What is MDO plywood? What outdoor board does not warp? I am an artist working in stained glass mosaic. I currently use...

I am an artist working in stained glass mosaic. I currently use a iota board base but am worried about warp. I also want to create work that people can put outside - like on a deck or outside wall. What sign boards are oil lamp, sturdy, do not warp and are waterproof? And 1/2 or 5/8" thick, more or smaller number.
Broken terracotta tile removal cross-question?
Answers:    MDO is Medium Density Overlay on exterior plywood. it is used to make outdoor signs. needs ext primer and paint, follow next to spar varnish, or other ext topcoat.
Are full-size tiles easier to lay than smaller...
Ask for T- 1 eleven at home depot or lowes great for out doors and cheaper than marine plywood
My kitchen lights spawn my hot sink look...
i wouldnt use anything less than 3/4 surrounded by. marine plywood...