N.G.
When my son was about 16 mos he did the same thing. I was convinced he would poison himself by eating the wood-stain! After about two months I ended up putting him in a double bed with plastic rails (because I was pregnant and needed the crib anyway.) Voila! I don't know if this is reasonable for you to do, but from experience I can tell you that 18mos is definitely old enough to move him out of the crib if you need to.