cabmaking4

How To Make a Cabochon, page 4
by Paul W. Cinnamon

#8:     DOPPING THE CAB
     The next step is to place the cab on a dop stick for ease of handling. Dopping isn't absolutely required, and with experience there may be times when you will prefer to hold the stone with your fingers throughout the cutting and polishing process. I frequently work opal in this manner. If I am concerned about heat damaging the cab, you can use double-sided carpet tape to hold the stone on the dop, but most of the time, you will find securing the stone with dop wax will make it much easier to work.
     A note about dop pots. I now use a commercially manufactured unit, but for several years I used a light bulb with a small shallow tin can suspended above it holding the dop wax. Most of the commercial dop pots are nothing more than a can housing a 60 watt light bulb that is used to heat the wax container.
     There are several different dopping waxes made for different situations in cabbing and faceting. I use green dop wax for cabbing, because it's cheap and readily available at almost all rock shops and lapidary supply companies. A couple dollars will probably purchase enough wax to supply you for most of your life because you can use the same wax over and over again.
     There may come a time when you may wish to dop a very small stone and will find the bulk of the dop wax to be a problem. For these situations I recommend the same two-part epoxy that I use when dopping stones for faceting. It is made by Vigor, and is named 5-Minute Jewelers Epoxy. It's inexpensive, I believe the last I purchased from the local supply house was $2.99, and will supply you with enough to last for years if you take care in keeping the caps on the tubes, but not too tight. Eventually, I usually ruin a tube before it's depleted by screwing one of the caps on so tight that it splits. I keep the epoxy tubes upright in a small jelly jar that is about 2/3 as tall as the tubes. Whenever the epoxy temperature is less than about 80 degrees, I run the jelly jar almost full of hot water and let the epoxy warm up for a few minutes before I open the tubes, because cold epoxy doesn't flow very well.
     I always use a metal dop when I secure a cab with epoxy, because I use heat to remove it from the dop. To do this without worrying about heat damage to the cab, or burning your fingers, place a wooden clothespin on the dop stick toward the end away from the cab. Cut a thin strip of chamois from one used to clean your car or window glass. Cut it about 1/8 inch wide and 6 or 8 inches in length. Wet this with water, and wrap it securely around the cab leaving only the epoxy joint exposed. Apply heat to the dop stick about an inch back from the cab, using an alcohol lamp, small torch, or even a candle. As soon as sufficient heat radiates down the dop stick the epoxy will release. While the epoxy is still warm, it can be easily scraped from the back of the cab with a knife blade.
     For dop sticks there is almost no end to what you may use. I use dops made from many things, depending upon the size of the cab being cut and what I may have available at the moment. For a few dollars you can purchase ready-made dop sticks. Some are made of aluminum or copper tubing that has been flared at one end. If you have a plumber's copper pipe cutter and flaring tool set, you can make these yourself. You can also cut pieces of wood dowel rod in whatever diameter and length you desire. I frequently use regular carpentry nails, especially those with a perfectly flat surface on the head. For very small cabs, I sometimes use finish nails. Experience will probably dictate the length you prefer, but for general work a length of 3 to 4 inches works best for me. My main consideration in selecting a dop is one that will set upright on a flat surface at a 90-degree angle.
     To secure the cab to the dop stick, turn on the dop pot and place the cab face side down on the dop pot, in an area somewhat away from the source of the heat, but where it will be gradually heated. When the wax in the pot begins to melt, turn the cab over and move it closer to the heat element. Hold the dop stick suspended with one end in the warm wax until the wax adheres to the stick. Turn the cab over so that the backside is up, and place the dop stick with the soft wax adhering to it in the center. Carefully lift the dop stick with the cab attached from the dop pot, and place it on a flat dry surface. I try to place in a spot where I have a vertical object in the background to use as a guide to make sure the dop handle is at or near a 90-degree angle to the cab. Quickly center the dop stick, and carefully using your fingers, press and smooth the hot wax around the dop stick making sure the cab is hot enough that the wax is bonding between the cab and dop. By the time you have accomplished this, the cab usually has cooled enough that you can either dampen your fingers and quickly cool the wax, or carefully lift the cab by the dop stick and place it in cool water, which will quickly cool and harden the wax. You can now lift the cab and recheck your centering and leveling by rotating the dop while observing the cab. If you are satisfied with your work, you are now ready to begin beveling and doming the top of the cab.
     You will start your cab using a coarse grit lap, usually in the range of 80 to 120. After being sure that you have an adequate supply of water, start your machine.