Darryl Keil Last Activity 2025-02-12 2:48 PM
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Bruce E

 
Subject : Bleed through
Posted : 2005-11-06 7:08 PM
Post #32538
I'm looking for a good solution to glue bleed through. Has anyone tried coating the glue side of the veneer with shellac. It seems like this would add a good barrier to the glue being drawn through the pores but still allow a good bond.


 
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Donald A. Barnhorst

Posts: 5

Joined: 2005-08-01
Location: Ponte Vedra Beach, FL

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Subject : RE: Bleed through
Posted : 2005-11-06 9:28 PM
Post #32539 - In reply to #32538
I unfortunately do not have a solution, but I share your problem. Especially with porous veneers, such as walnut burl, Unibond bleed through has been difficult for me to handle. Regardless of my thorough scraping and sanding, some areas of bleed through show residual shiny areas after the finish has been applied. I have concluded that, since the Unibond has penetrated all the way through from the glue side, some residual is present in all the microscopic layers out to the finished surface. I'm sure Darryl has a good solution for the problem; so, I await his wisdom.


 
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Anton Gerner

Posts: 45

Joined: 2003-09-04
Location: Melbourne, Australia

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Subject : RE: Bleed through
Posted : 2005-11-07 3:44 AM
Post #32540 - In reply to #32539
Try applying less glue.
If you can still see the glue after sanding and scraping it normally means you have applied too much glue.
I vacuum press veneer almost every day in my business and although we have glue bleed through it generally cleans off the veneer surface very well when we apply the correct amount (which was determined by trial and error).


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : Bleed Through
Posted : 2005-11-07 9:56 AM
Post #32542 - In reply to #32540
Just a brief note - I try to roll out just enough Unibond so that, if I drag my finger through the glue, a small ridge is formed on each side of the drag. I don't recall having shiny spots under the finish.

After sanding/scraping, lightly wet the surface of the veneer with distilled water or naptha, and while the surface is wet look for any shiny spots. Neither of these liquids should affect either the veneer or the eventual finish if allowed to dry completely. Seems like bleed through usually is removed by the initial 80 grit sanding, and any remnant disappears during 150 and 220 grit sanding. Haven't vacuum pressed walnut burl, but I have worked with some burl veneer that was still not flat after the normal regime of 80, 150 and 220 sanding. Is it possible that this veneer was still not completely flat, and that some of the bleed through was in such low areas? If possible, go over the finished burl with a hard sanding block and fine sandpaper, to see if the shiny spots are lower.

Hope this helps.


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: Bleed through
Posted : 2005-11-07 9:35 PM
Post #32545 - In reply to #32538
Bruce,

Ah yes, the curse of bleed through. We all deal with it.

I always say that bleed through is a sign that you can be sure that enough glue was applied. On any open grain wood I tend to get nervous when I see no bleed through. Better to have some bleed through, even just a little, than none. With that said a lot of bleed through is a major pain and I like to see just a little spotting here and there.

As far as the shellac idea I have never tried it so I cant say absolutely how that would work. My concern would be that the shellac might penetrate deep enough to prevent the glue from bonding properly. Don't really know since I haven't attempted it.

I don't know if you are using Unibond 800 but if you are consider getting the Unibond Blocker which is meant to eliminate or minimize bleed through. This should help your problem. The other solution is backing off the amount of glue you apply until you get just a little spotting as I said earlier.

Sincerely
Darryl Keil


 
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Brian Gray

Posts: 339

Joined: 2004-01-21
Location: Sandusky, OH

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Subject : RE: Bleed through
Posted : 2005-11-07 9:45 PM
Post #32547 - In reply to #32545
Lately, I've been using a spreader that I bought over at JoeWoodworker.com

http://www.joewoodworker.com/catalog/product_info.php?products_id=56

It's a simple and very cheap notched spreader with three different sized teeth on three sides. I use the middle sized teeth, and have been getting great consistent results ever since.

The finger method that Don mentioned above is what I use to do and never really had any problems...I just thought I'd try Joe's little spreader, and it really works well.




 
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DKA

 
Subject : RE: Bleed through
Posted : 2005-11-09 1:25 PM
Post #32555 - In reply to #32538
I almost always make a 2 ply before I apply my veneer to a substrate. I like being able to sand a little and look for trouble spots before I apply to the structural piece.
On my 2 ply's I use a PVA veneer from Vacu Systems that has a high solids content and is made especially to minimize bleed through.
Then, when I am applying the 2 ply to the substrate, I use Unibond and get no bleed through to the surface.
I don't think there is a problem using 2 different adhesives on the same peice, at least I hope not. I get the benefits of both ( minimized bleed through from PVA and rigid strength from Unibond) I haven't experienced any problems yet. It's an extra step but I think it is worth it.
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