Veneering question

[Keith Christopher]

Ok, I am getting into veneering so I have a question. I know you need to duplicate what you do to one side to the other. the question I have is what is the rule on this for the span. e.g. a 3'x2' span will need it but a 11"x9" won't.
I don't know if I'm fully understanding. I am stopping by the library however I just though I'd ask anyone who has done this. I'm using a vacuum press and right now I am experimenting. I can see this as being a VERY creative thing for me to do. Although I sometimes hate the thought of making furniture from plywood/mdf. I'm a purist sue me. :)

[George M. Perzel]

Hi Keith;
It depends on what you use as a substrate. I contend you don't need to veneer the reverse if you use MDF-no matter what the size (unless you want it for the aesthetics). To be safe, any wood core over 6" wide should have reverse veneered, especially if solid wood.
The purists will argue that everything should be reverse veneered, but that's why the pragmatists call them purists!
Good luck- veneering is a lot of fun and is rewarding.
George M. Perzel

[Keith Christopher]

I am really curious why you veneer both sides. I know there are humidors out there with only one face veneered and spans over 6". What is the downside to doing this. I know the rule is to add to both sides but what is the downside to not ?

[Chris Padilla]

You want the substrate to be exposed to the environment somwhat equally. If you veneer one side with whatever (say an Ash burl or something) and the other side is left open, you now have an imbalance in what the substrate will see as far as moisture absorption/loss goes. The thing could twist/warp on you. If the panel is captive in a frame, the frame might be strong enough to keep it flat...but maybe not.

Even MDF will absorb moisture over time and change. I have personally witnessed this on a workbench I made several years ago. It is mostly MDF but with the top surface laminated for wear and tear. Well, all those pieces are now slightly twisted. At the minimun, if it isn't practical (cost, time, lazyness) to laminate both sides, at least seal the one side not receiving the veneer (paint, poly, shellac, another cheaper veneer, etc.).

[Dave Brandt]

Chris, If that were true, wouldn't our kitchen countertops twist in the wind? There's usually plenty of moisture around them too. Not trying to start an argument, just never had a problem with laminated countertops moving. db

[Earl Kelly]

Keith, the Glue as well as the veneer can pull a cup or bow in a panel of any size. It's good practice to always balance your panels. Also, Please only use a urea resin glue or epoxy. These are far superior to PVA (titebond) glues. They make a rigid glue line, with no creep at the joints. A good source of info is the vacupress veneering forum.

[Mark Singer]

On MDF I seal the bottom with tung oil or whatever finish you use on top and your ok

[Chris Padilla]

Chris, If that were true, wouldn't our kitchen countertops twist in the wind? There's usually plenty of moisture around them too. Not trying to start an argument, just never had a problem with laminated countertops moving. db
Dave,

It depends on a lot of things. Yes, I've seen kitchen countertops twist before...it can be slight mind you. Believe it or not, plywood can move.

Kitchen countertops might be sealed by the virtue of cabinets being placed under them or perhaps their substrate is rather thick or the top (granite?) is quite heavy. I dunno but it is a good practice to seal one side when the other is sealed (in some fashion).

[Keith Christopher]

WOW thanks for all the info. I am looking forward to doing some veneering as I am making a humidor to silent auction for an upcoming charitable event. (it's a cigar event) here in baltimore. Well for somereason everyone wants a nice burl pattern on the outside of the spanish cedar. I have a bubinga slab I think I will cut veneers from and avoid any maple burls(common place with humidors these days) . I will surely post some images once it's done. I bought some cheap veneers to practice with so not to ruin any of the nice bubinga. the style design is done just need to get cracking !Thanks for all your help all.

[Chris Padilla]

Keith,

How about a nice walnut crotch? :)

http://www.sawmillcreek.org/showthread.php?t=7940

[JayStPeter]

Chris, If that were true, wouldn't our kitchen countertops twist in the wind? There's usually plenty of moisture around them too. Not trying to start an argument, just never had a problem with laminated countertops moving. db

A place I worked had desks custom made out of laminated MDF. They warped like crazy on the first batch. The second batch, they put some sort of thinner, cheaper laminate over the bottoms and those stayed. Look at most office furniture, the top is a laminate of some sort and the bottom is some form of cheap black "paper". This is to keep the bottom face from absorbing moisture while the top face doesn't. It's a humorous, but not pretty, sight seeing a bunch of geeks trying to use their computers on potato chip desktops.

I'm just guessing here, but I suspect the reason that kitchen counters don't warp is that they either:
1. spray some sort of clear finish coat on the bottoms, or
2. use some sort of particle board that is precoated or uses a moisture resistant glue. They are a little shiny on the bottom.

That said, I've built a couple of tops that were laminated that I didn't finish the bottoms of. They have worked OK, but both are bolted and/or glued to a pretty strong frame that holds them in place. I suspect if I somehow removed the top from the framework they would both warp. I guess the same is true for the humidors. If there's enough frame holding the laminated/veneered piece, it might be OK. Either that or there is some finish on the inside that keeps one face from absorbing more moisture than the other.

Jay

[Keith Christopher]

Must be the joinery then, because the inside *MUST* absorb water. It helps regulate the 65-70% humidity of the humidor.