The Eclectic Lapidary - Introduction to Cabochon Cutting and the Lapidary Hobby (continued)

Volume I, Number 4	Carol J. Bova, Editor. Web Publishing by Doppler FX.	03/01/97

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Introduction to Cabochon Cutting and the Lapidary Hobby (continued)

by Dick Friesen

Sanding and Polishing

Step 10: Sand on 280 Grit
Step 11: Sand on 600 Grit
Setp 12: Sand on 1200 Grit
Setp 13: Pre-Polish on 14000 Grit
These sanding steps are for the Diamond Pacific Titan and Genie and will be slightly different for other brands.

(On the silicon carbide Drums the Grits are: 220, 400, and 600)

Sanding

Sanding is the easiest to describe and the hardest to do of all the steps in making a cab. It is also the most important of the steps. Just progress from the coarse grit to the finer grits. At each grit, remove all the scratches from the previous step. Clean the cab between each of the silicon carbide belts. It sounds so easy but silicon carbide belts wear relatively fast and a worn 220 grit may be smoother than a new 600 grit. With the finer grits you may need a magnifying glass and a dry stone to see if you have removed all of the previous scratches. Diamond is easier to see the scratch removal, a worn diamond does not get finer just slower. With any belt you may find it easier to remove all the previous scratches if the last step on each belt is to sand in only one direction. Then when you are looking for scratches any that are going in that direction are scratches that have not yet been removed and you are not yet ready to go on to the next belt. Silicon carbide has another characteristic that can irritate you. The grit can come loose from a worn belt leaving a deep scratch in the cab that may require going back to a coarser belt to remove.

Pre-polish

Finish sanding on the 14000 grit diamond wheel. A well worn 600 silicon carbide is about a 1000 grit and will pre-polish adequately.

Step 14: Polishing the Cab

Cerium Oxide
Cerium oxide is the polish of choice for agate and most other stones of agates hardness. Shake container and spray a little cerium oxide on its leather buff (do not mix polishes on the buffs) and hold the cab against the buff using a tight grip on the dop stick and a fair amount of pressure. The cab should "pull" against the buff as the polish dries and polishing takes place. Spray more oxide as the buff dries. The agate will get warm in the polishing process, be careful not to let it get hot enough to melt the do wax. Agate should polish in one or two minutes.

Other Polishes

Tin Oxide
Used the same way as cerium oxide but works better on softer stones (opal, turquoise, obsidian, etc.).

Diamond
Comes in three forms, belts, paste and sprays. 3M makes a 3,000 and 50,000 belt set that is excellent for jade or any stone that has a tendency to undercut. Paste and sprays are cheaper but are harder to work with.

ZAM
Used on a canvas wheel, Zam is used on soft stones like lower grade turquoise and plastics (reconstructed stones).

Chrome Oxide
Mixed with vinegar, chrome oxide is preferred by many as a polish for jade.

Aluminum Oxide
Sold under trade names like Linde A, or Linde B, it is used on harder stones such as sapphire, but also good for agate.

Others
There are several other polishes sold under various trade names and many people swear by them, others at them. After you are familiar with the standards feel free to experiment. You may find one that works better for you.

Remove from Dop Stick

Refrigerate
If a freezer is available, remove the cab from the dop stick by placing them in the freezer for a short time. When they are frozen the cab will almost fall off the stick. Ice cubes in water will also work.

Heat or Knife
If a freezer is not available the wax can be heated over the burner until the wax is soft enough to allow the cab to be pried off. Any remaining wax can be removed with a knife. The dop wax may also do dissolved with alcohol.

Dick Friesen writes, "I have been cutting cabs both as a hobby and as a commercial cutter for about 25 years. I teach lapidary for our local Gem and Mineral club and for our local recreation department. I also do lost wax casting to keep my sanity when all else fails. I am retired from Lawerence Livermore National Laboratory where I ran one of their larger Physics ADP systems and did network design."

Next Month: Stone setting, lapidary materials, and other forms of lapidary activities.