There are many different ways to dop a stone- some use shellac, some use superglue. Some, such as I, use green dopping wax. I got the above dopping station from Kingsley North. They provide me with much of my equipment and tools (http://www.kingsleynorth.com) and their customer service is top notch. This dopping station simply plugs in and the copper pot heats up the wax. In addition, there's room on top to place rocks- more on that in a minute....
The above pic shows my dopping sticks- these are wood dowels that I've cut into approximately 6" lengths to house the wax. Some use metal dops, and there are other materials available, but these are cheap and easy for my purposes. The smallest stones can be dopped on a strong piece of steel wire, but honestly, I don't work that small!
My dop sticks range from about 3/16" to 5/8" in diameter, but really I have a good range of sizes just in case I need them. The important thing to remember is that the diameter needs to support the size of the stone. I like my dops to be about half the diameter of the stone being set.
Before I even dop the stones, I do a lot of work preparing them: first, I grind down the bottom to flat and grind the sides into whatever shape I need/want. I make sure I have enough vertical stone surface on the sides- minimum of 1/8"- and then I make sure the sides all meet up nicely. Next, I use 2 more wheels to grind, refine and polish to a matte sheen the bottom and sides of the stone. I also always put a slight bevel on the bottom of the stone for ease in setting. Now I'm ready to plug in the dopping station!
Above is the dopping station heated up most of the way, with 3 sticks 'soaking' and 3 stones heating up. It's really important to heat the stones up, or the dopping wax will not stick to them. I've heated up all kind of rocks and never had a problem- even opals and turquoise. Soaking the sticks helps to melt the dopping wax that was melted on there before.
I also like to mix up the wax in order to evenly distribute the heat. Plus, it's fun.
Once it's nice and melty, put a thick coating of wax on the stick, with enough so that the wax has the ability to sink down to the bottom of the stick and flow a bit to cover the stone. This will come with experience. Don't wait too long to stick it to the stone, or it will cool too much and not stick.
Your goal is to keep your fingers wet, but not too wet- so that you can form the hot wax to the base of the stone. I tend to use my tongue juice (aka spit) but you can also dip your fingers into a cup of water. If your fingers are too dry, the wax will stick to your skin and you will say ouch, or words that express that. You don't want your fingers dripping with water, though, so be conservative.
Once cooled a bit, the wax will cease to flow and will keep its shape. Your goal is to match the outline of the stone with wax; in a sense, you are creating a buttressed structure of wax that gradually tapers down from the stone to the wood dowel. This helps to reduce stress on the stone as you push, grind and polish it. You want it to be fully supported or the stone may crack or come off the dop while you are working.
Here are the 3 stones dopped and hanging out, cooling. I cool them upside down, and if in forming the wax, some drips down the sides a bit, it's okay as long as it's not more than about 1/8" down, which is where my bezel wall will meet the curved part of the stone. If it covers up any more of the side of the stone, it will make forming the top of the stone difficult until it is removed. With hot flowing wax, it can be a challenge to control it when all that is between you and a burn is spit. Flow happens!
So now you are ready to rock and roll!
IF, by chance (of course), your rock should go flying off the dop, don't despair. Of course you have your safety goggles on and you are protected! Yesterday I polished 8 rocks and one popped off the dop at the last polishing step. It happens with all that pushing, forcing and grinding.
What you will be left with is a nice flat surface on your dop that closely matches the outer shape of your stone. Dry off the dop and the stone completely.
What I've found to be successful is to cover the flat dop surface with 2 layers of red double-sided tape. I simply fold down the areas of tape that run off the edge of the dop surface. This provides a nice cushiony surface, and your stone will very much enjoy sitting on it's new perch. Pushing down and completing your polishing will reinforce the bond. Of course, the use of water when grinding/polishing will serve to weaken the bond eventually, but hopefully you'll be pretty much done before the stone starts slipping around on the tape. It's a pretty decent fix for losing a stone off the dopping wax.
I like the red liner tape because it's got some thickness to it; some sponginess is good and creates a better bond.
Getting the stones off the sticky tape is just a matter of firm pulling up- make sure you don't stress a thin area of stone while you're pulling up on it, or it may crack.
To remove the stones from the wax dops, put them in the freezer for 5 minutes. The wax by then will contract and the stones will pull right off. The freezer won't damage the stones. I once forgot about some dops in the freezer for about 3 months, and the stones came out unscathed!