Darryl Keil Last Activity 2025-09-09 11:09 AM
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Loren Larson

Posts: 6

Joined: 2008-01-23
Location: Aurora, CO

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Subject : Delamination at seams and concave form, urea glue
Posted : 2008-01-23 12:12 PM
Post #34313
I am having serious problems with door and panels. I am Veneering Adiroba (Mahogony like) to flat panels and also concave panels (using a convex male form.)25"x96"

The veneer(vertically laid) is easily peeling up from the first layer of horizontal Vaneer (Aniroba) occuring most along the seams and edges but also in spots all over the surface. It is worse on the concave surface.The first layer over MDF did well on flat surface but I had peeling on concave surface.

Andiroba veneer is from Certainly Wood.
Glue was rolled on - Pro-Glue Veneer Bond Dry resin purchased from Vac-u-Clamp in the last 30 days kept the cover on.
Located near Denver.
Room Temp was at least 65 and used an electric blanket to raise surface temp.

Any ideas would be greatly appreciated


 
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Don Stephan

Posts: 825

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

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-23 8:38 PM
Post #34316 - In reply to #34313
Loren:
Since this is your first post, we don't know your background so please bear with some background questions.
Have you enjoyed success with this glue previously, or is it the first time you've tried it? Same with the andiroba . . . Same with the MDF . . .

The veneer was pressed using a vacuum bag? If so, did you check the vacuum level at any time during the pressing? Does this glue usually bleed through for you, and if so did it bleed through this time?

Did the excess glue cure rigid? If so, the glue itself can be ruled out.

Found a source on the wood, and didn't mention any inherent oil issues like teak; in fact, said it glues well.

I'm having a bit of difficulty understanding exactly the materials used. The flat panels are MDF? Single layer of andiroba on each side? If double , crossbanded layer, did you press everything at once, or first press one layer to each side and later the second layer? If the latter, were the panels stood on edge and allowed to cure, after removal from the press, for at least 12 hours?

Regarding the curved panels, could you describe a bit more how they were made? Material, adhesive, # layers, pressed first or simultaneously with veneer? If cross banded, same questions at with the flat panels.

Hopefully with some more info someone here can help identify the problem.

Don


 
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Loren Larson

Posts: 6

Joined: 2008-01-23
Location: Aurora, CO

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-23 8:55 PM
Post #34317 - In reply to #34316
Don, Thanks for your reply. My assistant actually wrote the original post, so sorry about the missing info, although I'm not sure I would have done any better!
My background is that I am a professional woodworker, but had taken some time away from every day woodworking. I am happy to be able to work full time in the shop again, but this project is kicking my butt! I was part of a co-op shop in Denver until the early '90's, when I left the business. We had a shared vacuum bag system at that time, but I must admit that I did not do very much veneer work myself. A couple of fairly extreme projects, but not a great deal of volume. I only used PVA glue at that time, but with the extent of veneer work on this project I decided to use the urea resin - mainly because I knew that PVA was not the best choice, and I thought the creep factor would be better avoided.
Anyway, the curved panels are made up of 6 layers of 1/8" 3-ply meranti, which we glued separately from the andiroba. We then glued one face at a time (I'm short tempered) for a cross band. Much of this cross band delaminated on the concave side, and we gave up and used Bondo for the repairs. I have used Bondo a lot in the past without any problems, and it doesn't seem to be part of the adhesion problem now.
We have not tried to push time on anything except possibly the time in the bag - with the heating blanket, we have been taking the pieces out after about 3 hours. The glue is drying rigid - not rubbery or gummy. We have not done subsequent gluing before at least a 12 hour additional open air cure.
The flat panels are MDF, standard-not Medex or anything special. No crossbanding on the flat panels - only on the curved ones due to the grain direction of the plywood substrate being parallel to the face grain. I have since read in a couple of posts on this site that I could have skipped the cross band in this scenario. I wish I had!
This is the first time I have used this glue, and it does seem to work better on the panels where we have extensive bleed...I do think the one thing about the concave problem is a somewhat dry mix on the glue and possibly too thin a coating.
A long post, but hopefully covers all the questions...
Thanks.


 
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Don Stephan

Posts: 825

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

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-24 7:50 PM
Post #34322 - In reply to #34317
Three hours in the bag seems very quick, at least for the urea formaldehyde glues I've used. A trick that Darryl Keil taught is to pour a couple tablespoons of excess glue in a small zip-lock bag and place on top of the vacuum bag (and under the heating blanket if one is used). When the glue in the zip-lock bag is at least rubbery then the adhesive should be sufficiently cured to remove the job from the vacuum bag.

I'm not familiar with the veneer you are using, but if the flat panels seem okay, look at the amount of bleed through of the adhesive to the surface of the veneer, and compare it with the amount of bleedthrough on the curved pressing. There are a few types of veneer that have such tight grain they allow little bleedthrough, but most show splotches of bleed through over the entire surface - one indication of enough adhesive on the substrate. I usually roll out the adhesive in both directions a number of times to try to get an even coat, sufficiently thick so that if I drag a finger on the surface of the substrate a small ridge of adhesive appears on each side of the drag.

If this doesn't help, keep posting and hopefully someone on the forum will deduce the problem.

You're also welcome to download a collection of veneering notes, most of which was copied from discussions on this forum. The notes are available in MS Word and .pdf format at www.stephanwoodworking.com/downloads


 
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Darryl Keil

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Joined: 2003-05-22
Location: Maine

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-25 8:06 PM
Post #34324 - In reply to #34317
Loren,

A question, is the veneer on the convex side of the door bonded fine? As far as the seams go is the trouble only on the concave side of the door as well, or all seams, convex and flat?

Darryl Keil


 
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Loren Larson

Posts: 6

Joined: 2008-01-23
Location: Aurora, CO

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-29 12:37 PM
Post #34343 - In reply to #34324
Darryl,
The delamination on the curved panels is only on the concave side. I should note that we have different species on each face, typically - wenge on the convex and andiroba on the concave, and the wenge is bonded fine, except where we had some seam overlap occur after the peices were in the bag. We are having some problems on the flats, mostly with the andiroba. I think we may have been too light on the glue with the andiroba. It must just soak up too much moisture. On the flat panels, we have had problems at seams and mid, but only with the andiroba.


 
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Darryl Keil

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Joined: 2003-05-22
Location: Maine

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-29 9:16 PM
Post #34344 - In reply to #34343
Loren,

The additional information is very helpful. I was originally thinking that maybe you were not getting a good mate between concave side of your panel and the form. This can easily happen when the panel is made first, then put back on the form to veneer it. If the panel is not placed exactly in the same spot it was pressed in you can get imperfect mating which will cause spotty bonding of the veneer on this side of your panel.

In reading you post it sounds more like your having problems with the andiroba veneer, not so much the concave side of the panel. Unfortunately I have never worked with this veneer so I cannot give you any advise on its properties and difficulties.

You mention not enough glue with this veneer. If its an open grain wood you should see a small amount of bleed trough. If you are getting none then I would definitely increase the glue quantity.

Sincerely
Darryl Keil


 
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Loren Larson

Posts: 6

Joined: 2008-01-23
Location: Aurora, CO

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-29 11:51 PM
Post #34345 - In reply to #34344
Darryl,
Thanks for your input. One other thing that I haven't mentioned: for our repair efforts on the curved panel, we've been bagging the panel without the form. This seems to be working reasonably well. I haven't noticed any flattening of the panel - of course we're not using any other platen either. I have one more curved panel to veneer - both sides. Do you think I should do the initial veneering this way as well? That way I don't have to worry about matching the panel exactly on the form...
Thanks in advance.
Loren Larson


 
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Darryl Keil

Posts: 1455

Joined: 2003-05-22
Location: Maine

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Subject : RE: Delamination at seams and concave form, urea glue
Posted : 2008-01-30 1:08 PM
Post #34346 - In reply to #34345
Loren,

I don't see any problem veneering your curved panel without the form it was made on. I use the form because the addition of the veneer front and back can sometimes "lock" the curved panels shape more precisely to the forms radius. If your happy with the shape the curved panel is now, then its really no help to use the form.

Darryl
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