|The following is a simplified explanation of how to polish a gemstone.
Very simply put, polishing is the systematically progressive reduction in the size of scratches until they are invisible to the naked eye. As one grinds upon a stone with diamond tools, the diamond crystals in the bur are making grooves in the stone as it removes material. On a microscopic level, the act of each diamond crystal plowing through the stone produces an incredible amount of point contact heat. This will cause crazing of the stone much like suddenly heating a very cold dish in one small spot. The larger the diamond crystal, the more material is removed, thus more heat being produced, thus more and deeper crazing of the gemstone. Here is one of the reasons you should always use a water bath while grinding, to keep the heat and crazing to a minimum. To achieve a superior polish, all of these small crazes must be completely removed.
So, while it can be very satisfying to rapidly remove material with large grit burs, you must progressively reduce the grit size in your burs as your carving takes shape. Thus each smaller grit size bur must remove all of the scratches and crazes from each earlier, larger grit sizes. When you have reduced everything to the 325 or 600 grit level in burs, you are ready to progress to the diamond paste polishes.
When transitioning from diamond burs to the diamond pastes, the attention spent on this transition will reflect on the success and quality of your final polish. Time spent at this point will make all the successive polishing steps easier and faster. When finishing up with the burs, the gem contours will have little bumps and flats left by the bur. Even with extreme care and attention to this detail, there will be some of this surface irregularity. So when you first start with the larger grit diamond polishes, like the 240 or 325, it is very important to work until the surface has a smooth uniform curvature with no bumps or flats. This first step is one of the keys to a superior polish. Any bumps or faceting left at this step will be highly visible when you finish the polishing process. So you will be spending the same amount of time and effort as you would with the superior stone but the final polish will only be ho-hum. Comparing the two stones, you may not know why, but you will see that one will be superior to the other. Your subconscious mind will note the 'wobbling' of the light reflecting from the uneven surface. When the curvature is very uniform and even, the reflecting light will be steady and uniform.
With the diamond paste polishes, you will not get the subsurface crazing so much but you will get a uniform scratching corresponding to the size grit you are using. Each successive grit size must remove all of the previous size scratches. If you do not remove every scratch from the previous grit size, the successive steps will be using smaller grit sizes, and they will never remove those larger scratches later on. So when you are in the final polishing steps, any previous scratches will stand out and the final polish will seem cloudy or patchy. This in a nutshell, is the act of polishing.
Your polishing kit contains some of the basic tools needed to polish. Every carver will have tools and points they refer but this is a basic tool kit. Leather wheels, felt points, bristle brushes and the corresponding mandrels. To set up your kit, get some freezer zip lock baggies (tougher) and place each tube of diamond polish in its own baggie. Take the leather wheels and place them on the mandrels, insert them into your hand piece, and true them up with a file until they run without any wobble or bumping. (Use a dust collector!!) After this step, take a knife or cut-off disc and place slots across the edge. These slots will hold onto the paste and help the polishing action. Place one in each baggie of the 240, 325, 600, and 1200 polish. Now in each baggie, place a single bristle brush, porte polisher (end brush), and felt point with a screw tip mandrel. Now you have your polish kit set up and ready for polishing.
Be very careful about cross contamination of the different grits. After using each grit, place all tools & items in the corresponding baggie and clean up the area and wash the stone so you won't contaminate the next step. A single 325-grit diamond crystal finding its way into the 2000 polish baggie could put nasty scratches on your almost completed piece. This can really ruin your day.
Some stones will like leather but not felt, some will like felt but not leather. On some stones you will find that you have through go to each successive step of grit and with some stones you can skip some steps. This is the individual characteristic of each type of stone and it is a learning process. You will find that certain steps work best with some stone but not others. There are several books written on gemstone polishing and this will help you with your process. We sell the Henry Hunt books and they are excellent at explaining which techniques will work with which stones.
Have fun and create your own gemstone carving. If you have questions, call or e-mail for help.