|To perform the final polish, take a look at the rocks which remain and put aside any which are damaged with chips or are not generally the shape you like. You can always place these into another batch tumbling session with the same kind of rock, where they will take on a new form during step 1. This way nothing goes to waste.
Wash the remaining rocks as best you can – they can never be clean enough for this stage. By washing them clean you will protect your polish barrel (if you have a dedicated one) from getting the odd bit of grit in over different batches and it will last longer giving you the confidence to use it on seriously difficult types of rock down the line – such as obsidian.
Place the selected rocks in the barrel as usual and add lots of plastic pellets. As you add them, shake the barrel a bit to let them sink in and fill all the spaces. Then add more until they are level with the top of the stones.
Then place 1 roughly heaped tablespoon of cerium oxide or aluminium oxide into the mix per pound and a half of rock. Again, this is not an exact science – be sparing rather than over enthusiastic though as the polish can be fairly expensive.
Add water to the mixture until it reaches the tops of the rocks then fasten the lid on.
The absolute LESS amount of time the barrel is turning at this stage the better, because the longer it rotates, the more chips and pits will occur on the surface of the rocks. For this reason, we suggest checking the barrel every day or so after the first 4 days. You will get used to which types of rock take a polish quicker than others – Amethyst for example shines up really quite quickly, whereas Obsidian can be a pain!