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.

310544

[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.

[John TenEyck]

Thanks for the vote of confidence Andrew. But as I mentioned earlier, I don't think my bathroom gets much humidity. Certainly there are swings when we shower, but the vent fan does a great job of removing moisture so there's never any condensate anywhere. But, OK, let's assume it was due to humidity swings. What would you do to overcome the problem? BB Ply with Unibond 800? I'm nervous about some future jobs, even though they are not for bathrooms, and want to take the most conservative approach.

John

[Mike Henderson]

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 know and it costs nothing.

John
I find that waiting and then stirring helps to reduce the lumps in the glue. Otherwise, it doesn't do anything.

Mike

[Chris Padilla]

You definitely sealed up the MDF with the ash and then further with the finish. It sure doesn't seem like a moisture issue. Are the panels that failed all still coplanar? I'm betting so.

So this leads to a glue problem that might perhaps be getting stressed from the slight moisture increase.

I don't edge glue my shop-sawn veneer panels either but I know David Marks does. I just pull them very tight with veneer tape. I usually get squeeze-out along this line so I figured that the edges are getting some glue.

Another stretch thought is possible contamination of a foreign substance around the veneer edges and so they didn't glue well and then are being stressed by the moisture.

My 1/16" shop-sawn walnut veneers on a double 5/8" MDF sandwich all glued with BetterBonds and vacuum pressed but not in a high-moisture environment tansu (http://www.sawmillcreek.org/showthread.php?92396-Tansu) is fairing well several years later.

[Andrew Joiner]

Thanks for the vote of confidence Andrew. But as I mentioned earlier, I don't think my bathroom gets much humidity. Certainly there are swings when we shower, but the vent fan does a great job of removing moisture so there's never any condensate anywhere. But, OK, let's assume it was due to humidity swings. What would you do to overcome the problem? BB Ply with Unibond 800? I'm nervous about some future jobs, even though they are not for bathrooms, and want to take the most conservative approach.

John

I torture test samples. Keep records of exact processes including finish.

[Pat Barry]

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.

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

310544
John, this looks great, too bad about the seam lines showing now. Its also too bad that the seams aren't coincident with the shallow dado's because then you wouldn't see anything at all. Having said that, where are the seams?

No doubt the issue you are experiencing though has something to do with moisture uptake and now drying out (in the ash). More so I think than moisture uptake in the MDF. Weldwood Plastic Resin Glue should be pretty stable against moisture when cured. It could be that those ash strips were just higher moisture content than you expected or they sucked the moisture out of the glue before it cured. It would therefore seem that an adhesive change might be the best fix for the next laminations you do

[John TenEyck]

Thanks Pat and every one else for your thoughts. I'll take some photos of the seams when I have a chance, so you can see what I'm talking about. At this point I think the best thing I can do is change to Unibond 800.

John

[Kevin Nathanson]

I don't think this one has been answered: Did you use a backing or balance veneer on the other side? Another thought; is the edgebanding moving and pulling or popping the seams apart?

K

[John TenEyck]

Yes, veneered both sides with the same stuff. Edges pulling? Doesn't look that way to me.

John

[Mel Fulks]

I looked for a copy of the older "let it sit" directions but did not find them. But in comments made by users I did see
several mentions of it being a good idea. From curiosity I would be compelled to glue up a sample in that manner using
the same materials and compare results.

[Kevin Jenness]

Your procedure seems correct, so it would seem that the conditions as installed must be drier than the fabrication conditions. Granted, bathrooms experience intermittent high humidity, but will fall back to whatever the prevailing humidity is in the house, which can be pretty low in our region in the winter. Do you have records or a recollection of the shop conditions at the time, and the ambient humidity of the house when the problem showed up?

Gluing the joints might have held them together under whatever stress they are experiencing. I usually glue joints on shopmade veneer, figuring the extra thickness will make the joints more prone to shrinkage at the surface.I don't know if I would want to use epoxy on ash as it can show a dark glueline on light woods and fill the grain on open grained ones, but one feature (good or bad) of epoxy in a vacuum press is that it will wick up through the joints and bond them if they are sawn or sanded. The same effect could be achieved with ppr by folding back and gluing the taped joints during the layup process, thus avoiding an extra step of pregluing and cleaning them up.

[John TenEyck]

My basement shop has been 30 - 40% RH all Winter. My house was in the 25 - 35% range during and after installation of the cabinet.

How would you fold back the joints and apply PRG during glue up without risking fracturing the veneer tape and still stay within the time window for open and clamp-up times? That just seems like a difficult and risky approach, as much as I like the concept.

John

[Kevin Jenness]

That doesn't seem like enough of a discrepancy to be a problem- and yet there is a problem that seems to be moisture related. I don't have the answer. You might try posting on the Woodweb veneer forum and the Vacupress forum ) for some more ideas.

I have not actually done what I suggested in one step; I have blue-taped seams, folded them back for gluing with pva and then cleaned up the joints prior to layup. It's hard to keep everything perfectly flush, though,if the veneer is not completely docile, thus my suggestion. I would use a heavy veneer tape, lay the taped sheet upside down, let the first leaf hang over the table edge to open the seam for gluing with a syringe, slide over to open the next joint and so on until the middle of the sheet, then slide over to the table's opposite edge to finish. It shouldn't add much more than five minutes to the process for a moderate size piece. The white (30 gram?) tape I usually use for sliced veneer might well not stand up to that, but I have some heavier Kraft paper tape that should with careful handling. It's always a good idea to do a dry run on something new like that before committing to it.

[John TenEyck]

Here's a photo of one of the seams that's opened enough that you (hopefully) see a white line of the underlying white ash.

310712

To answer someone's earlier question, the doors are still nice and flat. Not all the seams have opened, and of the ones that have, they have not opened across their entire length of about 22". More of the seams on the inside have opened than on the outside of the doors, but the veneer on the inside is narrower than on the outside so there are more seams.

Anyone have any additional thoughts?

John

[Kevin Jenness]

Two points, probably neither of which gets at the root of this problem.

1) substrate. Since having a drawer front laid up on mdf swell up at a corner adjacent to an improperly vented dishwasher, we have gone to Medex as a substrate for interior panels that may experience high moisture/humidity. It has the added advantage that the edges require no sizing for painted work, so we keep it in stock.

2) glue. Unibond is not free of water. I believe some of the water in the mix is replaced with alcohol, so it may reduce water-related issues, but not completely. Polyurethane adhesives may be worth experimenting with in this regard.