Dopping with Adhesives
by Charles W. Covill
Doping stones for faceting, is like all other aspects of faceting, a personal thing, for some people it comes naturally for others it takes time to learn, then there are the few who never master that part of the hobby. I have set down several things that have worked for me over the years. My hope is that some of the methods listed here will be of help to you, and that you may be able to take to them like a duck to water.
Because I cut several stones at a time, my process is a little different and might be a little time consuming for a facetor cutting one stone at a time: however I use the same procedure whether I am dopping up one stone or a dozen of any kind. I have completely gotten away from wax and heat of any kind. I have had too many stones shift or come off the dop with wax, and I have seen some remarkable color changes with heat, and have had quite a few stones come apart because they have gotten too much heat, either in dopping or polishing.
I have tried just about every type of super glue on the market, and have finally come up with a winner. It has long shelf life, is fairly resistant to water and can stay on the dops for months without weakening. It does not need to be refrigerated between uses. Its DAP-CA (with a pink label) made by PACER TECHNOLOGY, Rancho Cucamonga, CA 91730. It comes in several sizes. I prefer the one-ounce bottles because I use quite a lot of it. The color of the label tells you the thickness and set up time of the glue. You should be able to find this in the better hobby shops. I have never seen this cyanoacrylate in drug stores or discount places.
Using the cyanoacrylate
When faceting I always do the pavilion first. So I cut a flat spot on the rough with a 170/200 disc, I use the 170/200 disc because its quicker than using a 600 disc, I have found with this glue that the course surface is not required for a good bond. A smooth saw cut or a 600 or finer finishes works well with this glue. I then take a brass scriber rod and with a rapid design circle template inscribe a circle on the rough the same size as the dop, where I want the table of my finished stone to be. Next I clean the stone and the dop with ethyl alcohol, (most other cleaning agents leave a film that tends to weaken the bond) then apply the glue to end of dop. I prefer stainless steel or brass dops; aluminum dops oxidize very quickly and set up a film that prevents a good bond. I apply a drop of glue so that there is more than enough glue to cover the end of the dop. Holding the stone in one hand and the dop in the other, with the dop on top, bring the two together gradually turn or twist the dop until you feel resistance (the dop must be flush with the stone). Now turn the stone and dop over so that the stone is on top. You may release the stone now and gently rotate the assembled stone and dop; the excess glue will form a fillet around the stone and increase the strength of the connection (this is similar to a small fillet weld and gives a little more holding power to the glue). SOME WORDS OF WARNING SUPERGLUE LOVES HUMAN SKIN AND WILL BOND YOU TO SOMETHING INSTANTLY. Do not let the glue come in contact with you and the dop stick at the same time. If this should happen you can release your fingers by soaking your fingers in finger nail polish remover. I now set the mounted stone and dop in a dop holder. Usually by the time I have mounted a dozen or so stones the first one is ready to proceed. At this time I usually preform the rough on my faceting machine either by grinding or sawing. If the rough is big enough those sawn off pieces are then mounted to cut other stones.
I might add that if I start with preforms I use a cone dop in the bottom of my transfer stand, set the alcohol cleaned preform, culet down, in the cone dop. Apply the glue to the flat dop and place it in the upper position at the top of the transfer stand. Now bring the dop into contact with the stone. Try to rotate the stone, this will center it and bring it into good contact with the dop. When using two transfer stands (Jarvi's Facetron) by the time the second one is finished the first one is ready to be removed from the stand. I also use this method of orientation when I am repairing stones. The glue holds well on a polished table.
During the preforming and cutting of the pavilion, I hold the stone not the dop. After the pavilion is cut and polished I am ready to transfer the stone. For my transfer I use a two part five minute epoxy with a couple of things that I have found that protects the culet of the stone from breaking off. First clean the stone and the dop with ethyl alcohol, then apply a speck of Vaseline to the culet, and in the bottom of the cone dop. The Vaseline will prevent any bond from developing between the culet tip and the epoxy. To dispense the Vaseline I use a 3cc or larger syringe with out the needle; you can purchase these at your local drug store or ask your Vet. or Doctor to give you a used one. After cleaning the stone and dop, I dip the culet of the stone in the Vaseline so that there can be no bond between the culet and the epoxy. Then place the dop with the stone in the top of the transfer stand. The cone or V dop is placed in the bottom of the transfer stand (I use a V dop only as a last resort, usually a cone dop will do for most shapes). The reason I shy away from the V dop is because I use a FACETRON, the dops are keyed and sometimes reorientation of the stone is required, this will not be the case with the cone dop. I started using the Vaseline to keep the culets from popping off, I orient the stone for best color and this usually means on the C axis. With topaz I was loosing quite a few cutlets because of the cleavage plane.
Epoxy goes through some very severe thermal changes as well as expansion and shrinkage during its curing process. These changes put very severe, stresses on the gemstone and can actually pull the gemstone apart. If the epoxy is bonded to the sides of the dop and the sides of the stone, when the epoxy shrinks, as it does, it puts tension on both the faces of the stone and the dop. I lost several culets on topaz and have had pits pulled out of the faces of facets on topaz and other gemstones. The Vaseline was part of the solution, the other I discovered after trying many additives to the epoxy when mixing.
The best solution was something that would mix with the epoxy and hold its shape as the epoxy setup and then become soft and leave voids for the epoxy to expand and shrink around. I also found other advantages one was it told me when the epoxy was thoroughly mixed. What I found was NABISCO'S Instant CREAM of WHEAT! I store the cream of wheat in a used spice container with a shaker top, which my wife donated.
I cut my used paper from my printer into four pieces roughly four by five inches. One of the uses for these pieces of paper is to use as a disposable surface to mix my epoxy. With a clean piece of paper I lay down a bead of epoxy and hardener side by side, being careful not to let the nozzles of the bottles come in contact with the other material. Then I sprinkle the cream of wheat over the epoxy and hardener, pick up the paper and shake the excess cream of wheat into the trash. Now with a clean knife blade (ethyl Alcohol again) I fold the epoxy over and over and round and around until the cream of wheat is evenly distributed. (I don't use a toothpick because I feel it stirs but does not mix the epoxy) Using the Vaseline and the cream of wheat I have eliminated 98 % of my culet and chipping failures. Then using the knife blade as a spatula I scrape the mixture off the paper and place it into the cone dop. Fill the cone dop up to the rim. I then lower the stone into the epoxy; the cream of wheat is still hard enough to keep the stone from touching the edge of the dop. Once again I usually transfer my stones two at a time, after removing the excess epoxy from the outside of the dop with a piece of paper towel wet with alcohol. (Not necessary to remove all the epoxy as it is easily removed in the next step of transferring.) I then set the transfer stands aside for the epoxy to cure. Usually over night this does not pose a problem because I can facet other pavilions, or go for a walk with the wife, read or watch TV. Five-minute epoxy does not gain sufficient strength for faceting in five minutes, if you try to use it too soon the stone can shift and your alignment will be messed up. That is why I try to let it set for several hours. It is strong enough so that after I have faceted a couple more pavilions, I can remove the assembled dops and stones from the transfer stand and place them upright in a dop holder. This will allow me to transfer two more stones. The cream of wheat will break apart easily when the epoxy expands, it has very little tensile strength, and it will compress when the epoxy contracts. The cream of wheat also serves as a path of weakness for the chemicals to penetrate the epoxy and aids in a speedy removal
Of the epoxy the two brands I have had best results with one is 5 MINUTE QUICK CURE EPOXY by BOB SMITH INDUSTRIES, Atascadero, CA, the other is also made by PACER INDUSTRIES its called Z-POXY. Most of the other epoxies I tried were not uniform in strength or set up times. Some had short shelf life and some failed in direct sunlight. The most disappointing ones were the ones in twin tubes with a plunger, these seemed to get contaminated and the whole batch would set up. Some from automotive supply stores had set up while standing on the dealer's displays. Because of the volume used I purchase the Z-POXY in the 4 Fl. Oz. Bottles.
Separating the glue side from the epoxy side
Next I take the stones with the dop sticks top and bottom, place them in and old Olive jar. I had previously soaked a piece of old broom stick approximately 2 inches long, in acetone until it was saturated and would no longer float, this is kept in the olive jar and does not require as much acetone to keep the jar approximately half full. When the dops are placed in the jar the acetone will cover both the superglue and the epoxy joint. (It's not necessary to have the level above the epoxy joint: but if it is it won't hurt the epoxy, and you don't have to worry about which joint is on top) I try to place the dops in the acetone before breakfast, then after breakfast the cone dops containing the stone can be removed (it usually takes about an hour for the superglue to release depending on size of dop stick, how long and how much use the acetone has received). Because Acetone is toxic the olive jar containing the acetone must be kept tightly sealed except for the time needed to place and remove the dops. (ACETONE IS EXTREMELY FLAMEABLE AND SHOULD NOT BE USED AROUND OPEN FLAMES) For removing the dops from the acetone I recommend the 7 inch long stainless steel jewelers tweezers. With these tweezers you can remove the dops and easily reach stones that invariably will some how wind up on the bottom of the jar. The 2-inch dowel or broomstick in the jar will keep all the dops lined up around it and they will be visible for easy retrieval. When the cone dops with the stone are removed from the jar I clean them with a paper towel soaked with alcohol. At this time any excess epoxy is easily removed with your fingernail or a knife. I like to remove the epoxy from around the girdle line of the stone; this will aid in seeing the line between the pavilion facets and the girdle. This also helps you judge the thickness of the girdle when cutting the crown facets. The acetone will not have penetrated deep enough into the epoxy between the gemstone and the inside of the cone dop to affect the bond between them. When you remove the flat dops from the olive jar they should also be cleaned with alcohol before returning them to the dop holder. Acetone evaporates very fast and the fumes can be toxic so you should avoid breathing the fumes as much as possible.
You can start faceting the crown as soon as you like however if you have fears that the epoxy may be damaged, and will not hold, you can put a drop of the super glue at the joint between the stone and the dop. The glue will run around the dop and completely seal it. If you blow on this joint the air flow and the moisture in your breath will speed up the setting time.
Removing the Epoxy.
After the crown and table are completed, its time to remove the stone from the dop stick. (To speed up my work I do several crowns and then several tables before I remove the stones from the dop stick) To remove the stones from the dop stick I use a metal hinged standard wide mouth mason jar with a replaceable rubber gasket seal. These can be had at grocery stores; hardware stores and canning supply stores. I have made a small round metal tray with small holes in the bottom, and a wire handle coming out of the middle. The tray is just small enough to go inside the mouth of the Mason jar. The handle is long enough to extend within about one half inch of the jar lid when closed. The holes in the bottom will drain the tray when it is removed, yet will keep most of the epoxy residue inside for easy dumping. The sides of the tray must be tall enough to keep your dop sticks from falling out. The tray can be made from metal hardware cloth, a round metal jar lid (punch holes with an ice pick, flatten the protruding edges around the holes with a hammer. Be sure you back up the metal when flattening the edges of the holes, another hammer facing works well for this.) I used a piece of 0.03125" thick steel plate that already had small holes in it. For the handle run a piece of 14ga. Wire through a hole at the center and bend to 90 degree under the basket. For handling put a finger sized loop in the other end.
The jar has two chemicals in it. First place about one and a half inches of METHYLENE CHLORIDE (Attack, or Formby's Paint Remover) in the bottom of the jar. Next add about one inch of tap water. The chemical will dissolve the epoxy and super glue. Methylene Chloride is toxic and fumes from it should not be inhaled. It also will evaporate very fast. The water will float on top of the methylene chloride and form a vapor seal to keep the fumes from escaping and the methylene chloride from evaporating. Keep the jar closed when not loading or unloading. When using the methylene chloride without the water, the rubber seal on the jar would deteriorate quite often, and the chemical would escape. The addition of the water has solved both problems.
I load the tray outside the jar and then lower it into the chemicals; I have on occasion further loaded the tray with up to a dozen dops, its best to use those tweezers for this. Try to keep a little clearance between the end of the dop with the stone and the edge of the basket, this will let the stones fall inside the basket, as they become free. Let the stones soak over night, then the stones will be free from the dops and the epoxy will be dissolved. Remove the tray from the Mason jar, and set it on some of those pieces of paper, this will prevent harm to the surface where the tray is placed. I use the tweezers to remove the stones and place them on those papers, and then the dops are removed and placed on another set of papers. The basket is dumped by gently taping it on the edge of the trash container, then the basket is returned to the jar and the jar is closed.
Now clean the stones with a paper towel and ethyl alcohol, clean the dops with the alcohol be sure there is no dissolved epoxy residue inside the dop, after the dops are cleaned inside and out return them to your dop holder.
Sometimes I find a situation where I must remove the stone from the epoxy filled dop, without an overnight wait. A customer needs it sooner or the Methylene chloride just didn't do the job. In order to do this in a hurry; place the epoxy dopped stone in a small aluminum pan. Start by running room temperature water at the kitchen sink over the stone, gradually increase the temperature by increasing the hot water and decreasing the cold water until its as hot as you can get it. Now pour out all the water except enough to cover the stone, place the pan on the kitchen stove and bring the water to a boil. The stone should pop out of the dop about a minute after the water starts to boil, if it doesn't take a fork and dip it in the water then place it at the junction of the stone and dop. Push or twist on the fork the stone will pop out. Turn off the heat and return the pan to the sink. On the opposite side of the pan from the stone start a small stream of the hot water, gradually increase the stream and at the same time gradually go from the hot to the cold water. Be sure your water is not flowing directly on the stone. When you reach the cold stage you can remove the stone and the dop, and empty the pan. Your stone will come out clean, but your dop will need to go back to the methylene chloride bath or you can remove the epoxy with a knife. With this procedure the stone will never reach a temperature over 212 degrees. If you have use for a mold of the pavilion of your stone, you have one with the epoxy filled dop.
Using super glue on both sides of the transfer
You can use superglue on both sides of your transfer if you desire, if you do this be sure your acetone does not come in contact with the second side of your connection. Instead of epoxy fill the cone dop about three fourth full with the super glue, lower the stone into the glue. Now apply a cyanoacrylate accelerator to the glue in the cone dop. It will instantly set the super glue: but there is a problem with all chemical reactions, and here there is a real heat build up. I do not advise this with heat sensitive stones, and you could get burned. The same two California companies mentioned before once again make two of the best cyanoacrylate accelerators I have found. ZIP KICKER by PACER INDUSTRIES and INSTA-SET by BOB SMITH INDUSTRIES. Both of these evaporate very rapidly and a bottle not tightly sealed will be gone overnight!
Using heat to release the connection
You may release a stone from superglue connection by heating the dop stick that you want to remove, while keeping the other side of the connection cool. To do this apply heat to the dop stick. I have used a mini torch made by Leichtung; it uses butane fuel and is refillable by just plugging it into the recharge can. The torch is piezoelectric and ignites at the touch of its plunger. The torch has three different heat settings, low is adequate for removing the dop stick, high works well to thaw the neighbors outside water pipes. You can also use your alcohol burning stove that you use for melting your dop wax. The only problem with the alcohol burner is that the heat is applied slower and more heat can cross through the stone to the other connection. Whichever method you use you must take steps to keep the stone and other dop from getting hot. If the stone gets hot it could change its color, or if its heat sensitive it could fracture. Also the connection to the other dop could become soft and allow the stone to shift. The ideal way would be to fashion a method where the stone and the other dop could be immersed in water with only the connection on the dop to be removed above water. This will work when both ends of the stone are attached with glue. If you can't do this wrap the stone and dop in a paper towel saturated with water. Hold the towel wrapped stone and dop in one hand and bring the other dop into the flame, If it gets too hot to hold better stop and realign your stone with the transfer jig. As the dop gets hot it will tend to let go at the connection as the glue melts. When the dop falls off don't let it come in contact with you or anything else that will scorch or burn. It will be hot! If you can work over a small pan of water, the dop will fall in the water with a loud hiss as the water boils at the dops surface. The dop will cool immediately. Results using this heat method to remove the dop works best for a combination of joints i.e. super glue on one side (the side to be removed) and epoxy on the other side. It is not as reliable when both sides of the stone are attached with super glue. You will need to scrape the removed dop or soak it in acetone to remove the traces of the glue.