A Series of Posts called “The Seven Stages in Tumble Polishing Stones” was begun in November 2017. It went through, step-by-step, the seven stages of how I polish stones using a tumbler and 4lb barrel. A set of 40 beach stones collected from Riverton were used to illustrate each stage. The first Post in the Series is here, while a summary can be found as #2 in “Six Past TumbleStone Posts of Interest to Beginning Tumble Polishers”. However, changes in the grits and polish supplied by the Rotorua Lapidary Rock and Mineral Store in late 2020 mean that now only six stages are required instead of seven, and a couple of other minor changes have occurred.
About six months ago, Rotorua Lapidary changed the silicon carbide grit and tin oxide polish that they stock. Before that, they stocked 100, 220 and 320 grit along with pre-polish and pro-polish tin oxide powder. Now, however, the store stocks 80/100, 220 and 400 silicon carbide grit and only one grade of tin oxide recommended for tumble polishing (called “Tumble Polish”). So there are three main changes. First, the coarse grit size 100 grit has been replaced by 80/100, which means the latter contains a slightly wider size range, the overall effect being that it is slightly coarser. To all intents and purposes, this is not a significant change (though it will make the price lower). The second main change is that 320 grit has been replaced with a finer 400 grit. I asked Rotorua Lapidary by email why this change was made and they replied: We have a new supplier and they don’t stock 320 grit, 400 grit is finer therefore beneficial when working towards the polishing process. The third main change is that two grades of tin oxide polish powder have been replaced with one polish powder. In response to my inquiry about this change, Rotorua Lapidary stated: The new supplier has a one step polishing product which we trialled very successfully, and have every confidence in supplying the market... The tumble polish is still the same type of polish as the pre and pro polish only it is slightly finer in micron – with using 400 grit (which is finer) instead of 320 grit you can eliminate the pre polish process. So the main effects of the second and third changes are to reduce the number of stages required by one, along with a small reduction in the overall costs.
My original seven stages in tumble polished stones were: Stage One = Stone collection (not usually included in accounts of tumble polishing). Stage Two = About a week in 100 mesh silicon carbide grit followed by a soap wash for a few hours. Stage Three = One week in 220 mesh silicon carbide grit followed by a soap wash. Stage Four = 320 silicon carbide grit followed by a soap wash. Stage Five = Tumbling in a tin oxide “Pre-Polish” powder (five microns in size) for three to five days, followed again by a few hours soap tumble. Stage Six = The “Pro-Polish” tumble, using tin oxide powder of one micron size, for at least one week. Stage Seven = A “burnishing” tumble for a week in borax.
My up-dated stages are now reduced to six, as follows: Stage One = Stone collection. Stage Two = About a week in 80/100 mesh silicon carbide grit followed by a soap wash for a few hours. Stage Three = One week in 220 mesh silicon carbide grit followed by a soap wash. Stage Four = 400 silicon carbide grit followed by a soap wash. Stage Five = Tumbling in “tumble polish” powder for at least one week. Stage Six = A “burnishing” tumble for between two and seven days in borax. See the Summary Table below.
Summary Table
| STAGE | ORIGINAL SEVEN | UP-DATED SIX |
| ONE | Stone Collection | Stone Collection |
| TWO | 100 grit, 7+ days | 80/100 grit, 7+ days |
| THREE | 220 grit, 7+ days | 220 grit, 7+ days |
| FOUR | 320 grit, 7+ days | 400 grit, 7+ days |
| FIVE | Pre-polish, 3-5 days | Tumble Polish, 7+ days |
| SIX | Pro-polish, 7+ days | Burnishing, 2-7 days |
| SEVEN | Burnishing, 7 days |
Currently I am using 400 grit for tumble polishing (as I ran out of 320 grit) but as I still have some stocks of pre-polish and pro-polish powder I have not yet moved to the six-stage process.
Note that different people have developed different stages for tumble polishing which use different grit sizes etc. What is common to them all is the use of a coarse grit first (provided it is needed – smooth beach stones can be started with a finer grit), followed by a medium-to-fine grit, then a pre-polish stage using very fine grit or a pre-polish powder, then finally the polish stage. See, for example, the Gold Rush Trading Post’s stages and those of Mama’s Minerals.
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