I'm wondering what component in fertilizer contributes color to a pit fired ceramic piece.  Some fertilizers are more expensive than others, so I'm thinking that if I knew which component created color in a pit firing, I could price shop fertilizers without running the risk of buying a cheap fertilizer that is missing the agent needed.  Lots of folks on the Forum have mentioned Miracle Grow, but it's relatively expensive.  I'm hoping to find a cheaper alternative.... Jayne