Stone dopping done fast and right
by istván.
2023. május 3.
There are a lot of truly dumb guides about gemstone dopping, and it’s such a fundamental skill of our field that it is worth learning to do it the right way. What I teach as "the right way" is also the cheapest way, most flexible way, fastest way, and requires the most reusable and least specialized hardware.
So throw our your stupid dop pot and wooden sticks and learn to dop like a professional.
For those unfamiliar (why are you reading this?), dopping is how one attaches a stone to some kind of stick (a dop) to allow you to exert more precise control over it during the cutting process. For 3,570 years, this has been done using a combination of seal wax and shellac.
For the last four decades, Internet "experts" have advocated for everything from hot glue to Elmer’s, to gorilla glue encased in nail polish, and even steel-bearing epoxy. In the worst extreme, lapidary hobbyists love pushing stones up against the wheel with their bare hands. This eats your fingernails, gives you a false sense of control, and over time destroys your nerves and joints until you can no longer grip things like the 75-year-old at your local rock shop who can't hang onto the coins when making change.
Please don't listen to the "experts" and amateurs.
Hot glue flexes, which destroys your ability to control the stone, which was the whole point of dopping.
Elmer's glue dissolves in water. This is bad because you are cutting in a wet environment with a constant water feed.
Super glue can’t handle the force and your stone will easily pop off. It also leaves behind a residue that has to be dissolved off in acetone, which is absorbed through the skin for permanent storage in your kidneys, or burnt off into cancerous gas.
Epoxy is the worst of all worlds and the form advocated by all many “master cutters.” It only breaks down under methylene chloride, burns into an incredibly cancerous gas that smells like roasted peanuts, and flexes just enough to ruin microfacets because it needs to hold up against torsion in its intended industrial use.
Your health is worth more than that even if you don't think your stones are. Use wax.
Wax is reusable. Wax is cheap. Wax is fast. Wax won't flex or ruin your precision. And wax won’t kill you.
If a stone ever does fall out you have an exact imprint of how it was sitting so you can just warm it up and keep going. You can actually inspect your work along the way and check how much weight you are losing at each step.
Boyd Fox had an awesome video teaching his way of wax dopping, which is very similar to how I do it.
Hobby cutters will rage and cry that this only works for sapphires and not anything heat sensitive or valuable. That is bullshit and user error. I trust this method daily with precious opal ($5,000+), which everyone claims is so heat sensitive and delicate: I’ve never damaged a stone this way.
If you are interested in learning, I suggest buying a bag of cheap apatite crystal rough (not cabochon material) and practicing attaching and removing it from your dop until you can do it without cracking an apatite or expanding any existing cracks.
Wax flows and bonds when the wax, the stick, and the stone all reach 150 F. The apatite will fracture around 170 F and crumble by 200 F. There is so little room for error (e.g. getting the stick too hot so it transfers too much heat through the wax and into the stone) that if you can do it with apatite you can confidently do it with anything else.
You can start with Mr. Fox's very conservative and safe approach using an alcohol lamp, and when you have mastered that, move up to using a butane torch.
My method involves heading the brass dop with the torch until it has enough heat to melt the wax, and then placing the stone and holding my finger on it to monitor the temperture. Assuming everything feels good, I quickly run the torch back and forth around the base of the stone to warm it. If done correctly, the wax flows perfectly over the stone to create a very secure bond.
To release, warm the dop with the torch for 3-4 seconds and pull the stone free. Set the dop aside and warm the stone in an alcohol lamp using Mr. Fox's technique to remove any residual wax.
I have dopped hundred of stones with this technique, and I use the same process for faceting precious gem rough and forming cabochons. For cabochon work, you can buy a length of brass rod stock at the hardware store and cut it apart to make cheap brass cab dops. If you need them flat, just machine them in a $25 Amazon.com mini lathe.