"Notes On Making Intarsias"
By Meredith Jones
Kitsap Mineral and Gem Society

Figure 5

   There are many details in this lapping process to be explained. I use a ¾-inch sheet of plywood for a turntable about 2½ feet in diameter. My intarsias are secured with wood screws through the plywood turntable and turned at about 250 r.p.m. with a ½ h.p. motor. The intarsia, being rectangular, should have temporary extension pieces added to the sides to allow lapping to the far corners. See Fig.5.
   The top pieces being lapped are held and controlled by a hinged arm of pipe or rod mounted on a pivot above and across the turntable. To each slab that is used as a lapping tool, bond a small section of ¾-inch plywood containing a 3/8-inch hole in its center. The hole will receive the pivot point on the cross arm and when the bottom lap revolves this top piece will also turn. Add grit and water as he cross arm is moved from side to side and the resulting grinding action is really terrific. Use downward pressure and continue applying grit and water until both pieces are lapped smooth and flat.
   Starting frit on most intarsias should not be courser than 220 as soft areas quickly eat away with course grit and leave hollow areas. From 220 progress to 500 and then 1200 grit.
   Polishing is very simple. A very high luster can be obtained by using a flat wad made of a wool rug n the same manner. Apply any good polishing agent such as tin or cerium oxide with water. I use red iron oxide (rouge) because it also polishes well and is very cheap but, unfortunately, also very dirty. It can stain some porous materials.
   The polishing operation normally runs at least an hour or two, although some material develops a high luster in ten minutes. Continuous attention is not necessary if the cross arm is secured in a fixed position and properly weighted. Check and keep the polishing pad moist by adding water at least every half hour until satisfied with the polish. The rug pad can cover the turntable with the work in the top position if the piece to be polished does not overhang the turntable.
   This may be confusing but I hope Fig. 5 will give a better picture of what I call upside down lapping.
   The lapping method can be used on practically l flat surfaces and some suggestions are in order. Small flat pieces can be laid face down on a sheet of glass and plaster poured over them to form a slab, which can then be lapped and polished….

A walnut table inset with petrified wood log sections and buffaloes made of patrified wood. White plastic forms rthe oval. The entire top is finished in clear plastic. A matching chest has the same design on both top and front. The log section is made from a wedge-shaped piece of petrified wood, cut into nine slices, and fitted to gether to form the finished circular slab. Made by Meredith Jones.

   Before writing this article I was asked to describe the methods I use which, no doubt, are not the same as those used by a lot of people. The thought behind the effort can be summed up by a recent remark of a friend, 'If I give you a dollar and you give me a dollar, we will both still have one dollar, but if I give you an idea and you give me an idea, we have both profited because now we have two ideas.' My hope is this article will make many fellow gem cutters just a little richer."



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