If you want some real chemical fun, grab some ferric chloride (etching fluid). I used this to pit and blacken my old imai Elefant tracks and some other items over the years. You do need to wear a mask and use gloves as well as being in a ventilated room. To stop the reaction you use a water and baking soda bath. It's pretty fun as the reaction generates heat and you can see the results happen right in front of your eyes. Real mad scientest stuff!! Like I said though, handle with care. Check around for best price on amazon or ebay.

https://www.amazon.com/MG-Chemicals-...erric+chloride