Veneer

You are not logged in. [ Login ] Why log in
(NOTE: Login is not required to post)

Veneer bubbles 5 years later...help

4/28/13       
Ken Irish  Member

Website: http://www.direys.com

The photos show the concave side of a curved face (back) mdf audio speaker. I have pressed veneers with Unibond 800 and the Vacupress for the last 15 years. This is the first job I have had come back to me. These speakers have been kept in a climate controlled room without excessive heat or sunlight. (I understand the room is filled with about 750K of audio equipment which makes me believe that excessive environmental variables are not the problem.) This condition occurs only on the concave face of both speakers. The convex faces, veneered at the same time, same glue, same species, same finish show no problems. Nor does a flat veneer job on a nearby woofer box. (veneer direct to mdf) I paper taped and pressed the Pau Ferro veneer to the brown paper backing by Neenah (http://www.neenah.com/technical/heirloomfurniturecomponents/veneerbacker.aspx)and
then pressed the paper and veneer two ply to the mdf core in a separate pressing. It seems the only difference in application or materials or use and exposure to elements is the convex vs. concave variable. That seems to suggest it has possibly something to do with the nature of compressing the veneer along an interior curve vs. expanding the veneer over an exterior curve. Doesn't make much sense to me. Given that the lifts are clearly related to the grain pattern it seems clear the issue occurs between the veneer and the paper. The paper to substrate lamination looks solid. We're going to tear this off and do it again and I'd like to minimize the possibility of this happening again. I'd sure appreciate your communal wisdom. Thanks for your help.


View higher quality, full size image (1024 X 681)


View higher quality, full size image (1024 X 681)


View higher quality, full size image (1024 X 681)

4/29/13       #2: Veneer bubbles 5 years later...help ...
John Van Brussel

Website: http://www.veneersystems.com

How did you glue the paper backing to the veneer? Did you use raw paper back or glue one side paper back. Most paper back is pressed at 150psi with a min. temperature of 250F. These aren't bubbles but surface checks in the veneer. 99% of the time these surface checks are moisture related. What type of finish did you use? Water based or solvent?

4/29/13       #3: Veneer bubbles 5 years later...help ...
Rich

Why the paper? What do you expect from this added step that you won't get from bonding directly to the MDF? Is that the seam I see where it is slightly curled over the entire length? Sure does look like moisture, but maybe some of that is knife cracks from the veneering process? Maybe consider that knife checking when choosing the side to face the MDF.

4/30/13       #4: Veneer bubbles 5 years later...help ...
Charles  Member

Website: http://www.northcreekwoodworks.com

Random stuff:

Not sure what Unibond is made of, but with hard veneers like Pau Ferro, a resin glue never moves. Heat can effect PVA glue even after hot pressing/ catalyzing. Paper moves more than you might think. Movement creates stress, stress creates fissures.

5/1/13       #5: Veneer bubbles 5 years later...help ...
Dave

From the Neenah link: "Compatible with - Contact glues - water-based emulsion glues - hot-melt adhesives"

"I paper taped and pressed the Pau Ferro veneer to the brown paper backing"

If you flat pressed them together with Unibond 800, that's the cause. I also don't understand the use of paper, but I would definitely use PVA for the paper to veneer joint.

5/1/13       #6: Veneer bubbles 5 years later...help ...
Ken Irish  Member

Website: http://www.direys.com

Thank you for your thoughtful responses. We pressed the pau ferro to a paper backing with Unibond 800, a urea resin cold press glue. The paper adds strength to the veneer when pressing over a curved substrate, especially the concave substrate. We did not use the paper on a nearby square, flat woofer box. It shows no problems. But the convex curved faces of both speakers we used the paper backing and also show no problems. Either by chance I treated the two 2-ply (paper and veneer) differently that I used on the front from those I used for the backs. I think I glued all four 2 plies at the same time so it would be just chance that two bad ones ended up on the backs and two good ones ended up on the front. We used a conversion varnish finish on all faces, applied at the same time, same manner. I am requesting better pictures from the customer and will repost if I learn something. It looks environmental to me but I am certainly open to another explanation. Thanks

5/1/13       #7: Veneer bubbles 5 years later...help ...
Ken Irish  Member

Website: http://www.direys.com

John,
We used raw Neenah paper as per the Yorkite that I have used for years. I'm assuming (silly me) that it had the same application standards as the Yorkite. I need to talk to my finisher, but I'm quite sure we used a solvent based conversion varnish. Your 99% comment coincides with my first impression for this kind of defect though I have been told that the room "contains $750,000 of audio equipment." making me think the temp and moisture would not be wildly erratic. I have been considering the possibility of air conditioning vents at the back of both speakers. I'll ask more questions. Thanks

5/3/13       #8: Veneer bubbles 5 years later...help ...
John Van Brussel

Website: http://www.veneersystems.com

Ken,

When the kitchen cabinet door manufacturers first started membrane pressing the raised panel inserts there were a lot of issues when using straight UF resins. The solution was to blend in up to 35% PVA and 5% Melamine into the UF glue. You retain the thermoset glue line with the 65% UF content, the PVA makes the glue line more flexible and the Melamine gives a higher water resistance.

The stresses between the paper and the veneer could be causing your glue line to crack and this could be transferring to the wood.

5/3/13       #9: Veneer bubbles 5 years later...help ...
Dave

And what's between the paper and veneer appears to be a rigid glue line that was put into compression when the flat 2 ply lamination was applied to a concave shape. Plastic resin is great for bent laminations that you don't want to flex, its not a good choice for flat laminations that you plan on bending.

5/11/13       #10: Veneer bubbles 5 years later...help ...
Andrew Kelsey Member

Website: http://www.kelseyfinewoodworking.com

This is just a wild idea, but I thought I would through it into the mix.

The damage to the veneer really looks like moisture damage to me. That damage occurs because the veneer swells with moisture and pushes up like a mountain range.

So why the difference between the convex and concave. The concave is already compressed and that leaves no room for the expanding veneer to go. The convex side is in tension, so there is some space for the veneer to move to when it expands.

5/12/13       #11: Veneer bubbles 5 years later...help ...
B.H. Davis Member

We had some bending ply core baseboard delaminate a couple years ago on the concave side of of a curved wall. The convex side was fine.

We had a double layer of 1/8" thick white oak veneer applied to the face of a double layer of 3/8" bending ply. As the oak shrunk with moisture change it remained stable on the convex side because shrinkage just pulled it tighter to the curve. On the concave side though shrinkage allowed the oak to move away from the wall surface thus putting pressure on the bending ply layer structure. The grain direction was going length wise down the wall so that the only shrinkage involved was over the 4" width of the material. In effect the oak was able to curl away from the wall.

One could consider that the same was taking place here. If the wood had been glued direct to the MDF substrate there would have been no way for it to move. My guess is the paper backer was the weak link much as our bending ply. It acted as an weak barrier between veneer and MDF allowing for the veneer to surface to move and fail.

Think of the paper barrier's strength in terms of paper being used in a joint where the surfaces are going to have to be separated later..... like when mounting blanks for turning on a lathe. Paper is put between the two because it will split on center when the two wood parts are split apart with a chisel.

Even in a climate controlled space there will be some moisture variation over a 5 year period. Perhaps a different veneer wood species would have been more forgiving in this situation. I suspect the paper allowed for enough wood movement to stress the grain structure, thus resulting in surface failure.

BH Davis

5/18/13       #12: Veneer bubbles 5 years later...help ...
jimbo

We had some paper backed Maple veneer on a flat surface do this same thing. The company that supplied the veneer tried blaming the finish. It wasn't the finish.


Post a Response
  • Notify me of responses to this thread
  • Subscribe to email updates on this Forum
  • To receive email notification of additions to this forum thread,
    enter your name and email address, and then click the
    "Keep Me Posted" button below.

    Please Note: If you have posted a message or response,
    do not submit this request ... you are already signed up
    to receive notification!

    Your Name:
    E-Mail Address:
    Enter the correct numbers into the field below:
     

    Date of your Birth:



    Return to top of page

    Buy & Sell Exchanges | Forums | Galleries | Site Map

    FORUM GUIDELINES: Please review the guidelines below before posting at WOODWEB's Interactive Message Boards (return to top)

  • WOODWEB is a professional industrial woodworking site. Hobbyist and homeowner woodworking questions are inappropriate.
  • Messages should be kept reasonably short and on topic, relating to the focus of the forum. Responses should relate to the original question.
  • A valid email return address must be included with each message.
  • Advertising is inappropriate. The only exceptions are the Classified Ads Exchange, Machinery Exchange, Lumber Exchange, and Job Opportunities and Services Exchange. When posting listings in these areas, review the posting instructions carefully.
  • Subject lines may be edited for length and clarity.
  • "Cross posting" is not permitted. Choose the best forum for your question, and post your question at one forum only.
  • Messages requesting private responses will be removed - Forums are designed to provide information and assistance for all of our visitors. Private response requests are appropriate at WOODWEB's Exchanges and Job Opportunities and Services.
  • Messages that accuse businesses or individuals of alleged negative actions or behavior are inappropriate since WOODWEB is unable to verify or substantiate the claims.
  • Posts with the intent of soliciting answers to surveys are not appropriate. Contact WOODWEB for more information on initiating a survey.
  • Excessive forum participation by an individual upsets the balance of a healthy forum atmosphere. Individuals who excessively post responses containing marginal content will be considered repeat forum abusers.
  • Responses that initiate or support inappropriate and off-topic discussion of general politics detract from the professional woodworking focus of WOODWEB, and will be removed.
  • Participants are encouraged to use their real name when posting. Intentionally using another persons name is prohibited, and posts of this nature will be removed at WOODWEB's discretion.
  • Comments, questions, or criticisms regarding Forum policies should be directed to WOODWEB's Systems Administrator
    (return to top).

    Carefully review your message before clicking on the "Send Message" button - you will not be able to revise the message once it has been sent.

    You will be notified of responses to the message(s) you posted via email. Be sure to enter your email address correctly.

    WOODWEB's forums are a highly regarded resource for professional woodworkers. Messages and responses that are crafted in a professional and civil manner strengthen this resource. Messages that do not reflect a professional tone reduce the value of our forums.

    Messages are inappropriate when their content: is deemed libelous in nature or is based on rumor, fails to meet basic standards of decorum, contains blatant advertising or inappropriate emphasis on self promotion (return to top).

    Libel:   Posts which defame an individual or organization, or employ a tone which can be viewed as malicious in nature. Words, pictures, or cartoons which expose a person or organization to public hatred, shame, disgrace, or ridicule, or induce an ill opinion of a person or organization, are libelous.

    Improper Decorum:   Posts which are profane, inciting, disrespectful or uncivil in tone, or maliciously worded. This also includes the venting of unsubstantiated opinions. Such messages do little to illuminate a given topic, and often have the opposite effect. Constructive criticism is acceptable (return to top).

    Advertising:   The purpose of WOODWEB Forums is to provide answers, not an advertising venue. Companies participating in a Forum discussion should provide specific answers to posted questions. WOODWEB suggests that businesses include an appropriately crafted signature in order to identify their company. A well meaning post that seems to be on-topic but contains a product reference may do your business more harm than good in the Forum environment. Forum users may perceive your references to specific products as unsolicited advertising (spam) and consciously avoid your web site or services. A well-crafted signature is an appropriate way to advertise your services that will not offend potential customers. Signatures should be limited to 4-6 lines, and may contain information that identifies the type of business you're in, your URL and email address (return to top).

    Repeated Forum Abuse: Forum participants who repeatedly fail to follow WOODWEB's Forum Guidelines may encounter difficulty when attempting to post messages.

    There are often situations when the original message asks for opinions: "What is the best widget for my type of shop?". To a certain extent, the person posting the message is responsible for including specific questions within the message. An open ended question (like the one above) invites responses that may read as sales pitches. WOODWEB suggests that companies responding to such a question provide detailed and substantive replies rather than responses that read as a one-sided product promotion. It has been WOODWEB's experience that substantive responses are held in higher regard by our readers (return to top).

    The staff of WOODWEB assume no responsibility for the accuracy, content, or outcome of any posting transmitted at WOODWEB's Message Boards. Participants should undertake the use of machinery, materials and methods discussed at WOODWEB's Message Boards after considerate evaluation, and at their own risk. WOODWEB reserves the right to delete any messages it deems inappropriate. (return to top)


  • Forum Posting Help
    Your Name The name you enter in this field will be the name that appears with your post or response (return to form).
    Your Website Personal or business website links must point to the author's website. Inappropriate links will be removed without notice, and at WOODWEB's sole discretion. WOODWEB reserves the right to delete any messages with links it deems inappropriate. (return to form)
    E-Mail Address Your e-mail address will not be publicly viewable. Forum participants will be able to contact you using a contact link (included with your post) that is substituted for your actual address. You must include a valid email address in this field. (return to form)
    Subject Subject may be edited for length and clarity. Subject lines should provide an indication of the content of your post. (return to form)
    Thread Related Link and Image Guidelines Thread Related Links posted at WOODWEB's Forums and Exchanges should point to locations that provide supporting information for the topic being discussed in the current message thread. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related Link that directs visitors to an area with inappropriate content will be removed. WOODWEB reserves the right to delete any messages with links or images it deems inappropriate. (return to form)
    Thread Related File Uploads Thread Related Files posted at WOODWEB's Forums and Exchanges should provide supporting information for the topic being discussed in the current message thread. Video Files: acceptable video formats are: .MOV .AVI .WMV .MPEG .MPG .MP4 (Image Upload Tips)   If you encounter any difficulty when uploading video files, E-mail WOODWEB for assistance. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related File that contains inappropriate content will be removed, and uploaded files that are not directly related to the message thread will be removed. WOODWEB reserves the right to delete any messages with links, files, or images it deems inappropriate. (return to form)