Gluing up Wenge veneer panels, bleed through issue.

[jon claw]

Hello. I've been working with Wenge veneer lately and I'm having some problems with bleed through. I'm using Unibond 800, because I need the long open time (multiple medium sized panels). I thought that I had the bleed through problem under control by adding India ink to darken up the glue. Not so. I could possibly add more ink to darken it further but I'm not sure how much I could add without deteriorating the integrity of the bond. Any suggestions?

[Tony Joyce]

Hello. I've been working with Wenge veneer lately and I'm having some problems with bleed through. I'm using Unibond 800, because I need the long open time (multiple medium sized panels). I thought that I had the bleed through problem under control by adding India ink to darken up the glue. Not so. I could possibly add more ink to darken it further but I'm not sure how much I could add without deteriorating the integrity of the bond. Any suggestions?

Based on the information you posted, I would say you are using too much glue, use a foam or rubber roller and get an even coat about the thickness of a coat of paint. I've not used Unibond, but have used Better Bond and had bleed through on my fist attempts. Reducing the amount applied and only apply to one surface solved my problems.

Excerpts from Joe Woodworker dot com website:
"The key to applying glue is to put it on evenly. The rule of thumb is that the surface of the substrate should look evenly painted with veneer glue. I've found that, by far, the easiest way is to use a dedicated glue roller."

"A good test to see if you have applied the correct amount of glue is to place a pencil mark on the substrate and apply the glue. If you can barely see the pencil mark on the substrate (through the adhesive), you have the right amount of glue."

"True bleed-through that comes through a clear (non-void) part of a veneer is usually caused by using too much glue and in that case, it really doesn't matter which tone you use because any bleed-through of that nature will not look good."


Disclaimer: My response is based on my experiences only. I am not an expert nor do I claim to be one, so I'm sure someone will disagree with my advise.

[jerry cousins]

i've done lots of veneering with unibond - but not too much wenge - and not large panels - but would imagine that bleed through is pretty severe. i would you suggest you ask your question over at https://www.vacupress.com/forum/forum-view.asp?forumid=3&catlock=1. there are some folks there that have great expertise on veneering - and they're the unibond people.
jerry

[Mike Henderson]

I'm going from memory but I think there's a thickening agent you can add to Unibond to minimize bleed through. Also, as other people have said, minimize the amount of glue.

And I assume you know that you only put glue on the substrate - no glue on the veneer before pressing.

Mike

[Another approach is to use Elmer's Glue-All (white glue). You need to work quickly to get the panel into press, but if you have bleed through, you can wash Elmer's Glue-All off with a wet rag. Also, it dries clear.]

[Harvey Pascoe]

I vacuum bag lots of very porous burls and the way I avoid bleed through is to apply the glue, then SQUEEGE the excess off to the point where I hardly see any glue at all and surface is merely tacky. Then pop the veneer on an apply pressure immediately. Never had any come off and I don't even use a fancy glue. Plus, clamp time is very short.

Some people say to dilute the glue with water to increase open time if necessary.

Most woodworkers have been taught to use an excess of glue. With veneering, this is wrong.

[Richard Wolf]

You need to try the Unibond blocker. Scroll down on the page.
http://vacupress.com/veneerglue.htm

[jon claw]

Thanks all. Wenge is soooo porous that even with the blocker it bleeds through. I did try to minimize the glue at first but found that, even after cleaning with lacquer thinner prior to glue up, the Wenge will resist the glue up. I had some separation. I used to work with Wenge pretty regularly about 4 years ago in a shop, but there we had a heated platen press and maybe the adhesive would would cure before bleed out would occur.(?) I am always checking out Joe Woodworker and Vacupress, as well as purchasing their products often. Lots of good advise and info there. I have way too many panels to use normal woodworking glue. I do veneering on a fairly regular basis and these results aren't so bad that I have to toss the panels away, I just hate not being able to control the results with consistency. And just in case people viewing this post are concrened about the Unibond, Unibond is my favorite adhesive for veneering. Nice and crisp, lots of open time, very predictable, etc. This is just a rare predicament. Thanks again for the responses. Any other comments will be appreciated.

[George Gyulatyan]

I am very new to woodworking and veneering, and soon will be veneering some panels with Wenge, so I am also interested in how bleed through can be controlled? I am wondering if applying some glue size might help?

[Chris Padilla]

Jon,

Since you're familiar with joewoodworker's site, you know that veneersupplies.com recommends/uses the Better Bond veneer glue. I notice that the dark colored glue isn't available. You might drop Joe an email about that but I successfully used it (the dark stuff) with shop-cut walnut veneers (1/16") and it was a pleasure to use. However, you probably don't like the 15 minute open time on it. You might also consider using the Ultra-Cat PPR which as far as I can tell is simply plastic resin glue that DAP sells. That one has a nice open time and dries dark.

[Chris Fournier]

http://www.veneersystems.com/index.php/action/category/id/3/subid/12/

The above link is to a product that is as old as the hills and is designed to alleviate the bleed through problem that you are having. It works very well and is helpful on everything from burls which have open endgrain to coarse pored woods like wenge.

This is the product that I was shown many years ago and I have used it since with perfect results every time.

I would be very wary of advice that recommends going light on the glue when it comes to veneering; while I don't slop it on to excess I always make sure that there is a even film on the substrate. If you think that bleed through sucks, delamination is no better. Again a trial glue up is a fantastic idea when working with a new veneer or process.