I'm looking to make a fairly large sign/logo to go on an outdoor wall, but I'm not sure what to make it from.
I'm fairly handy with mdf - easy to cut and shape - so would sealing and painting it make it suitable for outdoors and exposed to the elements?
Plywood seems like it would be tough to smooth off.
Acrylic was another thought, but I don't know where to buy a large piece of it - approx 500mm x 1000mm.
Don't use regular mdf. It is not an outdoor material. They now make a mdf product that claims to be for outdoor use, but it doesn't have a track record, and I would not trust it until is has proven itself. Anyone remember the fantastic marketing claims of Masonite brand siding in the 70's? Literally tens of millions of feet were installed on houses before it all starting disintegrating from moisture a couple of years later.
Like suggested, locate some mdo. It is tough stuff and very smooth finish. Next choice would be a piece of MARINE grade plywood coated with three coats of epoxy resin.