the bottle just say mix well. He knows about this issue (and has known for years now) and has done nothing to update his instructions or website. He mentioned that even if you can't see the crystals they may not be fully dissolved, thus the twice mixed system.
Have had no problems with ProGlue which is a lower formaldehyde version of a urea glue. Dries hard and has several different colors. Just my two cents.
Epoxy works great with sawn veneer as you don't get any bleed though and have a hard glue line. The glue joints between pieces may be dark though unless you pre-glue the seams with yellow glue and press the entire face at once.
Jeff, Can you comment on whether the Pro-Glue mentioned is a suitable alternate to Unibond?
Chris, as far as I can tell, the "ProGlue" is a private label of powdered UF resin. It would not have lower formaldehyde emissions than the Unibond 800 but it would have less furfuryl alcohol in it. The furfuryl extends shelf life and adds to the wetability of the resin. Either product would be a better choice than an epoxy resin. I believe that the manufacturer of Unibond is about to introduce a new version that will be a thermosetting resin with no formaldehyde emissions. If so, this would be the ideal choice for this kind of application. As for the "acid crystals" in the Unibond catalyst it sounds like the catalyst might have been exposed to moisture. Catalysts of this type are very hygroscopic picking up moisture very easily. This usually translates to small "hard" pieces that don't dissolve easily and can telegraph. It's important to keep any of the powders sealed in a cool, dry place. The same effect can easily happen with the "ProGlue" as well.
Jeff, Are there any examples of this kind of thermosetting resin on the market now?
At the moment there aren't really any commercially available products that could be used on a small scale. Most of what is being used is melamine/urea which requires a hot press. As I understand it, the upcoming product from Unibond will be something quite revolutionary in the market.
Jeff, I have an application where I could use heat. Can you suggest a direction to research the melamine/ureas, or a manufacturer/product name/#? I can't use drum quantities though yet. Thanks,
I recently became aware of this thread so I'm jumping in rather late but hopefully what I say will be of use to others.
In response to the first poster's concern with the acid crystals, it is not an issue with a 1/16" veneer. This veneer is too thick for the staining that can happen to come through. Most maple veneer is now cut in the 1/40" range where the chemical staining can occur.
Let me back up and explain more about Unibond 800's characteristics in this regard. First, the active ingredient in the catalyst, which is usually ammonium chloride, does not "eat" at the veneer but reacts with some of the resins in certain veneers, only some of the time, causing a chemical staining if the "crystals" are not fully dissolved. For the most part its restricted to maple and english sycamore. Ninety nine percent off all veneers are not effected. The odd thing is that it only happens every once in a while. Someone can veneer with Unibond 800 a dozen times on maple with no reaction and then on the 13th time the staining occurs. Obviously the poster who was angry about his results with Unibond 800 was unfortunately having that "13th time" reaction. We have countless customers who use our glue on maple and never get this. I assume its got something to do with the soil the tree grew in, more or less acidic. Maple of course is notorious for staining issues like sticker stain, and even a pre-catalyzed PVA glue can sometimes stain maple pink, go figure. Every glue has it strengths and weaknesses. Thats why I never rely on just one glue for every situation.
On another note I understand there is a common perceptions that manufactures often choose to ignore and even attempt to cover up short comings or problems with their products so they can continue selling them without consequences, like a manufactures "watergate", so to speak. I find this totally unacceptable as a manufacturer and for quite a while now the instruction sheet that comes with every gallon of Unibond 800 speaks directly to this issue.
Lastly, in response to Jeff's comment about a new Unibond glue. I suppose we are close enough to releasing, what we will call "Unibond Green", that I'll say a few words about it. Unibond Green which we are very exited about, is a hybrid thermosetting melamine resin glue that will fully cure at room temperature. The really exciting thing about this two part catalytic glue is that it achieves a rigid bond without formaldehyde emission. There is nothing like it on the market and it exceeds the new California CARB phase 2 standards. We expect to have it availible in the next few months.
Daryl, I'm a customer of Unibond 800 and very much look forward to evaluating the new product. If you need a test from a real world product, email me an I'll describe the application where I would try it.
It's nice to hear that your instructions have been updated as they should have been long long ago when you first discovered or were informed about this issue.
Bob, I'm sorry to hear you have had so much difficulty getting success with Unibond. This is quite uncommon as we would not be selling the quantity of Unibond 800 that we do if everyone had the experience you have. If you were still using this glue I would give you some suggestions on how to avoid these problems but it sounds like you're happy with what you are using now. Wish you the best.
I know this thread is probably pretty old but I just wanted to respond to it to say I have been using Unibond 800 for years and have never encountered any of the problems mentioned above. I use it exclusively for all my veneer and curved work. I think making sure it is mixed thoroughly is the key. Just my two cents though. Cheers