Sanding and Polishing Tips for Opal

All opals on our Diverse Opals website are sanded dry with silicon carbide paper. I know many cutters believe that wet sanding with a range of soft diamond wheels is the best method. However, both wet sanding and dry sanding have their advantages and disadvantages. I will tell you what I like and don’t like about dry sanding. Dry sanding is cheap. I can determine quickly where the scratches are because it is dry. I only use 2 grades #240 and #600. I don’t like the dust but I do use a dust extractor and dust mask.

I consider sanding and polishing to be the 2 most important stages in processing a piece of opal from its rough state to its completion. With maybe more importance placed upon the sanding.

The machine I use for sanding is a GMF dental lathe. I like this machine because it has 2 speeds, 1500 and 3000 rpm. For the majority of my work I use 3000 rpm. Occasionally I use 1500 rpm for sanding optical glass on free form opal triplets.

If you don’t have access to a dental lathe you might be able to modify a 6” or 4” metal grinder.

Please Note. Always take care when using any machines. Always wear protective apparel.

The disc on my dental lathe was specially made for my machine. It is made from aluminium and is 4 ½” in diameter. This diameter allows me to cut 4 discs from a standard 11” x 9” sheet of paper.

I use ¼” neoprene as backing for the paper. The paper is fastened with an adhesive that will not set hard. I use disc cement. Any adhesive that allows the paper to peel easily will be suitable.

The brand of abrasive paper I use and sell is Matador. I have found this paper to be one of the most uniformly graded papers I have ever used. I keep grades from #80 – #5000 grit silicon carbide.

One machine I use for polishing is a Gemmasta GSP8. It has an 8” leather buff attached.

The majority of polishing is done on chrome split leather even though I do use felt on some carvings, boulder and stones where the surface is hard to access.

The leather buff works best at a slow speed. About 800 rpm is sufficient.

I use and sell a high purity cerium oxide called O-pol. When used in conjunction with a good quality paper, the polish on opal is achieved very quickly. Best results are achieved when the surface of the leather starts to dry.

If you have any questions I will do my best to answer them.