Veneer Problems

[goskers]

Hello all,

I have run into a problem with some veneer. I used the PVA glue method for the first time because I used a non-backed, quilted maple and didn't want to take the chance of contact cement bleeding through.

After applying what I thought was decent amount of Titebond to the veneer I let it set. I then placed both the substrate and veneer together and used a medium temp iron with protection to bond the two together. I trimmed the veneer accordingly, eventually had it sprayed for finish and left it alone for about two months. No problems as of yet.

This is a small dress panel for a pair speakers that were not completely finished. This past weekend I went ahead and bonded the dress panels to the main cabinets. No sooner did I bond these two pieces together when I noticed bubbles in the dress panel where the veneer had lifted from the BB ply underneath. I dropped a few F-bombs and resourced the internet for options. Wikipedia stated that I might be able to fix the problem just like I applied the veneer the first time around. I have tried reheating the veneer and applying pressure with no luck.

I does not seem to have enough glue to bond the two pieces together now. Do I have any options?

[eyekode]

I have had this happen as well (even using the heat-lock stuff that is supposedly made for this). I managed to get mine to stick by re-applying heat.

I have heard you can also fix this by slitting the bubble and using a syringe to add more glue. How you keep this off the face of the veneer I have no idea . Note that glue does not stick to packing tape so you may be able to use this on a scrap piece of ply/MDF to apply pressure, sorta-like a cold press.

[Rolex]

You will want to be careful using an iron on non-backed veneer. This is not recommended. I found this out the hard way. I did a project this way that was crack free when finished. A few months down the road, there were major cracks over all surfaces. By major, I mean up to 4 or 5 inches long, all the way through the veneer. It was applied over MDF. Caul systems, or veneer presses are better choices with unbacked veneer.

There isn't too much you can do with an iron, now that your finish is applied. You may need to explore the option of reveneering the panel. Inserting a needle with glue into the bubble may work alright if you use weights or a caul system to hold the bubble down until it cures in lieu of the iron.

Anothe culprit could have been dust on the BB panel when you applied the veneer. If you had a small patch of dust, that would cause a bond break between adhesive and the substrate.

[JonW]

goskers,

I'm no expert, having only one iron-on veneer project complete. But one thing you said caught my eye. You added glue to the veneer. When I did my cabinets I added glue to the veneer AND the cabinets. Let those dry. Then added another later. Let dry. And then ironed-on the veneer. It's possible you didn't use enough glue in there. Good luck. We all know how frustrating these things can be.

-Jon

[Rolex]

Jon brings up a good point that I missed. At minimum with iron on, you at least want one coat of adhesive on both veneer and substrate. Two is better though.

[tktran]

I've had this exact same problem too, on the very first pair of speakers that I built. I have no idea how to fix it, because by the time I discovered the problem, the veneer was already oiled and waxed.

Since then, I've built several other speakers, all veneered. I no longer let my speakers sit exposed to the sun (the first speaker had direct sunlight every afternoon for 6 months). I now avoid raw veneers, instead I use only use paper backed veneers. I also give the MDF 2 coats of the PVA glue, and the veneer 1 coat.

AND I'm extra careful when it comes to ironing and inspecting for lift prior to finishing...

[technimac]

I feel your pain.....

I had essentially the same problem with raw heavy flaked white oak veneer. Unfortunately there were over 20 "voids" on the top of this project ). :M

The solution I came up with was as follows:
Slice the along a dark part of the grain (in the middle of the bubble), gently lift one side, then slide a syringe (loaded with PVA glue) under and deep into the void, then fill it with glue.
Repeat the procedure for the other side of the bubble.
Squeegee out the excess glue (through the slit) and clean off the surface with a damp cloth.
Clamp the whole area for at least 24hrs, then continue with finishing.

This worked well for me, but I abandoned the hot iron/PVA method for raw veneer after that.
BTW Here's how the final product turned out:



FWIW Here's a link to the process I used for the remaining nine speakers that are finished with the same veneer:

https://www.htguide.com/forum/showpost.php?p=294704&postcount=19

HTH,
Bruce

[Richard.C.]

always the easiest way, get a thicker veneer, 2,3mm. add generous amount of pva and even clamp firm and even. with thicker venner you wont get bleed through either and holds better.

[JonP]

goskers,

I'm no expert, having only one iron-on veneer project complete. But one thing you said caught my eye. You added glue to the veneer. When I did my cabinets I added glue to the veneer AND the cabinets. Let those dry. Then added another later. Let dry. And then ironed-on the veneer. It's possible you didn't use enough glue in there. Good luck. We all know how frustrating these things can be.

-Jon

I have just done a couple.. so no expert here either. But I wanted to underline what Jon said...

My first project was with a nice, Sapele veneer I got for a good price. It was unbacked and pretty thin.

I ended up with good results, but had tried a few test pieces beforehand, and that taught me that it was important to have a good layer of glue on both sides. All my problems were basically due to insufficent glue. Luckily I had enough on the actual boxes. No bleedthru either.

Another thing, after reading about JonMarsh's method of doing large panels with a hot and cold iron, I used a hand sized block of MDF as a "cooling press" behind where I ironed.. pressing down the glue while cooling. This seems to reduce the tendancy for the veneer to lift, and you end up with a better bond.

A later project was with a paperbacked Mahogany... easier, the wood was much more flexable as well...

I'd guess it varies a lot, depending on the particular wood, how flat it wants to lay, vs how wavy it wants to go... how porous it is or isnt... etc.