Veneer glue up failure

tvrgeek

tvrgeek
User
First few pieces worked OK. Last one was a total failure in it did not bond. The glue was just a little thinner than before. Was that the cause? Doing another piece now thicker. Vacuum was only on for about 6 hours as I did not think I trust the cheap pump to run unattended all night.

Using the DAP powered resin glue. Not the brand suggested buy I could get a reasonable quantity for the project.
 

Phil S

Board of Directors, President
Phil Soper
Staff member
Corporate Member
I have some epoxy left overs you can use up Plus I have a vacuum pump you can use, designed for continual duty. I am in NE Raleigh
 

tvrgeek

tvrgeek
User
For now, working with what I have. I would not be surprised if I wind up starting over. I probably should get a supply of West anyway. I made the mistake of not moving a lot of my chemicals when I came down here. Now I find that was a big mistake. I should be able to get a good 10 hours of clamp time today. Don;t want to blame the tools and materials when it is probably operator error!

The test piece I did with big-box 5 minute had bleed through. It would be fine making the cold form, but not for the veneer. Of course, if I could afford veneer that was not almost transparent, it would be easier. If I start again, I will investigate that route. I have just enough off the roll I can redo the piece that did not stick. More than that, back to the Hardwood Store for some decent ply.
 

Bernhard

Bernhard
User
Not sure what you are veneering, so this may not be applicable...
For regular raw veneer I use about 45 - 60 min clamp (=vacuum) time. For wood veneers I find it much easier to use pre-mixed glue ; I use Joe Woodworkers Better Bond (Veneer Glues & Adhesives: A "Sticky" Category) and I never had a failure.
Bleeding may be caused by thin and slow setting glue in addition to porous veneer. Also too long of a clamping time may worsen bleeding: Vacuum pressing works well for pressure and initial set, but is very inefficient to remove the additional water. The generally longer open time of resin glue makes it a bit worse in my hands.
Lastly -at least for wood- I'd stay away from epoxy; imho it will make bleeding worse, finishing can be a nightmare, it is expensive and clean-up is a mess. The fumes also don't help with the longevity of the pump.

Bernhard
 

tvrgeek

tvrgeek
User
The DAP feno-resin glue takes about 6 hours to get firm enough to release the clamps for veneer. To get really hard, overnight. My mistake seems to have been mixing it too thin Did a much thicker batch for the next one and it worked fine.

Of course, this super thin veneer is porous . ( Walnut over plywood. ) I would think continuous vacuum would greatly assist with removing moisture. Lower pressure, greater evaporation.

All those magic veneer glues in the link are for "normal" environments. My use is inside a car, so temps from sub zero to 135 or higher and humidity from zip to 100%. A hostile environment that can make almost anything that is not a chemical reaction let go. 3M supper 99 spray? Yea, it gives up too.
 

danmart77

Dan
Corporate Member
The DAP feno-resin glue takes about 6 hours to get firm enough to release the clamps for veneer. To get really hard, overnight. My mistake seems to have been mixing it too thin Did a much thicker batch for the next one and it worked fine.

Of course, this super thin veneer is porous . ( Walnut over plywood. ) I would think continuous vacuum would greatly assist with removing moisture. Lower pressure, greater evaporation.

All those magic veneer glues in the link are for "normal" environments. My use is inside a car, so temps from sub zero to 135 or higher and humidity from zip to 100%. A hostile environment that can make almost anything that is not a chemical reaction let go. 3M supper 99 spray? Yea, it gives up too.
Its funny thinking about what you are considering when you choose glue. I have a 1950 MGTD and I had an older Morgan Plus 4 with wooden dash features. By the way they were both fancy burl veneers applied with hide glue. That's all they had back then.
 

tvrgeek

tvrgeek
User
Thinking back. I think my +4 had a solid wood dash. Factory, they were not burl. Would have been hard to do the radius for the glove box in veneer. OK, Bentely perfected doing that somehow. Not sure how, but I think they use a steam press or something.

Anyway, read an analysis of all the various glues, how they hold up with stress, temperature and moisture. I can see a big advantage to hide for furniture. It does not creep, so that is good, but it's resistance to moisture is not that great and it's bond strength is not that great. Another project is a new center channel speaker cabinet. Might give hide a try there. It will be a single curve, not like all my previous cabinets. Last couple came out better. Maybe too thick last time as it left small ripples, but within sanding thickness. One piece in the bag now, and then the big instrument cluster.

I see new liquid hide glues, but reading, it sounds like the behave more like PVA.

They had newer glues as the floors and bulkhead were plywood in the +4. I assume Formaldehyde based. Even epoxy was invented in the '30s. Of course other glues were used for plywood as it goes back to Egypt BC. Hide glue fails @ 140, so marginal inside a closed car. I figure is is that harsh as some of the factory glue had failed.
 

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