Cut and Polish

While a good eye is needed to select a nice piece of rough, talent and artistry are required to produce a finished cabochon suitable for adornment. This is where the lapidary’s skill really shines. It is also the most fun. Taking a dull piece of rock and turning it into a shiny thing of beauty is very satisfying. There are many different ways this can be achieved. However, they all involve grinding and polishing.

As a child, this author would sit for hours, rubbing a pretty rock back and forth on the concrete walkway in the backyard of her family home. Well, it probably only seemed like hours. Now she has a much faster and easier way of achieving a polished stone.

As mentioned before, it all boils down to grinding on the pre-trimmed slab and then polishing it. The methods are as varied as are the lapidaries themselves. But they all begin with a coarse grit and work their way to finer and finer grits.

Some lapidaries prefer to use sanding/grinding belts. These are impregnated with silicon carbide. For the most part, these belts are mounted to a wheel that is turned by a motor. Water is supplied, either as a drip or in a reservoir, as a coolant and lubricant.

Others will use a combination of solid silicon carbide wheels and belts. A drawback to the solid silicon carbide wheels is that, if you are not careful to move the cabochon around on the grinding surface, you will get dips in the wheel and these must be ground out (or dressed) periodically. A diamond T-bar dressing tool is required for this. Even if you are careful, periodic dressing is required. The belts wear out quickly and must be replaced quite often. However, some lapidaries consider this to be the most economical.

This author prefers to use a machine fitted with diamond impregnated wheels. The initial cost is greater, but they last much longer and never need to be dressed. She has tried the method mentioned above and finds that diamond cuts faster and requires less water, which is much less messy.

Some lapidaries prefer to use “laps”. These are flat discs, the best of which are diamond. They spin around as would an old-fashioned long playing vinyl record. These laps are mostly used by lapidaries who facet gemstones, but some “cabbers” find them easier to use.

All the preparation, selecting the rough material, cutting it into a slab, trimming it to the rough shape and selecting your method of grinding and polishing, all lead up to the moment when the lapidary gets in front of their grinding/polishing machine and starts to cut the stone. For this author, this is the most anticipated moment.

Her grinding/polishing machine has six wheels. The coarsest wheel is used to refine the pre-trimmed shape and remove the deepest scratches. The next wheel is used to further refine the shape and start to remove more of the scratches. The first two wheels are hard wheels; there is no give to them. The third wheel is a little resilient and generally more pressure is applied to this and the subsequent wheels.

Sufficient time must be spent at each stage to remove the scratches. The whole point of moving from coarse to fine grit, is to move from big scratches to very small scratches and finally to no scratches. The cabochon should be dried and inspected before moving on to the next wheel. If you do not spend enough time at each stage, it is a waste of your time. You will get to the end and still have visible scratches on your cabochon. Then you must determine how bad the scratches are and back track the appropriate number of steps.

Some materials will naturally take a better shine than others. So some lapidaries will finish up with a polishing compound applied to a buffing wheel. This author uses a hard felt buffing wheel first, and then a soft muslin buff. Any buffing compound residue must be washed away.

It is very exciting to come to the end of all this, dry your cabochon, and look at it in the sunlight. If you have done everything right, you will have taken a dull piece of rock, with pale colors, and turned it into a vibrant and shiny work of art.

Occasionally, this author will have visitors to her studio. Some will ask if they might try grinding and polishing a stone. Their delight at the process and happiness with the result is always a source of great joy for her.

By: Dianne Lehmann

About the Author:

http://www.syzygyjewelry.com