That's planking, not plonking. Hopefully, this message will not end up
in everyone's killfile. ;-)

If you are cooking on a cedar plank (or any other wood), you want clean
untreated wood. The stuff sold as lumber for building decks and
furniture is often treated with bug or fungus repellants or other nasty
chemicals that you don't want in your food. The planks sold in a
grocery store, or in the BBQ department of a hardware store, are
probably OK.

This should be obvious, but who knows - maybe there are some people who
enjoy the taste of creosote.

--
Julian Vrieslander