Dopping with a magnet .

by John Hamer

This is a method designed to give you full control of dopping, so that the stone is dopped in what you consider to be the perfect position first time, and every time. It was designed for dopping with wax, and makes dopping with wax much easier to get right. There is no pre-warming of stones, and no need to ever touch a hot dop, hot stone, or hot wax. It should work equally well with any type of glue or glue/wax methods of dopping. Having full control, means that it is perfect for getting the maximum yield from expensive rough, dopping a stone for repairing wear and tear, or for re-cutting a native cut stone. The idea will work for every faceting machine if you use a suitable transfer jig.  The basic idea is simply to temporarily support the stone with the table horizontal, slide it on the magnet so it is perfectly positioned, then transfer dop it.

The first step is to prepare the rough, and mark the centre. You can simply grind a flat at the table position, then mark where you think the centre of the stone should be, and dop without further pre-forming. You could also grind the girdle to a suitable depth, just on the length and width, then you could mark the centre accurately by measurement, giving maximum yield for more expensive rough. You could also completely pre-form the stone before marking the centre if that is your usual method, though this tends to reduce yield.

The next step is to support the stone in the short dop with the table horizontal. After cleaning the stone in alcohol, assemble the equipment and stone in the transfer jig as shown. The stone is held in position solely by friction.

Heat the top of the small dop (not the wax), while using some downward pressure on the flat dop.

  As the wax softens, the stone will sink into the wax until it makes contact with the short dop. You are not trying to make a good bond, so the wax does not have to get very hot. This stage should now be complete, with the table held in a horizontal position by the wax, and the stone supported firmly on the short dop.

Using the pointed dop, the stone can now easily be centred to precisely where you marked the centre, simply by sliding the short dop in the necessary directions on the magnet. For a non round stone, it can also be rotated to line up any side with a pin, groove, or other locating device. The more accurately you can mark the centre, the more accurate the dopping will be. Shown is the stone centred, and lined up in relation to where the locating pin will be.

Now it is simply a case of transfer dopping. Carefully wrap wet paper around the short dop, avoiding getting the table wet. Check it is still central, then change the pointed dop for the dop you have prepared for use. I always paint the table with varnish at this stage, though this is optional. I use varnish made with shellac flakes, which dries very quickly under the torch flame and there is no need to wait for it to dry hard. The varnish makes the centre marking hard to see, as shown in so be sure it is central before varnishing.

Slide the prepared dop down to just above the stone, and begin heating as shown. Keeping the flame moving all the time over the stone and the dop above the wax. At first I concentrate a little more on the dop to ensure that the wax softens in the cone of the dop. When the wax begins to slump onto the stone, press the top dop down until it makes contact with the stone. Now, keeping the flame moving slowly, concentrate the flame onto the stone just away from the wax as shown, and the wax should flow to the hotter area like soldering. The varnish makes the surface compatible, which also helps. It doesn’t have to flow much to make a good bond.

After cooling, wrap the wet paper around the top dop, re-wet the paper if necessary, and remove from the jig. The short dop can now be removed. A steady light pull on the short dop as it is warmed, and it will quickly come off. It can be left on the magnet for this if you prefer. The wax is then cleaned off the stone with a hot knife, and wiped back onto the short dop. This wax doesn’t have to be new, as you are not trying to get a good bond on the short dop; old wax can be used and reused many times. You should now be ready for faceting with a perfectly dopped stone.

All this may sound very complicated and time consuming, but it is not. I would not dop any other way, even for cheap rough, partly because the control gives confidence in the bond as well. For professional cutters, the extra yield of expensive rough makes the small amount of extra time, time well spent, while for hobby cutters the extra time is well spent for all rough. There are just 5 easy steps, some of which you have to do anyway. 1, prepare and mark the rough, 2, make the table horizontal with the flat dop. 3, move the stone into the ideal position. 4, dop the stone. 5, remove the short dop.

Enjoy your faceting, John Hamer.

For a copy of John's original article please go to:  http://gems-bydesign.com/faceting/dop/MagnetDop1.html

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