The two-part Post “What Do I Need to Start Tumble Polishing Stones Myself? And What Will It Cost Me?” was originally done by me three years ago in April 2018. However, prices have changed since then, as have the grades of grits and polish that are stocked by my supplier. The Covid-19 pandemic has also disrupted international trade and shipping. So I updated the original Post, setting out the main changes in light green. The edited Post is here.
My supplier is the Rotorua Lapidary Rock and Mineral Supplies Ltd. I bought my first tumbler and grit etc. from them and find that they provide excellent service and very fast dispatch. Other people have supported this view. If their website shows they are out of something, it’s worth contacting them by phone or email as they may simply not have listed it yet or need to re-package it from bulk supplies.
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. All my Posts about my own tumble polishing on this Blog reflected the use of these five “stages”. Now, however, Rotorua Lapidary stock 80/100, 220 and 400 silicon carbide grit and only one grade of tin oxide recommended for tumble polishing called “Tumble Polish” (they also have a very expensive “Pure Tin Oxide”). In response to my inquiries in November 2020 about these changes, Colin Simmons advised me:
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 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.
I still have stocks of everything except 320 grit so I am now using the 400 grit instead. I am still using both pre and pro-polish and will probably do so until they run out. I may try skipping the pre-polish as an experiment, but have yet to do so.
Note: You may wonder about the difference between “80/100” and “100” silicon carbide grit. As Rocktumbler.com notes, the grit size relates to the size of the particles of grit, with grit size 80 being 250 microns, size 100 being 149 microns, size 220 being 68 microns, size 325 being 44 microns, size 400 being 37 microns and size 600 being 20 microns. A “micron” is 1/1,000,000th of a meter, or 1/1000th of a millimeter. So a particle of 60 grit being 250 microns across is about 250/1000th or 1/4 millimeter across. Ungraded grits, or grits within a grade range, do not require the same level of processing needed for specifically graded grits. That allows such grits to be sold for a lower price than graded grits. Silicon carbide sold as “80/100″grit would have a range of particle sizes smaller than 80 grit (250 microns) but larger than 100 grit (149 microns).
Great information, thanks John. Maybe one day I will get into polishing stones … I was talking to a friend the other day about Orepuki’s gemstones and she asked how to go about polishing. I said I didn’t know, but did know someone who did. So I am going to pass on your info. to her. She said that she’s not ready yet, but looking into doing it once retired. A great retirement project! If I wasn’t writing, I’d be in like Flynn!
Thanks for your Comment, Kay. Please do keep writing! Best wishes.