Grit to Polish Ratios: How much grit to use?
Think there are no controversies in the grit world. Well there are and they are fairly intense.
The most puzzling one is about the suggested amount of grit two use. The two largest tumbler manufacturers in the US disagree 100 % about how much grit to use in the standard four step tumbling process. For the pre-polish and polish steps one suggests a ratio of half the amount of media as is used in the Coarse and Medium grinding steps. For instance if per item grit use is two tablespoons of grit for every pound of rock then one would use one tablespoon of pre-polish and polish. That's a big difference from the other manufacturer who suggests an even ratio. One for One.
Which is correct? Our research across dozens of great tumbling professionals is that the common usage is 2:1. Of course tumbling has as much randomness in processing as anything so you always want to keep in mind any adjustments. Results are the key. If you get better results with more pre and polish then make your own rules.