By Merrill O. Murphy

Iíve checked the questions most asked the last several months during New Mexico Faceters Guild meetings. For a lesser time, I have been monitoring the questions posed by e-mail from the on-line Facetersí Digest. The most frequently asked question is: how do I dop and transfer my stones quickly and easily?

Every facetor will have his favorite method, and that is as it should be. Still, every facetor should be able to use all the better-known dopping and transfer methods. There are good reasons for this. Some gem minerals are downright fussy about their tolerance, or intolerance, to heat. Others are fragile or may have a tendency to cleave in any direction. A very few are attacked by solvents. One, salt (HCl), dissolves in water. If faceters have a hankering to facet a great many minerals, then they should be adept at handling all available dopping agents.

Actually, there is no great number of commonly used dopping agents. Letís see... there is dopping wax that melts at several temperatures and identified by color. There are stick shellacs, the cyanoacrylates (Super Glues in several forms), and the epoxies with several their setting times and bonding strengths. Thatís about it. I have found it useful to sometimes use two dopping agents to effectively dop one stone.

Now, let us see how to choose a dopping agent and how to properly use it. If you are cutting quartz, beryl, and topaz, stones that are neither particularly heat sensitive nor eight or greater in hardness, then I suggest wax, or shellac, or even both. Why? Because they are quick to apply, have adequate strength, and are both quick and easy to release from the dop. However, I know from experience that many faceters have trouble with wax. The problems with wax are heat and cleanliness. Before using ANY dopping agent, clean the stone and the dop thoroughly with alcohol.

Dopping With Wax And/or Shellac

Wax dopping evolved as a way of attaching a handle to stones being cut as cabochons. All kinds of ways were used to heat the wax and the stone. Early in the game, cutters heated wax in a pot held above a candle flame, and later Bunsen burners. The stone was heated above the same flame but on a small, isolated sheet of metal. The dop, made of wood doweling, required no heating. Hot wax was smeared on the dop end then pressed against the hot stone. While cooling, the wax set up and locked the dop in place.

Later, a torch was sometimes used to heat wax and stone. Some cutters used an electric hotplate. I have often used our gas-fired kitchen range. The stone was heated by placing it above the pilot light. The wax stick was heated above the burner flame and dabbed on the dop stick. The wax on the stick was then smoothed with wetted fingers, heated again over the flame, and pressed against the heated stone. Since dopping for faceting requires more precision and involves metal dops, slightly more sophisticated methods are required.
Make yourself a wax-dopping platform. On your workbench, set two bricks a few inches apart. Place a metal pie pan to span the opening between bricks. Thatís it. You then place your stone in the pie pan and heat the pan with a gas torch applied to the underside of the pan. Some stones can stand direct torch heating, but a flame always leaves a thin layer of residue on the stone that weakens the wax bond. We need no weakened bonds during dopping.

The metal dop must be heated using the flame applied to its midsection. Since it becomes uncomfortably hot to hold, we then need a dop handle. Make one by drilling a 1/4-inch hole an inch or so deep lengthwise of a piece of wooden dowel.

Use a medium-grit disc to grind a flat where the table will be on your stone. Heat the stone on the platform until a tiny flake of dop wax, placed on the stone, turns shiny. Place the chosen dop into the dop handle and play the gas flame on its mid-section until a flake of the wax melts on the dop. Next, heat the end of the wax stick in the flame and rub some of it on the hot dop. Press the waxed dop against the ground spot on the stone and invert the dop to leave the stone on top. Hold it all in that position until the wax sets.
At this point, I like to lock the dopped stone in the transfer jig with a flat dop in the opposing position. Press the dops together until the stone and opposing dop meet, then heat both dops until the wax again becomes shiny. Let the joint cool to room temperature before faceting. Note: The above sounds a bit confusing upon rereading. We are not attaching the opposing dop at this time, merely using it to apply pressure to have a minimum of wax between the attached dop and stone.

How much wax should be used? You will learn quickly by practice. You need enough to completely cover the meeting surfaces of dop and stone, plus a tiny rim outside the joint. The tendency, however, is to use too much wax. With too much wax, one invariably finds himself cutting as much wax as stone in the girdle area. Wax can also foul a lap.

Stick shellac (available at lumber and hardware stores) can be used in exactly the same way as for wax. The Graves company recommended shellac dopping, probably, because the melting temperature was slightly higher. I highly recommend its use with wax if your stone is somewhat heat sensitive, like transparent red Mexican opal for example. Dip the end of the shellac stick in alcohol and rub the wetted area against the dop point on the stone. Repeat this two or three times. Use wax, as described above, to dop to the shellacked area, BUT WITHOUT HEATING THE STONE. The hot wax will adhere to the cool shellac surface. If your gemstone is small, you may wish to apply a light band of cyanoacrylate (Super Glue) at the wax/stone interface to increase the bond strength.

Cyanoacrylate (Super Glue) Initial Dopping

A number of the cyanoacrylate cements would seem ideal for dopping, but, like wax, there are drawbacks. When using cyanoacrylates, a flat should be fine ground at the future location of the table facet. The cyanoacrylates bond best to a clean, smooth surface, and a minimum of glue should be used. Place a tiny glob of the glue on the stone or dop and press the two together. Hold for about 20 seconds before mounting the dopped stone in the faceting machine. Wait ten minutes before beginning the cutting process.
There are several cautions to be observed when using cyanoacrylates:

Be very careful to avoid getting the stuff on your fingers. It can bond fingers together so tightly that a surgeon is required to free them.

Always use a minimum amount of the Super Glue. It is difficult to get too little.
Be aware that the Super Glues may lose bonding strength with age. If it does not stick well, then get a new tube.

All cyanoacrylates are not equal. Experiment until you find a brand that suits your purpose and stick with that brand. I like one called BONDINI EVERYTHING GEL. The gels make getting a minimum amount a little easier.

Here is a neat trick faceters sometimes use. Heat your stone on the dopping platform and apply hot dopping wax to the stone. Take the stone in gloved fingers and press an unheated dop hard against the waxed area. Hold until the wax solidifies and then lift the dop off. It will not bond to the wax, but an exact impression of the dop end will be left in the hardened wax. Now, place a little cyanoacrylate glue on the dop end and press it into the wax impression. Cyanoacrylates will bond readily to dopping wax. During later transfer, a little heat applied to the dop or stone will allow quick and easy release as the wax softens.

Dopping With Epoxy

The 5-MINUTE variety of Epoxy is useful as a dopping agent when a strong bond is required or when a bit more heating is expected during polishing. You will need the extra bond strength when cutting stones of very small size. The limited bonding area on tiny stones results in a much weaker bond than normal. Extra heat is often generated in polishing corundum. The Epoxy can withstand more heat than wax or cyanoacrylates. Some faceters use the slow-setting regular Epoxy, but I cannot see a good reason for its use.

Many of the same precautions apply to the use of epoxies as were enumerated for the cyanoacrylates. Epoxy will not so readily bond fingers together. It takes at least 15 minutes of steady, light pressure during early setup and needs about an hour or more of room temperature setup before cutting begins. Because of the slower beginning of epoxy setup, I use the transfer fixture with an opposing dop to apply the early light pressure needed for a strong bond. A clean dopping surface is required, although epoxy will bond to a rough surface. Again, experiment with various brands and choose one you like. I have had good results with the DEVCON brand. Do be aware that epoxies age on the shelf, especially after opening the tubes.

The most important phase of epoxy dopping is the mixing of the epoxy and the hardener. Squeeze out Equal lengths of epoxy and hardener side by side on a hard, clean surface. (Or follow directions on the tubes.) Mix with a toothpick, pushing one substance into the other, lifting and FOLDING one element into the other. Conventional around-and-around stirring incorporates too many air bubbles that can reduce bond strength. Get a pastry cook to show you how various ingredients are ďfoldedĒ one into another. The principle is the same. Mix for at least a minute before application.

Transfer Dopping

Transfer dopping must be done carefully to maintain perfect alignment of the stone. If the alignment shifts, the girdle thickness will vary around the stone. Facets that should meet perfectly will, consequently, not meet. The table facet may be off-center, or irregular in shape; like facets may differ in size, etc.

Transfer When Wax Or Shellac Dopping Has Been Used

When wax or shellac has been used for the initial dopping, I strongly suggest that transfer dopping be done with cyanoacrylate glues. It is easier and helps to avoid that disastrous alignment shift. Mount the initial dop and the partially cut stone in one transfer fixture clamp with a suitable, second concave dop in the opposing clamp. Using a toothpick, spread a thin layer of the Super Glue inside the concave dop, only about 2/3 of the way to the bottom. The reason: The sharply pointed end (culet) of the stone is weak. If Super Glue extends to the culet tip, the tip may fracture when slight stress is applied as the stone is separated from the dop.
With the stone bonded to two dops and still mounted in the fixture, a simple procedure is used to prevent more than minor heating of the second dopping, i.e., the dopping at the pavilion. Cut a strip of cotton cloth about 1 1/2-inches long by about 1/2-inch wide. Dip the bit of cloth in water and wrap it around the dop/stone juncture at the second dopping. That is the one you want to retain for cutting and polishing the crown. Water has the strange property of absorbing heat itself without showing much increase in temperature. The wet cloth absorbs heat traveling into the stone when the first dop is heated for removal.

Next, loosen the fixture clamp on the first dop only. Stick the sharply pointed tip of a scribe or ice pick slightly into the metal of the first dop at a point near the stone. Only VERY SLIGHT scribe penetration is required. Apply the torch flame to the center of the first dop, the one to be released from the stone, while applying a small pressure to the scribe. The pressure should be applied directly away from the stone. The first dop will quickly release. Gently clean off still-adhering wax or shellac and continue with crown cutting.
The steps leading to the actual removal of the original dop are far more difficult to describe than to accomplish. A practice run or two should ensure expertise. Note that scribe penetration into the dop is so slight that it does not harm the dop.

Transfer When Super Glue Or Epoxy Was Used Initially

In this case, we have two options: 1) Attack or similar strong solvent can be used, or 2) heat can be applied and the scribe or ice pick used as described above. Whichever option is chosen, the transfer dop must be attached as described above. The super glues and the epoxies are all suitable for transfer dopping.
If option #1 is chosen for removal of the initial dop, then a test tube or bottle must be used to hold the strong and somewhat noxious fluid. I find this method good for emeralds and opals. The fluid level in the tube or bottle must be just sufficient to reach slightly above the initial dop, leaving the transfer dop totally above the fluid. Also, it is best if the vapors from the solvent are blocked from reaching the second or the transfer dopping level. A small fan, played on the transfer dop, will remove the vapors before they can attack the transfer dopping. Wait 12 to 24 hours for the solvent to dissolve the initial dopping. The solvent works slowly at temperatures below 70 degrees F.

The solvent should be used in open air or in a well-ventilated garage at several yards from the flame of a gas-fired water heater or furnace. Care should be taken to assure that the vapors are not inhaled, nor the liquid spilled on the skin or gotten in the eyes. The solvent must be kept and used beyond the reach of children. All this sounds very serious, and it is; but Attack is probably no more dangerous than insect spray, gasoline or a number of other substances kept around for home use. I forgot to mention that Attack and similar substances make very efficient paint removers!

If option #2, application of heat is chosen to remove the initial dop, proceed as described for removal from wax dopping. However, be sure there is sufficient water-soaked cloth wrapped around the dop/stone junction of the transfer dopping. Then, apply heat as fast as possible. Get that initial dop off as soon as you possibly can!

Removal Of The Finished Gem

Any of the above options can be used to remove the finished gem from the dop. For the average run of stones, however, I prefer to place the dopped stone in a small cooking pan. Fill the pan half-full of cold water and add a squirt of liquid dish washing detergent. Bring the water to boiling and let it boil for a couple of minutes. Use forceps to lift stone and dop out of the pan. Apply modest finger pressure to unseat the stone. Still-adhering dopping material can be easily removed while the stone is still hot. I have never damaged a stone this way, probably because the heat rate-of-change is slow enough to cause little strain within the stone.
If your stone is quite heat sensitive, and the idea of raising its temperature to that of boiling water disturbs you, then you might consider an opposite course. Place the dopped stone in the freezer propped up a bit so the stone itself rests on nothing. After 15 minutes, apply modest finger pressure to free the stone. This seems to work well with Mexican opal and the somewhat heat sensitive gems. If your gem is really heat sensitive, use solvents.

And, that is the whole story, folks. I have probably told you more than you ever wanted to know about dopping and transfer. However, I know that some day you will remember and use some process that doesnít interest you at the moment. Most important, do not be afraid to modify and adapt these procedures to better serve your requirements. Thanks for reading.