(The Rascal)

Commessa Di Pietre Dure - A Florentine Mosaic
by Olive Colhour

Part II

"El Picaro" (1967 - 14" x 16")

   In making my gemstone intarsia such as the one pictured here of "El Picaro' I have had to develop my own methods, so I experiment with ideas and try to contribute something to the hobby. Since I exhibit in other countries as well as all over the United States my intarsias must not be too heavy, they also hang in my home. The Florentine mosaics are heavy being backed with reinforced cement or possibly marble for strength. To get away from this weight problem I finally found the answer. My mosaics are fastened to a 1/8" sheet of aluminum making them light weight and structurally strong.

. . . . . . . . . . .

   Over the past nine years I have developed my own procedures for making a portrait. Using "El Picaro" to illustrate I will try to convey my progression from beginning to end.

An outline numbered drawing of the subject must first be made.

   First select your subject. If you can paint or draw so much the better, make your own original character. "El Picaro," (The Rascal) is an original water color based on the type of person I thought Poncho Villa might have been, cunning and shrewd. I tired to convey this feeling in the stone mosaic. The colors in the Sombrero were selected from materials I had on hand assuring me of a similar appearance. The same applied to the Serape, using the brightest colors I could find in gemstone. Skin tones are of shaded pieces of Bruno Canyon jasper purchased from Stewart's Gem shop in Boise, Idaho, a rather difficult item to come by since skin tones are exacting. Study your subject. I can't stress this too much. Decide where the joins in the material would be the least obvious in the finished mosaic. Follow along the dividing lines between light and shadow, lightly trace n the structural and contour lines of the face, cheekbones, chin, hair line, and eye brows. Important are the forehead lines, crowsfeet wrinkles around the eyes, dimples and the muscle line of a smile. These all give expression and modify your joins.
   Make as few lines on your drawing as your material will allow. These lines will define the separate segments of your master plan. Trace several copies and number each as illustrated in the master plan of "El Picaro," so you can easily identify the area in which you are working. Quite often a piece you have worked will prove unsuitable when fitted to other pieces and you will have to do it over again selecting more suitable material. This is the reason for extra patterns. Cut one sheet of the master plan apart like a jigsaw puzzle following the lines with a sharp stencil knife.

. . . . . . . . . . .

Figure 1 . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . Figure 2

Fig. 1: New Mexico wonder stone for a blended stripe in the serape.
Fig. 2: Sections used in the sombrero brim.

   Before gluing your pattern on the slices, study them. Look for natural markings that might simulate a wrinkle or vein, something that might eliminate a join or at least add to or improve the likeness you are trying to capture as well as cutting down working time. Figure number 1 shows patterns 316 and 317 marked out as one piece although each are of a different color after gluing each pattern over the selected portion of a slice with the numbers up, dry, then paint with clear shellac, proceed t the trim saw and then cut away unwanted material as illustrated in figures 3 and 4.
   You are now ready to grind each piece to the exact edge of the pattern, use a ½" x 6" wheel 120 or 220 grit whichever works best for you. Dress the periphery to fit the various curves. I use 3 wheels set up to give deep and shallow curves and on for straight lines. I seldom have to dress a wheel. The material which is usually 7 in hardness dresses as you grind if you do it correctly. The radius of your wheel will also give a slight bevel as you grind which allows for epoxy I the final gluing. When you begin to fit and assemble the shaped pieces you may find it necessary to make a new piece. This is why one makes more than one copy of he master plan.

. . . . . . . . . . .

Figure 3. . . . . . . . . . . . . ... . . . . . . . . . . . . . . . Figure 4

Fig. 3: Washington Jasper, showing how to trim saw cut into a deep curve in serape.
Fig. 4: Glue patterns on slices, rough out on trim saw.

   Sometimes it becomes necessary to subdivide because of a blemish in the chosen piece or if the shading is off color. In subdividing one can cut a blemish out and fit in a piece of the same slab, trying to use curved lines because straight ones are too noticeable, at least in the features of a portrait. The above is common procedure when doing portraiture, especially if one is striving for perfection, and it can be most frustrating so keep your cool and persevere. I had this problem of subdividing while working up "Heavenly Light." The only piece of jasper I had that matched the skin tones of the cheek had a freckle and the above method was used successfully. Matching skin tones can be very difficult so start with many slices preferably from one rock. I have worked for weeks trying to achieve certain effects and have not always succeeded.

Figure 5

Fig.5: Shape to an exact fit n a 6x half inch 120 grit wheel making a slight bevel toward the under side.

   Figure 5 showing patterns 193, 194, 195, were made for "El Picaro" but were a little to light to blend well with the rest of the face. The beautiful shading was hard to come by and it was with some reluctance that I discarded these and made new ones, after cutting many more slices. As one can see in the finished mosaic the many hours of extra work did pay off.
   When assembling the shaped pieces for fitting try putting them gently on a rolled out layer of children's play putty. The pieces stay put you can fit them. After working four or five pieces to your satisfaction clean thoroughly in lacquer thinner and place face down on a heavy sheet of glass covered with a tightly fitted sheet of polyethylene plastic. This stops the epoxy glue from sticking to the glass. Glue each piece in position and let sit for 24 hours. If you use a heat lamp to shorten the drying time the pieces should be covered with another piece of plastic and weighted down. Because these is a slight bevel on the gluing side and a heat light concentrates its heat in a central spot. The pieces will have a tendency to lift on the pouter edges unless weighted or taped down. This creates problems for the subsequent procedures.
   I work my entire project in small units of three to five segments, sometimes more depending on the pieces being assembled. Finally all units are put together and fitted once more using the same techniques as above. Let it set until completely dry.
   I try to cut all slices for intarsias one eight of an inch thick plus or minus 10 thousandths of a micrometer. This gives very little variation in thickness and leaves little space to fill with epoxy. For those of you who do come up with quite a variation try filling or leveling with plastic aluminum.
   Before polishing he intarsia it is mounted on a sheet of aluminum one-eight of an inch thick which is heavily scored on the glue side. Before mounting I drill and bolt on a hanger. This can also be put on using epoxy, after the portrait is polished. The intarsia is then epoxied to the aluminum sheet on the scored side. Tape the edges so the glue can't flow out and allow plenty of drying time.
   To polish, I set the intarsia into a block of plaster of Paris, making certain all parts are dead level, and that the plaster is considerable larger than the piece to be polished. Using a surface unit I proceed through the sanding and polishing as I would any large slab.
   The materials used in "El Picaro" were black jade, lapis lazuli, agate, chrysoprase, aventurine, jasper, agatized wood, rhyolite, wonderstone, and a black background of some type of crystallized hornblende - three hundred sixty four pieces on all, and four months work.
   Florentine mosaics are usually framed in polished marble; but this is up to the individual. Marble would be too heavy to conform to my needs. The making of gemstone intarsia or Florentine mosaic in its true form is fast becoming a lost art. This is especially true of portraiture. It is very gratifying to me to find the interest aroused in those attending the gem shows. I predict our future exhibits will prove our ability to revive this truly challenging art form.



back to top