MDF vs baltic birch plywood....

[Ken Fitzgerald]

With respect to changes due to humidity, which is more stable, MDF or Baltic birch plywood?

Thanks!

[Doug Richardson]

I would think that the answer would be relative to how much humidity..... :D ..... relative..... humidity..... get it?

I would think that plywood would warp in areas of the country where the relative humidity is consistently high, whereas in that case the mdf would be more stable. However in 100% relative humidity, I would much prefer to be in a plywood boat.....;)

[Harvey Melvin Richards]

My experience has been that MDF will swell more, but Baltic Birch is much more likely to cup, twist, and warp. All of this is with nothing else fasten to the materials. I've also found that Apple Ply is better at staying flat than Baltic Birch is.

I do have a piece of 3/4" Baltic Birch that has been a bed liner in my truck for 9+ years. It has stayed very flat and this isn't the best situation for plywood. The truck does have a shell on it, but often reaches temperatures of 120°.

[Mel Fulks]

I like that answer. A rep for an exterior mdf told me their product would move about one third of one percent max with humidity changes .That might be more than plywood but probably more flat.

[Bill White]

Exterior grade MDF is a very stable product. It also make great jig material.
Made a dado fence for the TS from it, and it is a straight as a string (ok, a tight string).
Bill

[Roy Harding]

I live in a very humid area (Great Bear Rain Forest) - emphasis on the "Rain". Although I love it here, I did have some adjustments to make when I moved here from the MUCH drier Canadian prairie.

Since moving here about 6 years ago, I have come to rely on MDF more than plywood for various shop jigs, etcetera. I find that plywood sheets (no matter the grade/species/core material) warp, buckle, and twist - no matter how I store them. MDF, as someone above has already pointed out, will swell - but I haven't had any sheets twist or warp like the plywood.

[Mike Cutler]

I'd have to say MDF, even though I detest the stuff.
Don't believe that MDF won't warp or bow on you. It will, if left unsupported and exposed to moisture. In fact, it "bends" real nice given the right conditions. So does sheetrock.;)

[Alan Bienlein]

With respect to changes due to humidity, which is more stable, MDF or Baltic birch plywood?

Thanks!

Can you be more specific as far as how you plan on using it?

Example if I'm going to use veneer for lats say drawer or door fronts I'll use mdf as it's more stable while veneering plus the edges will be banded.
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Now if I'm gluing up veneer onto a substrate for a top I'll use Baltic birch because if some one spills something there's a bigger chance for damage do to moisture getting between the panel and the solid wood banding.
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[Ken Fitzgerald]

Alan,

I think you may have answered my question and I will use MDF I will explain.

A friend gave me some walnut that had been air dried for over 10 years. I was amazed how beautiful it is. I want to make a gift for him. It is small box using walnut with some birds-eye maple wrapped with black-white-black inlay on the top and the inside top. The plans call for birch plywood but the only 1/4" birch plywood I have been able to locate appears to me to be too rough to apply veneer over. I can find some 1/4" MDF that I believe would work better. The box is more of a keepsake box and I don't expect it to see harmful conditions.

My personal opinion of MDF vs plywood in general is this. If I had to use a material in structural circumstance where it might get wet, I'd probably use plywood. If I want something that needs a very smooth flat surface (like the table top for the router station I just completed) I would use MDF. I used 2 thicknesses of 3/4" MDF glued and screwed to give me a final thickness of 1 1/2" and then applied high pressure laminate to it. This was the first time I had ever worked with MDF.