So I’ve had a problem a couple of times now with glueing on veneers and I’m not sure what’s happening. These were all done before I got my vacuum press.
The problem arises when it’s time to start the finish. After raising the grain and sanding I’ll then put whatever stain I’m using (black mostly) first to help bring out the figure. All of my stain is water-based and I’ll end up with spots where the veneer has bubbled up, basically swelling from the liquid it soaked up I’m assuming. But it bubbles up and is clearly not glued to the body.
My question is, is that due to bad clamping or bad glue spreading? And should glue be spread on both the body and the veneer or is one surface enough?
Hi Rathaus,
I remembered your post about problems with veneering while I was watching this video https://m.youtube.com/watch?v=5lFoUAKkYWU
The guy talks extensively about different glue types and their properties in regard to veneer applications. Thought it might be of use to you.
All the Best, Brian 👍😃🎸
@brie thanks dude, much appreciated. However, I’ve decided to not use veneers anymore after I use up the remaining veneer (6 I think) or sell them. Instead I’m moving to drop tops and carve tops. Much better results visually plus adds a tad more creative options. Around the edge though I run a 1/4” round over bit and leave a raw edge with no color just clear. Has quite a stunning effect and draws a lot of attention.
@brie First off, thank you for finding and sharing this. Great info. I actually bought a 1/2 gallon of Unibond 800 w/hardener AND a 1.5 lb pack of Unibond Blocker. Figured since I still have several veneers I might as well get some. It’s actually arriving in the mail today! YAY!!! Not that I’m gonna use it today mind you but soon(ish maybe?). Shit I dunno but I’ll use it for sure.
Hi Rathius and happy new year to you.
You really shouldn't be seeing this kind of failure if the veneers are bonded properly in the first place and it suggests to me that they haven't been pressed firmly to begin with. You don't say whether the veneers were being pressed onto flat or profiled bodies, or what species you were using (Santos Rosewood can be a particular problem with PVA for example), but in either case I think you will find that using your vacuum press will give you entirely different results. I can offer the following advice:
1. You don't need to apply the adhesive to both surfaces, just to the body, and you don't need to over do it. The adhesive only has to fill the pores in the material on either side of the glue line and if you use too much it will simply make a mess and take much longer to dry out.
2. I have used a D3 PVA for the vast majority of all the veneering I have undertaken in my life and it works perfectly well for the vast majority of veneers and substrates. Using a UF resin type system with a grain blocker powder such as the Unibond 800, will really help to reduce squeeze through. I would only ever use UF resin for laminating acoustic guitar backs and sides as this adhesive cures much harder than PVA and therefore doesn't present the risk of deadening the acoustic properties of the material.
3. When bonding veneers in a vacuum press always have another layer of thin, hard material (a caul) on top of the veneer as this prevents any localised swelling that may occur, especially when using water based adhesives with highly figured veneers. The caul can be a layer of thin birch plywood (0.8mm-1.5mm) with some clear parcel tape stuck on or just use a layer of polythene in between.
4. Don't apply lacquer to a veneer that has been bonded with a water based adhesive for at least three of four days after pressing, as it takes this long for the moisture levels to return to normal.
5. You will find that UF resins have a pretty short shelf life, usually only three to four months, so after this period you will find that your Unibond 800 is starting to thicken considerably. My advice would be that if you can still spread it relatively comfortably then it is perfectly ok to use beyond its stated 'use by' date and you will be able to tell when it has really 'gone'.
Have fun and don't give up on veneers as they offer huge variety of creative options and are an extremely economical an environmentally friendly way of using rare and precious materials.
Kind regards
Darren
@darrenking up until I got my vac press it was only flat guitars. I’ve done 2 with my vac press since I got it and I still had some bubbling in a couple of places with both. Was using Titebond III which is supposed to be waterproof. One was flat the other has an arm carve.
Things got a little crazy around here for a few months and I haven’t tried doing another veneer since but did purchase the Unibond 800 and blocker. None of that has been opened yet so hope it doesn’t go bad before I use it.