Message Thread:
Glue Up Misshap
5/2/13
I'm working on veneering a large table top,60'' x 108''. Plan was to build it as a torsion box, two ply top and bottom. First glue up two plys, then veneer box, all with a vacuum press. Due to the size and number of pieces on the face I first glued up bottom, quartered Mahogany with poplar perpendicular. It went well, too well as I left it in the vacuum all night,and like to never separated it from the 1/2 melamine cauls.I did get it apart with some dime size pieces torn off. Luckily it's the bottom and I've made decent repairs. Never had melamine stick so bad, thought maybe the new formulation of uni-bond was to blame. Next came the top, 12 piece matched Amboyna burl with outer inlay with Sapele border.Intent not to have the sticking issue occur I glued it up, and broke it apart after glue set, about four hours. It was stuck lightly but separated easily. I left it between melamine cauls overnight. This morning I took it out and I have major separation and bond failure, all over the piece. It's hundreds down the drain. I need to figure out how to proceed from here. I waxed the cauls, yet it was trying to stick, but obviously I took it out to soon. I know if I left it in it would have stuck hard. Is the new formulation to blame, I never had it stick so bad with the old. I considering hammer veneering the next try. This job's a loss as of now, can't afford another mistake.
5/2/13 #2: Glue Up Misshap ...
Tim,
Next time try a thin plastic painting tarp which you can get at any hardware store. I have read on different forums that the new uni-bond is very finicky when it comes to temperature! Are you able to save any part of the face?
5/2/13 #3: Glue Up Misshap ...
Yes, I'll definitely use plastic next time. I actually was able to save the burl pieces with little damage by carefully using a 10'' drywall knife and ever so gently prying it apart. Took the better part of the day, but at near $20 per foot it was worth it.I had an extra 4 pieces so I should be good to go. I'm not sure as to whether I should lightly sand the glue side and reglue it, or flip the pieces glue side up and sand it off after pressing. Not sure what kind of bond I can expect if I use the glued side down.
5/2/13 #4: Glue Up Misshap ...
Plastic between the caul and veneer is going to prevent this from happening again, at least the sticking part. You could try switching to Pro Glue UF, I've been using it for years and will never go back to Unibond. Not as temperature sensitive, longer shelf life and lower Formaldehyde content. That and I've had a couple too many problems with Unibond discoloring light colored veneers.
5/3/13 #5: Glue Up Misshap ...
Website: http://www.acornwoodworks.com
Tim - That is one sad tale, but sounds recoverable. I also suggest the plastic sheeting - cheap, easy and fool-proof. I used a lot of 'shower liner' for cauls - white masonite sheet stock that usually resists glue, but after a few uses starts sticking. I used to wax it, then just inserted the plastic sheet.
Bob....tell me more about the "Pro glue UF". Google doesn't get me much. Who makes it, where can I get it.
I have used Unibond for years and just recently had a few places on a large table that did not bond well - first time for that problem. Shop and materials all heated beyond specs, etc, but still a problem - not happy. Previously, I had problems with Uni-bond and discoloring Maple veneers.
5/3/13 #6: Glue Up Misshap ...
Website: http://www.veneersystems.com
We don't sell Pro Glue but sell a product which is similar and we sell a lot of it. We also sell Unibond 800 and the formula was changed a year ago. They removed 90% of the urea formaldehyde. Both glues can be tinted using titanium dioxide to lighten the glue and any water soluble dye to darken them.
Veneer Systems products
5/3/13 #7: Glue Up Misshap ...
Thanks for all the input. Any thoughts as to which side of the recovered veneer I should re-glue ? I'm doing a small test panel doing it both ways, but would like to hear more. I like the idea of using a shower curtain, good call, easy to lay out I imagine. I may switch glue as John suggests, but I'm a little nervous about introducing that much water on such a large piece. Then again this new and improved formula has aged me ten years! Green my #?!! :)
5/3/13 #8: Glue Up Misshap ...
Website: http://www.acornwoodworks.com
I also do not like to add any water to my layups, so that is why I always used the Uni-Bond 800. I assume it has some water, but ??? I'm curious as to any feedback on that part of the discussion.
Also, I use 'shower liner' - a 1/8" x 4 x 8 masonite board that is painted with a heavy white paint on one side for the cauls. About 5.00 a sheet at the Home Center. Then I use just plain plastic sold as painter's tarps or whatever - heavy enough gauge to re-use.
5/3/13 #9: Glue Up Misshap ...
Tim
How are your seams held together? If you used veneer tape I would not put them in the glue line. Is the unibond hard on the glue panel if so go with that side? What glue are you using for your test sample? Tom
5/3/13 #10: Glue Up Misshap ...
Tom,
I used uni-bond on the new sample, one glue side up, one down. I'll check bond Monday, and probably blow a coat of finish to see if there's a difference. I used veneer tape, so I'll scrape it off if I go glue side up on the top.
5/5/13 #11: Glue Up Misshap ...
David, I get my Pro Glue from the manufacturer here is CA, Vac-U-Clamp - see link below.
They also have a few other glue options in case UF isn't your first choice. I stopped using Unibond years ago after a few bad glueups. So far no problems with ProGlue, it is water based though. Comes as a dry powder in either tan or white and is mixed with water. The two colors can be blended for different shades of tan/brown. The powder has a very long shelf life compared to Unibond.
Vac-U-Clamp
5/6/13 #12: Glue Up Misshap ...
Website: http://www.acornwoodworks.com
Bob - Now I see I have used Pro-Glue before. It is one that we use for 'butcher block' glue ups, but it needs 70 degrees or better. I'd love to get that temperature down to 60 or warmer, but I have seen failures at just under 70.
Also, do you have any problems with thin veneers in sketch faces expanding or moving with the 'water' that is inherent in the mix?
5/6/13 #13: Glue Up Misshap ...
Website: http://www.veneersystems.com
Both Unibond 800 and plastic resin glues contain water. The plastic resin glues are a pre catalyzed resin powder which when you mix in the water restarts the chemical reaction bond. Unibond 800 is a liquid resin with water in it and you add the powdered catalyst to the resin to restart the chemical reaction bond. Both of these types of UF need to be 70F or warmer to cure properly. There should be no issues with the water as this a chemical reaction bond not an evaporative bond like PVA's. PVA's are thermo plastic and do not dry hard. In Germany the UF glues are called Hart leim which translates to hard glue.
5/6/13 #15: Glue Up Misshap ...
John, doesn’t unibond have alcohol in it that gives it that nice smell?
Tim how did your test pieces turn out?
5/6/13 #16: Glue Up Misshap ...
Tom,
Both samples turned out fine, no bond issues with either one. I sanded and put a clear coat on and you cannot tell which is which, so it looks like I'll be gluing it glue side down after a light sanding.. That's what Darryl Keil over at Vucupress.com suggested as well.
5/6/13 #17: Glue Up Misshap ...
Tim,
So does it come down to the time it stays in the press more than temp? Or is it both? Also what did you use to cut your seams? Tom
5/6/13 #18: Glue Up Misshap ...
Website: http://www.veneersystems.com
Yes it is 21% furfuryl alcohol. The Physical and Chemical description from the MSDS states "Off white, water solution of urea formaldehyd resin and furfuryl alcohol.
Odor: formaldehyde, furfuryl alcohol."
5/6/13 #19: Glue Up Misshap ...
Tom,
Temp was 75F so it's just a matter of leaving it in longer. I should have intuitively known that two ply would want to move more than a regular layup. I use veneer tape to seam.
5/23/13 #20: Glue Up Misshap ...
Website: http://www.hawthornecrafts.com
Non stick baking paper - comes in rolls and nothing sticks to it.
Ian
5/24/13 #21: Glue Up Misshap ...
Get yourself a couple of pieces of Mylar. It's a little expensive, but nothing sticks to it, I mean nothing and you'll get years of use from it if you take care of it.
6/5/13 #22: Glue Up Misshap ...
Thought I'd give an update on the top. Just finished rubbing it out, ready to set on the base.
View higher quality, full size image (600 X 450)
6/5/13 #23: Glue Up Misshap ...
Website: http://www.acornwoodworks.com
Looks like you were able to make it all work. Nice work!
6/5/13 #24: Glue Up Misshap ...
Nice job, table looks great.
6/5/13 #25: Glue Up Misshap ...
Tim,
Looks great thanks for sharing. Tom
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