Making a Channel Work Bola, by Edwin Elam
Originally published as a two part article in Rock & Gem Magazine, Apr/May 2002
|If you have done some silversmithing and some lapidary work, you may be ready to combine the two skills and try your hand at channel work. The pattern I have chosen for this project is ideal for a beginner, and yet is versatile enough to appeal to the craftsman who has already done some channel work.|
This pattern works well because all the stone pieces can be cut on ordinary cabbing equipment, and because it has none of the elements
that can cause difficulty, such as C-shaped inside curves or shapes with long, sharp points, both of which are difficult to cut. Also,
it requires no specific colors for the stones. Two or three contrasting colors of stones are all that is required to make this
piece work well; I chose black onyx, a dense, red moss agate, and yellow Paint Rock agate.
To start this project, make at least three copies of your pattern. You will want one for your file, one to use as a pattern for the stone cutting, and one to work on. I use tracing paper or onion-skin paper for the pattern I will use to work on because the thinner paper burns out easier when you reach that stage. Ordinary typing paper will be OK.
Pin your working copy down to the fire brick using four straight pins. Push the pins in until the heads are flush with the surface of
Prepare the pins that will hold your channel wires down to the brick and on your pattern. Snip the heads off the pins and bend a hook in the top end using your chain-nose pliers. Insert about 1/8 inch of the pin into the jaws of the pliers, perpendicular to the jaws. Holding the pliers in your dominant hand, use the index finger of the other hand for an "anvil." Press down hard and bend the hook up until it is perpendicular to the shaft of the pin. Reversing your pliers, bend the hook 15 to 20 degrees past vertical.
It is important that the pins be prepared properly. The sharp bend in the pins makes pinning the channel wires to the pattern more precise, and holds the wire in place for soldering.
I used 25 pins for this piece. As a general guideline, pins will need to be placed about 10mm to 12mm apart. I try to keep my pins
4mm to 5mm away from each joint, because if your flux runs over to a pin, your solder may do so as well, soldering the pin to the channel
wire. If this happens, you must cut and file the pin off your channel wire.
Measure the total length of the wires for your piece and cut off that length from the coil. Straighten your wire by placing it on a smooth surface and rubbing down the length of the wire with the handle of a ring mandrel, a block of wood, or something similar. Your wire must be completely straight. You will find that if the wires have little bends in them, you will have a hard time cutting your stones to fit.
You are now ready to cut, file, shape and pin down your first wire. I usually choose the longest wire in the pattern. In this project, do the perimeter wire first.
Measure the length of wire required for the outside wire, file one end square, and mark where each bend will be made. I put the joint
in the center of the short wire at the bottom of the pattern instead of in a corner because this is a symmetrical piece, and if you put
your joint in a corner you will be able to see a difference between the soldered joint and a bent joint.
File the end of your wire square, and using your chain-nose pliers, make the bends in your wire. Place the wire on your pattern and adjust it until it sits exactly on the lines of your pattern. Pin the wire in place.
Use your chain-nose pliers to put the pins in the brick. They should start perpendicular to the brick and go straight down. Push the pin
most of the way in, turn the hook to the right position, and use the side of your pliers to finish pushing the pin down. Remember that
your objective is to pin your channel wire on the lines of the pattern, to keep the wire perpendicular to the brick, and when your
piece is pinned down, to have the wires level across the top of your piece.
Once the outside wire is in place, cut the remainder of your wires. Use your jeweler's saw with a 4/0 blade. File the ends square and pin in place. Check that the wires are perpendicular to the brick, your joints are tight, and the wires are level across the top before going to the next step.
You are now ready to burn out the pattern. Find a suitable container, one that can be sealed to preserve your solution, and add
a few ounces of denatured alcohol. Add boric acid to the alcohol, shaking the solution to dissolve the acid. When the acid stops
dissolving, the solution is ready to use. Pour a couple of tablespoons of the solution over your piece, being sure that you get
the solution over all your channel wires. Light your torch and set the solution on fire.
Allow the alcohol to burn out. The paper of your pattern will probably not be completely charred. Use your torch to char the remainder of the pattern. When this is done, use your soldering pick or a toothpick to gently rake out the ash of the paper pattern.
The purpose of the operation you have just completed is to get rid of the paper pattern and to keep the ash from interfering with your
soldering of the joints in the channel wire. The boric acid/alcohol solution also cleans your silver and helps prepare it for soldering.
Before you begin soldering, let me cover some of the materials, equipment and methods I use. I use a Goss torch with a #2 and a #3 tip. The Prestolite torch is of the same design and has the same tip sizes. The #2 tip (medium flame) is used for the first part of the soldering and the #3 tip (large flame) is needed to solder the channel wires to the backing plate.
I have always used a paste flux, specifically Handy Flux. If you are accustomed to using other kinds of fluxes, I would suggest you use them. In this project and in my classes, we never use anything except easy solder. This is the solder that one of my catalogs specifies as Braze 650, which is 65 percent silver, 20 percent copper, and 15 percent zinc, and has a melting point of 1,240 degrees. This may not coincide with what you were taught in beginning silversmithing, but everyone who teaches channel work uses this method. I cut my sheet solder into snippets roughly 2mm by 2mm.
One final check of your channel wires and you are ready to begin soldering. I use the pick soldering method to solder the joints of
the channel wire. Soldering picks made of titanium or alloys are available from tool suppliers. You might want to buy one because
once you learn pick soldering, you will find yourself using it more and more on lots of different silversmithing projects. A homemade
pick will work well. Any stiff steel or iron wire is suitable. I use bicycle spokes. The wire from a clothes hanger is also suitable.
For a handle, drill a hole about 3/4 inch into a 2-1/2 inch piece of wooden dowel and insert a 4 inch to 5 inch piece of wire in it. Sharpen the other end of the wire using a file. You may have to file the tip occasionally to keep it clean.
Flux each joint in the channel wire. I use toothpicks to apply the paste flux. Dry the flux with your torch, using the #2 tip. Place a snippet of solder for each joint, plus a couple extras for the ones you drop, over on one side of the brick, spaced about 1 inch apart.
To start soldering, take your torch in one hand and the soldering pick in the other. Melt a snippet of solder until it balls up, then move the flame away. Just touch the ball of solder with the point of your pick, and the solder will adhere to it.
Place the ball of solder on top of the channel wire at a joint. Warm it a bit with your torch, and it will turn loose from the pick and
sit on the channel wire. If the ball of solder falls off, do not try to retrieve it; melt another snippet and try again. It may help if
your brick is positioned so that you can rest the wrist of the hand holding the pick on the edge of the bench. If you have not done pick
soldering before, it may help to actually "rehearse" the steps before you light your torch.
When the ball of solder is sitting on the channel wire, move the flame of the torch in a circle around the joint until the solder runs. Continue until you have soldered all the joints. The pick soldering method is easy and fast, once you learn the process. If, for whatever reason, you cannot get this method to work for you, you may go back to the conventional method of placing a snippet of solder at each joint and warming the whole piece until all the joints have been soldered.
Take the frame of your piece off the brick and pickle it. Check the soldered joints. If any areas in the wire have bent from the
heating, you can do some slight adjusting and straightening.
Check the framework against one of the patterns that you saved. Once you are satisfied with the framework, you have to file the back of the frame so that it sits flat on the sheet of silver you are using for a backing plate. I place the frame on my fingers, and using a fine-cut flat file, gently file in different directions until it is completely flat. You can also put a medium-grit sandpaper on a flat surface and gently lap the piece until it sits flat on your silver sheet without any gaps showing.
Position your frame on the silver sheet and mark around the outside. I find a fine-tip, permanent-ink pen ideal for this. Saw out the backing plate using your jeweler's saw with a 4/0 or finer blade and some saw blade lubricant. If you want to stamp your backing plate with a "Sterling" stamp, do so now.
To solder the channel wire frame to the backing plate, pickle both pieces to be sure they are clean. Lightly coat the whole surface of the backing plate with paste flux. Put the backing plate on your fire brick and align the channel wire on the backing plate. Dry the flux with your torch.
Position five or six snippets of solder inside the pockets of the frame. They must be flat on the backing plate and also be touching a channel wire. Just space them around within the frame. You may want to warm the flux again to help stick the solder in place. Change your torch tip to the #3 tip. A reasonably large flame is required for this operation. Once again, it may help to rehearse the procedure before lighting the torch.
|With your soldering pick, raise one side of the backing plate about 3/4 inch off the brick. Rest the soldering pick on the edge of the brick and rest the hand holding the pick on the edge of the soldering tray. Direct the flame of the torch onto the brick under the piece. Move the flame back and forth slowly under the piece. This process may take longer than you might expect.|
While you are heating the brick, watch the solder on top of your piece. When you see your solder snippets start to melt, quickly
lower the piece onto the hot brick and move your torch flame rapidly around the top of the piece until you see the bright
liquid solder flash under all the channel wire.
I know that if you have had a course in silversmithing, you would be inclined to try this operation on a soldering screen. I have done so, and the piece was destroyed because the backing plate warped before it soldered. Look at the pictures and follow the directions, and you will be amazed at how well this works.
For a bola, I prefer to use the "figure 8" finding. This requires 3-1/4 inches of 14 gauge round wire. Anneal the wire and wind it
around a 3/8 inch dowel, the smooth portion of a 3/8 inch bolt, or something similar, to form two complete loops with the ends pointing
in opposite directions in a flat plane. Turn the ends back so that they are at right angles to the loops.
File the bottom of this finding so it will sit up straight on the backing plate. Center the finding on your bola, about 1/2 inch from the top. Flux and solder the center loop, as well as the ends.
Using needle files, fine sandpaper, tripoli and rouge, clean up and polish the silver work. Cover the back and edge of the bola with masking tape to keep from scratching the polish as you handle the bola during the stone fitting.
|I would suggest for your first channel work piece that you choose stones such as agate and jasper. Avoid any type of stone that you might have trouble polishing. Slabs for channel work need to be 3mm to 4mm thick. They are not generally available on the market. If you do not have a slab saw, perhaps you can cut enough slabs on your trim saw for your piece. The great thing about channel work is that it does not require a lot of stone, so three small slabs of the color you want to use will be sufficient. If you must work with slabs that have been cut 7mm to 9mm thick for cabbing, you must thin your stones down, either on the trim saw or by grinding on the coarse wheel of your cabbing machine.|
|You can make patterns for each piece of stone by cutting apart one of the patterns you saved. I use an ink pad to make an exact copy of the piece, and then cut apart the pattern for each stone. The ink pad method gives you a reverse impression, so remember to put the paper pattern face down on the stone. Mark around the pattern with a cab marker or a fine-point, permanent-ink pen. These patterns serve only for trim sawing. The fitting of each piece in its pocket must be done by grinding.|
|Your goal is to fit each stone so that it will go into the pocket without forcing and will drop back out. There should be no significant gap between the stone and the channel wire. This is not as difficult as you might imagine. If you have an adjustable cab rest, set it so that the edges of the stone are 90 degrees to the face of the stone. If you don't have a cab rest, determine the point on your wheel that will give you the right angle, and always try to grind at that point. The tendency is to taper the edge slightly when you're grinding for fit. If you taper your stone, when you grind down the face of the piece to finish the stones, you may end up with gaps between the stone and the channel wire.|
|When I start grinding a stone to fit into the pocket, I get one edge so that it fits and then proceed around the stone. Grind a little and look a lot! Fitting the stones precisely may add a few minutes to the cutting of each piece, and you might have to go back and re-cut a stone if you make a mistake, but the quality of craftsmanship shown in your finished piece will be well worth the extra effort. Mark the face of each piece and its proper orientation when you finish it using an aluminum cab pencil. This will aid you when you begin to epoxy the stones into the pockets.|
Use a fairly generous amount of a clear-drying epoxy in each pocket and keep a paper towel, moist with alcohol, handy to remove any
epoxy that squeezes out.
When the epoxy has set, grind and polish the surface of your channel work. This is a fairly straightforward process if you are using a flat lap-type machine. Use the coarse lap to grind the surface down until you have touched all the channel wires and all the stones. This is easy to see, because the silver will appear brighter where the lap touches it. After that, follow the steps you would use to polish any flat piece.
I finish my channel work on a conventional-type cabbing machine. I am presently using a Diamond Pacific Genie, which has 80, 220, 280, 600, 1200 and 14000 grit wheels. I have a large, slow-speed leather buffing machine, so I finish off with tin oxide on leather. Many people have expressed a fear that the silver is somehow going to contaminate their wheels or polishing buffs. I have done a lot of cabbing and channel work over the years using a variety of wheels and buffs, and have never seen any adverse effects.
To make a handle to control the piece, I take a 12-inch piece of string and tie the ends together. I loop the string through the
finding on the back of the piece. Holding the piece by making a fist with my right hand, and holding the string between my thumb and
forefinger, I place my left hand under my right hand and use my forefinger to support the bottom of the piece.
Try to move the piece straight up and down against the wheel. The process now is exactly what you would do if you were cabbing a stone. Each step is removing the scratches left by the previous wheel until you have polished the piece. You will find a fine wire or lip of silver turned down on the edge of the piece. You can remove this with a fine sanding stick or fine-cut file.
Touch up the silver with a polishing cloth and wear this beautiful bola with pride.
Edwin Elam was involved with the lapidary hobby from the early 1970s until his death in February 2010.
He was AMLS' Nominee for Southeast Federation Rockhound of the Year for 2008.
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