veneer over plywood substrate question

[Bruce Mack]

I will be applying shop sawn veneer to both sides of a 9 mm. panel of baltic birch. While understanding that plywood is made of an uneven # of plies with alternate grain direction, I wonder if my add-on veneer should follow that cross grain construction or should be applied in the same direction as the underlying ply to avoid micro splitting from later wood movement. Clearly commercial plywood makers have dealt with this in their choice of glues, heat, and pressure. However, I will be using PVA glue and a hand iron, so my question may be relevant. Or is it quibbling?

[Jerry Wright]

9mm veneer seems awfully thick to be gluing onto immovable plywood. The veneer will expand and contract. The substrate will not. IMHO

[mreza Salav]

PVA isn't the preferred glue as the water in it will make the veneer deform. If you apply a uniform pressure to surface you can limit this issue.
As long as your veneer is thin enough I don't think it would matter much which direction you apply it.

[Bob Cooper]

I think he’s saying the plywood is 9mm

[Jamie Buxton]

The important thing is to make a balanced panel. The two applied veneers should go the same direction.

[Richard Coers]

Thickness of your shop sawn veneer is critical. I was taught to use 3/32 thick and then sand smooth to near 1/16" final thickness. Go thicker and the shop sawn veneer will act like solid wood and continue with seasonal movement.

[Kevin Jenness]

Your face veneers should be perpendicular to the plywood layer underneath. The Baltic Birch layers are pretty thick and often checked, if you add more thickness parallel to the substrate you are more likely to have face checking.

[John TenEyck]

I've done it both ways and have never had a problem. I always thought it best to go cross grain but then I was faced with having to make a 7 ft veneered table top so I had no choice but to put the veneer in the same direction as the plywood layers. That table is at least 6 years old now and still doing fine.

FWIW, there's no hard and fast rules as to what constitutes veneer. Commercial stuff is ridiculously thin. On the other hand, I've used shop sawn "veneer" 1/4" thick on exterior doors. They all work. Most of the time I use 1/16" shop sawn veneer for interior projects. It just seems like a happy medium of easy to work with, durable, and good yield from the lumber.

Have you tried the iron on approach on 1/16" veneer? I've never done it with stuff that thick.

John

[Warren Lake]

Its cross grain. Thats why cut to size people have plywood with grain running crossways. Its done that way so the veneer layer then runs lengthways. They are full time veneer suppliers to shops in whatever custom way and core people need.

Solid ive asked some pros and still see them running with the grain. Its harder to do with solid if it is even a rule for solid. I not so sure it is. There is tons of past fancy veneer work. This should not be your first project

482688

[Bruce Mack]

I think he’s saying the plywood is 9mm
Yes. My veneer after scraping is about 1/16". I think imperial measurement but I see that I confused things by using the metric plywood measurement rather than the 3/8" accepted US equivalent.

[Maurice Mcmurry]

I think balance is most important. If you have an odd number of ply's the layers on each side of the core should match. If you have an even number of ply's all of the ply's should match their counterparts (from the center outward).

[johnny means]

We run our 1/8" veneers which ever way gets us what we need. Never have a problem. The most important thing is a really good bond onto a structurally sound substrate. Baltic birch should do the trick. Your application method seems inadequate. You really need to be able to keep the veneer pressed until the glue is completely dry.

[Kevin Jenness]

The rules about laying face veneers at right angles to the previous layer and maximum veneer thickness are like a highway speed limit. You can often break the rule without a problem, but your chances of failure go up. Compound the issue by using thick veneer parallel to the underlying ply with a less than optimal gluing technique and success is less likely.

[Bruce Mack]

We run our 1/8" veneers which ever way gets us what we need. Never have a problem. The most important thing is a really good bond onto a structurally sound substrate. Baltic birch should do the trick. Your application method seems inadequate. You really need to be able to keep the veneer pressed until the glue is completely dry.
I have read some articles about using dried PVA on both veneer and substrate. Mario Rodriquez (FWW Sept/Oct.1994) wrote about this and endorsed the technique. He veneered all surfaces of a demilune table using Titebond II and a hand iron. I'm not Mario Rodriquez but my project is just a serving tray. I will begin with a sample of my curly oak and see whether I can make a 4 1/2" x 22" strip fully adhere.

[Warren Lake]

you get away with stuff because you are small shops. When people are doing massive amounts of veneers supplying to tons of customers they stick to what has been known and proven for 1000 years as they cant afford to have some small percent of stuff crash and burn. The law suits are just not worth it.

[Bruce Mack]

Excellent observation. As an amateur and a first-time veneerer I've failed dismally once and expect failure this time too. Vacuum bags and wet glue veneering are beyond me.

[Kevin Jenness]

It's not that complicated. A small project like that can be pressed with a few clamps and cauls sufficient to get even pressure across the surface. Getting enough heat to the glueline through thick veneer with an iron without causing problems will be a challenge. Why do it the hard way?

[Warren Lake]

vacuum bag is not complicated and it works well, yes it can fail if issues in your set up or application. I had a test one fail once but it was a test and the issue was not getting enough vacuum.

Ive never done the iron thing but I do iron my shirts and did stay at a Motel 6 once. The iron thing is new to me didnt exist or us know about it back 40 years ago. Did I not hear that some of that iron on stuff had been failing?

[Bruce Mack]

vacuum bag is not complicated and it works well, yes it can fail if issues in your set up or application. I had a test one fail once but it was a test and the issue was not getting enough vacuum.

Ive never done the iron thing but I do iron my shirts and did stay at a Motel 6 once. The iron thing is new to me didnt exist or us know about it back 40 years ago. Did I not hear that some of that iron on stuff had been failing?

I'm not necessarily trying to convert you, Warren, but this is a photo from today of a 1/16" test cut from softwood which I ironed to baltic birch 1 month ago. The cut is rough and I did not scrape or otherwise smooth the side in contact with the plywood. I used Titebond II and let it dry 2-3 hours before ironing it. It stuck quickly and I see no evidence of separation at the margin.

[Warren Lake]

I just have no experience with the iron thing and non of the old guys i knew ever mentioned it.

I learned if I stay in one place too long on my dress shirts though that people will ask what is that on my shirt. It sounded sensible to me same principle sort of as an edge bander then years later someone told me about failures but dont know who. Id like to think it works fine and good for life.

[Sean Nagle]

I'm not necessarily trying to convert you, Warren, but this is a photo from today of a 1/16" test cut from softwood which I ironed to baltic birch 1 month ago. The cut is rough and I did not scrape or otherwise smooth the side in contact with the plywood. I used Titebond II and let it dry 2-3 hours before ironing it. It stuck quickly and I see no evidence of separation at the margin.

That's impressive. I have veneered numerous MDF loudspeaker cabinets using the iron method without a single failure. However, I used paper-backed veneer with Titebond original, not shop-sawn veneer.

[Bruce Mack]

I just have no experience with the iron thing and non of the old guys i knew ever mentioned it.

I learned if I stay in one place too long on my dress shirts though that people will ask what is that on my shirt. It sounded sensible to me same principle sort of as an edge bander then years later someone told me about failures but dont know who. Id like to think it works fine and good for life.
I am new to veneering and really don't think I'll have occasion to do it again. The iron-on method with dry positioning of the pieces does not necessitate veneer tape and vacuum bag and seems to have less "opportunity" for failure in my hands. There are only three 4 1/2" strips of veneer on each side, so ​what could go wrong? :eek:

[Bruce Mack]

That's impressive. I have veneered numerous MDF loudspeaker cabinets using the iron method without a single failure. However, I used paper-backed veneer with Titebond original, not shop-sawn veneer.
Thank you, Sean. I'm a blundering amateur. The serving tray began as a gift for a friend. Since I expressed that intention, her daughter has become critically ill. Somehow I hope that the hand scraping and other irregular work will translate as a tribute and a prayer for them. I expect no resolution but want to add this magical thinking to the gift.