"Intarsia Cabochons "
by William Grundke

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   In the December, 1981; and the January, February, March, April, may and June, 1982 issues of this magazine, the author presented the series, The Art of Intarsia. Parts 1 through 7. In this series he began by telling how to elect a design and choose appropriate gem material. Fro there he progressed through sawing, lapping, grinding, cementing and mounting methods, then gave the complete instructions for making a simple intarsia picture, followed by one with more challenge. Part 7 covered some special techniques to achieve maximum effects and beauty.
   This series concerned the making of pictures for framing and display. You can also use the techniques of intarsia to make interesting cabochons with pictures or geometric designs. The methods described in Parts 1 through 7 of the series still apply for sawing and shaping the component pieces. By following those techniques, it is possible to produce cabochons like those shown in the color photos. If you have not yet read the series, please be sure to do so before embarking on a project such as this.
   The cabochons in the color photos are flat faced. Therefore, the very same procedures covered in Parts 1 through 7 of the series, The Art of Intarsia, including flat lapping, will be followed. However, just about all the gemstone pieces for a cabochon will be smaller than some (not all) the pieces for an intarsia picture. Therefore, the technique of attaching a tiny piece of stone to a larger one will be very helpful. You'll find this method described with Fig. 15 on page 55 of the January 1982 issue of this magazine.
   Instead of flat-faced assemblies, some gem cutters prefer to make intarsia cabochons with traditional domed tops. If you prefer this style, you mast be especially careful in selecting gem material since more material is ground away form the edge than form the center of the cabochon. Be sure that gemstone slabs are of even color throughout. Otherwise, as you cut the dome, you may grind into another color, ruining the entire piece. Extra time spent in the selection of material can save you time and grief in the long run.

Figure 1

Geometric Designs
   For most craftspersons, it is easiest to make the first intarsia cabochons with geometric designs. Those shown in Fig. 1 are striking and attractive in appearance. Surprisingly, they are not as difficult to make as one might think. However, they do take a fair amount of time and patience.
   The first step is to select enough material in two contrasting colors - black and white, for instance. The material must be then sawed into thin strips with absolutely parallel sides. If you have a machine, such as the Gy-Rock Preformer Saw, shown and described in Part 7 of this series (June '82 issue), it will do this job very well. Or, with a conventional trim saw it is possible to devise a rip fence like those on wood saws. Be sure that the fence is absolutely parallel to the blade. With a rip fence setup you will probably find that unless you have very tough gem material, you will break a fair amount of strips. Discard any on which the sides are not parallel.
   Check all strips to be sure they are all the same width. When you have enough alternation colors to make the size cabochon you want, cement the strips together as shown in Fig. 2. Be sure to press out excess cement. Epoxy works well for the adhesive.
   When the cement has hardened, make parallel saw cuts perpendicular to the length of the strips (Fig. 3). These cuts must be spaced so that the resulting strips are the same width as the original strips. The new strips should be composed of squares of alternating colors as shown in the diagram.
   The strips of squares are the cemented together, staggering them so that a checkerboard pattern is formed (Fig. 4). After the cement has hardened, saw the assembly to the desired length and cut it into a cabochon.

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.Figure 2. .. . . . . . . . . . . ... . .... ... . . . . . . . . . . Figure 3 .

Cutting and Cementing Techniques
   In making the pieces for intarsia cabochons, it is especially important to avoid undercutting. There is no problem in cutting strips for a checkerboard pattern, but other shapes require special care. If there is any appreciable amount of undercutting, you may grind a cavity when you dome the cabochon. I use a Preformer Saw, or a sawing jig like that shown in Fig. 4, Part 1 of this series (Dec. '81 issue), or any other suitable method to cut straight sides of the pieces.
   Also, because of the problem just described, you cannot make bevels on the undersides of the pieces to form grooves for the cement as discussed with Fig. 16 in Part II (Jan. '82 issue). Therefore, when the pieces have been pressed together, only a very thin layer of cement holds the cabochon together. To give the assembly more strength, you can add a backing as shown in Fig. 5. If you are cutting for display and competition, use a piece of gemstone, preferably of the same material as used for the cabochon. If the cabochon is to be set in a jewelry mounting, the backing can be of gemstone, metal or even plastic. If possible, make the backing in one piece and attach it with epoxy.
   When the assembly is ready to cut into a cabochon, scribe the outline on the face, or attach an appropriate decal to the face, depending on whether you use templates o decals of cabochon shapes. Experts advise cutting the assembly face up, just the opposite of the usual method of cutting cabochons. Grind up to the outline, making the edges perpendicular to face, then bevel the edges and dome the top.

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.Figure 4. .. . . . . . . . . . . ... . .... ... . . . . . . . . . . Figure 5. .

Other Geometric Designs
   Many other geometric patterns can be worked into intarsia cabochons. For instance, you could cut a cross or a star shape of one gemstone and surround it with other materials. Techniques for cutting shapes like crosses, stars and hearts are covered in books, such as Advanced Cabochon Cutting (available at rock shops and from mail-order suppliers).
   If you have cut a star, it can be put into a circular cabochon. To do this, cut pieces to fit between the arms of the star. Each of these pieces should be sawed with two angling sides that match the angle of the intersection of two of the arms. Be sure that these cuts are accurate for a good fit. It is a good idea to make these insert pieces oversize so that there will be excess material to allow room for cutting the circle. Therefore, after the angled sides are cut, make intersecting cuts, starting at the tips of the star and running parallel to the radii of the circle. This will allow you to completely surround the star with a circular border or to cut the circle down to the tips of the star.
   With a cross you could cut pieces to fit inside the arms of the cross which would form a rectangular assembly. Border strips could then be cemented around this assembly so that the cross would be surrounded by a contrasting material.
   Referring back to Part I of this series (Dec. '81), you will find a discussion of geometric designs. The pattern shown I Fig. 1, Part I is an example of how you could build up such a design. Regardless of what design you choose, the techniques covered in the intarsia series apply; build up in units.
Non-Geometric Designs
   And, the same unit-building techniques apply to the building up of an intarsia cabochon with a non-geometric picture in it. A good example is the bola with the image of a cardinal which is shown in one of the color photos. The body of the cardinal (red jasper) was cut as one piece. To it were added the black and yellow pieces to form a unit. From there the intarsia was built up adding branches, leaves, berries and background.
   Actually this bola is two intarsias. The cardinal, main branch, some leaves, etc. are the top part (layer). Other branches and leaves are the bottom layer. These tow layers were then put together, doublet fashion.
Note: If you would like to make a cabochon like this, the book, Artistry in Cabochons by Robert Ferguson (also available form our suppliers) includes a cardinal pattern in several sizes. It also has patterns for many other shapes, including several animals.
   The cardinal cabochon is set in a silver mounting that was produced with standard jewelry making techniques. Note that the dangles on the bola cord tips are edged with silver strips. I find that stone dangles without such edging can break apart when they bang together.
   Also note that the dangles are of a geometric pattern. Here three thin strips were cut and cemented together., then larger pieces of gem material were added top and bottom. Then the shapes of the dangles were cut.
   To add some variety and eye appeal to an intarsia cabochon, you can put some silver into the design. Just cement silver strips to the edges of a nit(s), then cement the next stones to this silver edging.

Figure 6

Some Special Techniques
   It is amazing what can be accomplished with good tools and a little imagination. If you have a saw with the blade mounted on an overarm arbor, such as the Gy-Rock Preformer, you can set the blade for a certain depth and feed a gemstone slab along a guide to cut out a groove. Later this groove can be filled with a single piece stone of contrasting color, or several stone strips cemented together. With a true-running saw, you can cut these strips as thin as 1/8". Make up strips of several colors and cement them into a unit that fits the groove. Strips can be made into striped patterns, much like the beginning of the checkerboard (Fig. 4). Instead of being mounted into jewelry, these small intarsias can be displayed like pictures. The one of the blue jay (see color photo) is an example. Note that it, too, is edged by silver. This intarsia is displayed on masonite with some special decoration. To start the decorative process, some trim pieces in various shapes were sawed from sheet aluminum. Figure 6 is a closeup of one of the trims. Elmer's Glue was used to attach the aluminum pieces to the masonite in the pattern shown in the color photo. An emulsion, Hyplar Gloss medium, was then stippled on quite heavily with a painter's loose camel hair brush, covering the masonite and aluminum trim. When this medium had dried, it was covered with a glazing liquid, tinted to suit with oil colors (the type that come in tubes). The glaze was wiped off with a soft cloth, leaving it only in the hollows. After this had dries a coat of varnish was applied.
   Like the larger intarsia pictures, cabochons of this type offer a challenge to the gem cutter. When finished, they can be worked into a variety of striking jewelry pieces; inlayed in the lids of jewelry boxes, etc.; or displayed on miniature easels or in frames as just described, to name a few possibilities.


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