Veneer seams opening

[John TenEyck]

I built a new vanity for my bathroom using 1/16" shop sawn white ash veneer on MDF. Two months after installation I'm starting to see some of the seams open up a little. The wood was kiln dried and had been in my shop for months; the MDF for a couple of weeks. I used Weldwood Plastic Resin Glue, applied with a foam roller using the recommended coverage, and had the panels in the vacuum bag for 8 hours at 100F IIRC (in any case, more than enough time @ temp.). Any ideas what happened? Just as important, how do I prevent this from happening again?

John

[Mike Henderson]

Couple of questions, John.

1. What was the substrate?
2. Are you sure there was no tape of any kind on the glue face?
3. Was the ash face sawn or quarter sawn?

Mike

[John TenEyck]

Couple of questions, John.

1. What was the substrate?
2. Are you sure there was no tape of any kind on the glue face?
3. Was the ash face sawn or quarter sawn?

Mike

Mike, 3/4" MDF substrate. Both sides of the veneer had been drum sanded to 120 grit. There was absolutely no tape on the glue face. The seams were cross taped with veneer tape and then fully taped on the show side. The ash was rift sawn, in the range of 4 to 6" wide.

The glue was about a year old now that I think about it, but it mixed OK and cured hard. Just thought I'd add that to the mix.

John

[Mike Henderson]

I doubt if it was the glue. I've used UF glue that old and never had any problems.

I just don't have any ideas. When you use a water based glue, the veneer can expand from the moisture but Riff sawn ash usually doesn't change a whole lot. But that's about all I can offer. Sorry.

Mike

[This won't help here but someone suggested to me that I glue shop sawn veneer seams together before laying. Put a bit of titebond on the edge and pull it together with blue tape. When cured, lay. No idea if it will help - I haven't had the opportunity to try it yet.]

[John TenEyck]

Thanks Mike. I have no clue either. And I've had people recommend gluing the seams first, too. It always seemed like an unnecessary extra step, but maybe it's time to try it.

John

[Mel Fulks]

If the glue mixed well and cured well then age is not a factor. It definately spreads and works better if you let it sit for ten
or fifteen minutes before spreading ,that used to be written on the label. Can't think of anything that caused the shrinkage
but I would be suspicious of the heat, anything 70 or above is plenty.

[John TenEyck]

Hmm, the heat. Let's discuss. Why would you be suspicious of that? 70F takes like 13 hours to cure, as little as a couple of hours at ?? F (can't remember). I wanted to speed up the process so I used the heating blanket. I think I've read of others doing it. Are you thinking that somehow made the glue set but the veneer still had moisture and then later shrank as that moisture evaporated? Don't know, seems like a long shot since it took 2+ months before the problem showed its ugly head. Any hypothesis is good at this point, though. I just wish I could get to the bottom of it - I have more veneer jobs ahead, for customers, and can't afford failures there. Guess I'll leave out the heating blanket.

Thanks.

John

[Don Kondra]

What did you use for a finish John ?

For a bathroom, you may want to consider switched to a Baltic or Apple Ply core in the future...

Cheers, Don

[Chris Padilla]

I assume both faces of the MDF were covered. Were all the edges covered and or sealed well? Personally, I would keep MDF far from a bathroom or a kitchen unless well sealed and even then, I'd use it as a last resort. Any pics?

[Mike Henderson]

Try a non-water based glue. Perhaps the water in the glue is causing the veneer to swell and over time the moisture equalizes and the veneer shrinks. Unibond 800 is non-water based, I believe. Has a short shelf life so don't buy more than you can use.

Mike

[John TenEyck]

Hi Chris, I ran a strip of ash about 1/2" wide around all the edges of the MDF first, then veneered both sides. After trimming it looks almost like a solid wood door. The doors are finished with a shellac toner and then 3 coats of GF's Enduro Clear Poly.

Personally, I have no problem using MDF in a bathroom, at least in mine. There is a vent fan and we never have condensation on anything after taking showers. I choose MDF over BB Plywood because I thought it might be a bit more stable.

Mike, maybe going to Unibond 800 is a good idea. I like Weldwood PRG because I can get it locally, but if Unibond 800 stops this problem I'm happy to switch.

John

Here's a pic of the doors during installation. The veneer seams are not where those shallow dados are.

IMG_3637.JPG

[Mel Fulks]

John, suspicious just because I can't think of anything else ....I mean,somebody already got the mdf swell angle. I do
think the glue benefits from the brief rest after mixing, it definately changes it. On some surfaces,especially things like
italian bending ply, the glue will kind of bead up missing some places and require more brushing,after the rest it goes
on smoothly even though viscosity seems exactly the same. I read a mention years ago about some of the ingredients
taking longer to dissolve ,but that might have just been the writer's guess.

[John TenEyck]

Thanks Mel. I never wait after mixing, but certainly can do so and then remix. I've never had a batch that didn't cure really hard, so it's hard to believe it wasn't mixed sufficiently, but you never no and it costs nothing.

John

[Mel Fulks]

I think they took that step off the label simply because it might have seemed an annoyance to customers reading labels
in store and wanting "quickest" way to get job done. And I agree most people didn't rest the stuff anyway. Have seen some work mates adopt it when they saw it did make spreading easier.

[Andrew Joiner]

John I think you did everything right. I have laid up 1/16" shop sawn veneer without edge gluing and had no joints open up, but it's not in a bathroom.
Bathrooms of course push the limits of even the best woodwork. Humidity extremes can cause lots of problems that would never show up in normal conditions.