On Making Intarsias"
By Meredith Jones
Kitsap Mineral and Gem Society
After your picture is drawn with all cutting lines
indicated, make a duplicate with carbon paper, on thin hard cardboard or
template paper. The master picture should then be mounted on a board and
covered with a sheet of plastic. This will become your working model to
check each piece before cementing. The cardboard carbon copy can be cut
out, a piece at a time, for individual templates.
The slab material can vary in thickness but approximately
3/16 inch is ideal. Thicker material is harder to cut and shape while thinner
material may lack sufficient strength. Cementing is done face down on a
piece of wax paper resting on a sheet of glass. The wax paper must be thin
and free of dirt or wrinkles. The surface of the picture is thus kept true
and flat while the back can vary without harm.
The picture is completely assembled piece by piece,
before being bonded to a board to give it strength. A good adhesive must
be used and epoxy resin is excellent for this purpose. A patch of glass
cloth may be added here and there to strengthen the back during assembly.
took 1077 pieces of petrified wood, agate, and jasper to make this 33-inch
diameter table. The intarsia technique was uswed. There is no plastic embedment.
The top is lapped and polished. Made by Meredith Jones.
The largest project I have attempted in this manner
was a 33-inch tabletop with 1077 pieces. The entire section, before it was
bonded to a three-quarter inch sheet of plywood, appeared to have the approximate
strength and thickness of plate glass.
During the construction period the project is handled continually. Each
piece is fitted face up and then turned over for cementing. One slip or
bump could spell disaster.
People marvel at the many fine lines and delicate pieces
and wonder how it is possible to cut and fit such small objects. The answer
is rather simple and I will try to explain by referring to a map of the
The Columbia River, for instance, is the boundary between
Washington and Oregon. It is wide at the mouth, tapers upstream and is crooked.
The river can be added by using a piece of green rock. First cut and shape
the State of Washington. Next fit a large piece of the green rock all along
the south side of Washington, where you want the river. The Washington piece
can be laid on the green slab and a perfect cutting line scribed with a
thin aluminum marker. Now cut and grind the green slab to fit against Washington
and cement the two pieces together. When the cement is set, trim saw the
surplus green rock way (it may have extended clear to what would be the
California border of beyond). Now grind the south bank of the Columbia River
to suit you. It may be a quarter inch at the mouth and as thin as this paper
before reaching upstream to Pasco.
Note - the Columbia River must be added to the State
of Washington while it is a separate unit. If the Washington piece had been
cemented to Idaho or any other large section of the intarsia, the trim sawing
and grinding of the river would be very difficult.
Oregon is next. This can be completely shaped on three
sides, being sure to leave some excess material on the California side.
Be sure to fit carefully to the Columbia River side before cutting the California
border. The reason is obvious. In getting a good fit along the river, more
material than anticipated may be cut away and the surplus material on the
California side may be sorely needed. The composite Washington-Columbia
River piece can be used as a template to mark the northern edge of Oregon.
By using the above process, i.e., attaching detail
pieces to a major piece on one side and then finishing the other side, flower
stems, tiny bird bills or claws, and similar details can be shaped on a
common, ordinary grinder and trim saw.
Speaking of trim saws, a few comments are in order.
My eight-inch blade extends four inches above the saw table. By holding
a slab firmly in both hands and passing it across the face of the blade
a cut can be made the full length, about 1/8-inch deep. The remaining portion
can be broken by hand. The usual method of passing the edge of your slabs
directly into the blade not only means more material has to be removed by
cutting but the scraping action can destroy the diamond edge. By passing
the material across the blade instead of directly into it, the blade life
can be doubled and material cut much faster.
With practice a great deal of accuracy can be developed
but if you allow your work to twist and turn, the blade will grab. To prevent
this, hold the near end of your slab down against the flat saw table and
lean the top edge against the blade. As cutting progresses, slide the bottom
of the slab toward the blade in a sort of upward rolling motion. Of course,
some material, such as long, narrow strips, should be cut completely through
in the conventional manner.