"Discovering A Lost Art Form"
by Conrad Grundke

Learning Commesso, Part I


   Since commesso/intarsia is a relatively unknown art form, Part I of assembling the picture "Mountain Retreat", will discuss some general tips and techniques for making a commesso/intarsia. You will want to keep these in mind when you begin to assemble the picture in Part II. You can also refer bafck to them as you move on to more challenging commesso/intarsia projects.

Tips & Techniques:
   The following tips should be considered when selecting, cutting and fitting the pieces in an intricate "Commesso."

1. Picture selection
   a. Not all pictures lend themselves to becoming "Commessi/Intarsias." With experience one can predict the difficulty a picture will present and this is best developed by starting with simple "Intarsias," like the one in this article, and then progress to more difficult ones with time.
   b. Required colors and textures may dictate the picture selection. Bright yellows, blues and reds are difficult to find and the picture may not have the impact desired when the compromise is made with stones having duller colors.
   c. Larger pictures will stress the stone selection because larger pieces are needed. These are not always easy to obtain. Smaller pictures reduce the need for larger slabs, however, smaller pictures require more precise fitting. You must weigh these two options.


Scanning the stone patterns into a computer and manipulating them can give the artist an idea of how the finished piece will look.

2. Picture Generation Using PC:
   a. I have found that my Personal Computer has made a major impact in the way I select my picture, stones and templates. After generating a line drawing by either tracing or freehand drawing, I scan the image into my computer and create an Adobe Photoshop file from which I can manipulate the working drawings.
   b. Using the image/image size options I can generate any size picture up to 8 ½" x 11" and make as many copies as needed using my printer.
   c. One question that is always difficult to answer, is, "How will my picture look with the rocks that I have selected?" If you started with a colored picture and you can select rocks that exactly match the original color and texture, you already know. In most cases, the rocks you select will vary considerably from the original.
   d. Once I select my slabs, I place the individual slabs on my scanner (with special care to not scratch the scanner glass) and scan the image into my computer. Again I put it into an Adobe Photoshop file and by selecting an area of the slab I can "Edit/Define Pattern" to store that color and pattern onto my hard drive.
   e. Using the line drawing in Adobe Photoshop, I then select the area where that slab is to be used using the "Magic Wand Tool."
   f. Once the area is selected, I then "Edit/Fill/Pattern" using the selected pattern, which is the slab I have selected for that area, and then fill the area with the actual rock pattern.
   g. Repeating this process for each of the different sections, I can create a colored rendition of the final picture with a very close approximation to the color and pattern of the selected stones. Using this technique it is easy to try different slabs and patterns for the final desired effect. Fig 1 is a computer-generated picture using this process.

3. Stone selection:
   a. The most critical part of a picture is the selection of the proper stones. This is the one area that cannot be compromised. A viewer's mind will forgive inaccurate fitting of the pieces, but the mind will not replace inadequate stone selection for either color or texture. Pattern and color are very important. Each stone must closely resemble the object it represents (i.e., sky, stone wall, leaves, grass, etc.) in order for the picture to look right. Also pay attention to light and shade, using slightly darker material for the areas in shade. You may go through many pounds of rock before finding just the right ones.
   b. Never start a "Commesso/Intarsia" until you have selected all the stones needed for the picture. Not having the proper stones to start with will result in inserting what might be available rather than what is needed when the time comes.
   c. Whether you purchase slabs or cut your own, try to make them of approximately the same thickness to avoid having gross variation on the back. Slabs 1/8-5/16" thickness will be most common with ¼" preferred.
   d. In Italy a Commesso/Intarsia Pietre Dure is comprised of stones of the same approximate hardness. We do not have that luxury and many areas of the country will find certain colors hard to find. In California, white stone is generally Howlite with a hardness of 4.5. Most Howlite will not take a high polish and the resultant completed picture will be finished to the best polish of the least polishable stone, quite often in our case Howlite.
   e. As a Commesso/Intarsia ages, many stones will change color due to viewer handling, cigarette smoke, and various oils and chemicals in the atmosphere. The harder the stone, the less likely that they will change color, although many pieces of rose quartz will fade drastically over time. To circumvent this effect, I use an automobile wax to protect the picture when it is completed. Carnauba Wax is my preference. In the past we had used a Krylon spray matte finish. This does yellow and peel over time.

4. Suggested Possible Stones:
   a. Sky (#21) - Norwegian Sunset Marble
   b. Trees (#12 & 20) - Birds Eye Serpentine
   c. Tree (#10) - Brecciated Red Jasper
   d. Bushes (#13) - Agate
   e. Wall (#11) - Rhodenite
   f. Grass (#14 & #17) - Mallachite/Azurite
   g. Road (#15) - Picture Jasper, w/o the picture
   h. Wall (#16) - Brecciated Jasper
   i. Shady Mountain Side (#9 & # 18) - Howlite, very dark piece with mostly matrix
   j. Sunny Mountain Side (#19) - Howlite, light piece with slight matrix
   k. Bushes (#17 & #17a) - Red area from Pidgeon Blood Agate
   l. Sunny Steeple Roof (#2 & #6a) - Light Red Jasper
   m. Shady Steeple Roof (#6b) - Dark Red Jasper
   n. Roof Eave (#3c) - Black Basalt
   o. Sunny Steeple & Church Wall (#1 & #5) - Slate
   p. Shady Steeple & Church Wall (#3 & #5a) - Petrified Wood
   q. Windows (#1a, #1b, #3a, & #3b) - Abalone Shell or Paua Shell
   r. Steeple Tip (#21a) - Basalt


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