On Monday, February 10, 2020 at 3:21:15 PM UTC-8, Ivan Vegvary wrote:
Tearing out sagging shelves in a 10ft. by 6ft. pantry. Would jike to put 18" deep shelves on the back wall. These would not be "cabinet" quality construction.
So, rip 18" wide plywood? Particle board? Bisquit join solid lumber?

Solid is the strongest, and you have the option to put a pretty wood on the leading edge.
Knotty softwood is the inexpensive way to go (vinyl surface
can be applied so the occasional leaky can won't hurt the wood). Biscuits are good.

Particle board will creep-sag with time, don't believe the 'sagulator' predictions. Plywood
is weaker than solid wood (half the grain runs the wrong way).

Uprights in plywood (it's tough) but be sure the glue is exterior; spills happen. If you
can stagger shelves, so the dados don't thin the uprights, that's a win.

A full-gallon pickle jar is under 12 inches.