What do I make these shelves out of?

[Brian Brown]

Not sure if this should go here or finishing, but I'll try here first. I'm working on a Honey-do for SWMBO. We have put bead board 6' up the walls of our guest room, and she wants shelves running along the top of the bead board. The shelves will be about 8" wide, and will be painted white. I'll use pressed MDF crown molding from the BORG at an angle under the shelf for decor/support. I thought about making the shelves out of MDF for cost and ease, but I find the cut or routed edge is very rough when painted. Even if it is smooth to start with, it absorbs moisture from the paint, and swells. I could use poplar or alder, but both are expensive here. Do you have any other thoughts, or is there a good way to seal the edge of the MDF to keep it smooth when painted? Normally I use hardwoods for the beauty of the grain, and I rarely paint anything, so this one is beyond me. Thanks for the help.

[Joe Scharle]

First, MDF will sag under it's own weight. Second, I rub yellow glue into the cut ends with my finger. Sand smooth & paint. Try it on a piece of scrap.

[Brian Brown]

I have heard that you can paint thinned Elmer's white glue on the edges, sand and paint, but I don't know how well it works. Anyone with experience? As for the sagging, I think they will be well supported. I have plans for an interior structure with lots of support.

[David Christopher]

Brian, you can use sanding sealer to the edges of MDF and it will take care of the roughness...but I think I would use something else for the shelfs, maybe pine shelving board if it is avalible

[Brian Brown]

Pine was my first thought, but everything I can find here is green. Apparantly Home Depot defines kiln dried as 22% MC. You can wring the stuff like a sponge. I called a lumber yard a few minutes ago, and I'll take my moisture meter down and check their "Dry" stock, but the salesman said "it may need some drying time". Anybody know an internet source where I can get some dry pine reasonably priced?

[Robert Reece]

My local lumber yard sells pre primed finger jointed trim material that is awesome. The primer is a mile thick and the finger joints are not detectable. I think it's called protrim or Xtrim. You might use this. It's comes up to 1x12 and 16' long. I believe the wood is radiata pine, which is fairly hard and stable. If you can't find this preprimed material, you might ask for radiata pine. It's pretty good stuff.

Second, I don't care much for MDF, so I tend more towards preprimed plywood and then I apply the profiled edge with biscuits and glue or just glue. You can use tape to apply this edging if you don't have enough clamps. If you can't find preprimed ply, then just use a good quality cabinet ply and prime it yourself.

[David Dockstader]

If you go with MDF, I find covering the edges with joint compound (yup, the stuff for wallboard) and then sanding it down does a pretty good job of sealing the edges and making it smooth.