Articles

For starters, you need to prepare the surface of the lap before you can actually polish anything on it, because of the way it's made. You see, contrary to many popular beliefs, most "ceramic" laps aren't completely made of any one substance; they're made from two: a high-temperature glass binder, and Aluminum Oxide powder. (The latter provides the necessary durability and heat-dispersing capabilities, while the former seems to improve the chances of slicing the material into disks, square tiles, or whatever other shapes it's needed in.) As such, when you first receive your brand, spanking new ceramic lap, fresh out of the box, its surface may very well mimic those of any other well-sawn slab you've ever seen at a gem show: uneven, and just coarse enough to wreak holy terror on whatever newly-prepolished surface comes into contact with it. If you could see that pristinely innocent-looking lap's surface under extreme magnification, you'd see that it's porous, not solid, and that its "smooth" surface, as it comes to you, is actually more like a closely-packed "forest" of needle-like crystals, points faced upward and ready to greet your stone! (Hence, the need for the "preparation", which follows.)
To prep' your lap, you'll first need to invest $20-30 in a half-boule of Synthetic Sapphire (flame fusion variety), which'll serve double duty as both a preparation tool and a first stone to be cut. When it arrives, slice off enough from the narrow end to cut yourself a 10mm Round Brilliant, and then, with the curved side facing down onto the surface of your coarsest lap (so that you have the broadest possible "handle" to hold onto), grind a flat surface, about 1/2 as wide as the boule, itself. Once that's accomplished, scrub/wash off the surface of the boule and repeat the process on progressively finer and finer laps, until you've essentially created a thick slab of Syn. Sapphire that's easy to hold and easy to control, with one prepolished face on it.
Next, wash your hands and use a nail brush (to rid yourself of even the hint of a chance that you'll transfer stray grit onto your about-to-be-prepared lap), dry them and, with your ceramic lap mounted on your facetor, but standing still, pump 3-4 evenly-spaced shots of 100,000 mesh Diamond Spray onto the lap. If you're using Crystalite's isopropyl-and-oil-based pump spray botttles (which I vastly prefer over any and all others) DO NOT use any lubricant of any kind, at this point. Next, use your recently rewashed Syn. Sapph. burnishing block to smear the still-wet diamond spray in tight little circles all over the lap, so as to more or less evenly cover its surface from center to outer edge with a thin layer of the sprayed diamond compound.
A few seconds later, when the alcohol has dried, turn your facetor on, and set it to a moderate speed -- say, around 350 RPM -- and lightly touch your prepolished "burnisher" down onto the lap surface. You'll notice a "catching", or "dragging" sensation, as if the lap's trying to snatch the tool right out of your hands. Hang onto that Sapphire slab-burnisher, and occasionally pump a 1/2-spritz of more diamond spray onto the moving lap surface, until you feel the slipping-to-grabbing transition repeat itself a few times. That's the friction between the diamond and the two surfaces, as the isopropyl alcohol carrier evaporates, and the microscopic milling action continues. Since one of those surfaces is solid aluminum oxide, and the other's only a glass substrate containing AlO2 powder, the latter will eventually wear down flat, if you'll just bear with it long enough. In all, the breaking-in process shouldn't take you more than about ten or fifteen minutes.
Once you've reached the point where the surface of the ceramic lap has reached a sort of "slightly misty" prepolish -- sort of halfway between prepolish and polish, with a texture akin to the belly of a well-worn porcelain sink -- stop the lap, remove it from your machine, and go wash/scrub it off in your kitchen sink, using a good oil-reducing surfactant (the shampoo you use each morning's a great candidate), either a white or blue plastic 3M scrubber-sponge, and a healthy dose of elbow grease. The goal, here, is to completely remove all traces of the "old" grit and loose swarf from the breaking-in process, so that you're left with a squeaky-clean, relatively prepolished surface, ready for its next usage. That "misty" appearance you're after is, essentially, a polished, dead flat surface, with ample pores still accessible to the polishing compound particles. After it's been thoroughly scrubbed clean, let it air-dry in your dish draining rack.
With your now-prepped lap mounted back on the master platen and tightened in place, start it spinning again; this time, to about 500 RPM, if your machine'll accommodate that. Since the ceramic is such a delicate, brittle material, I prefer to start the rotation at a slower speed, then gradually ramp up to the intended polishing speed, "just to be on the safe side". (On my Ultra Tec, I generally polish somewhere between #'s 7-9, on the speed control dial.) Now, spray 2-3 pumps of that 100,000 mesh spray onto the lap and, using a doubled-over piece of tissue or paper towel (my preference runs toward 1" wide, torn-off strips of Bounty "Select-A-Size" towels) wrapped around your index fingertip, make one continuous sweep (with moderate pressure) from the center nut to the outer edge of the spinning lap, to remove excess diamond compound. As I do it, it's two rapid sprays followed by a 1-2 second swipe, all before the alcohol dries on the lap, and... "VOILA! Zee lap, she eez a-ready!"
Now -- assuming you've prepared a cut stone (preferable a Syn. Ruby or Sapphire) for polishing -- start by touching down about 1/2" shy of the lap's outer edge, and gently sweeping back and forth between there and a position about 1" from the lap nut. The idea is that you want to use the outer area, which is moving past the stone at a significantly greater surface-feet-per-minute speed than the center (and is therefore exposing the facet to more diamond compound) as the starting point, to get the polishing process underway, then move closer to the center, to finish up. Because you're not using any lubricant other than the little bit included in the carrying agent, you'll want to pay close attention to the heat buildup your stone is reaping, and make sure the stone is cool (so it doesn't melt the dop wax enough to slip).
My method for this is to keep a few of those aforementioned 1" wide, folded-in-half strips of "Bounty" and a spray bottle of Windex handy; after 1-3 seconds of polishing, I lift the stone up, swipe off the accumulated polishing compound and swarf with the Windexed paper towel swab, then gently blow on the newly cleaned, wet facet. As the Windex evaporates, it both gives me a good look at my progress and cools down the stone, simultaneously! If you'll just follow this procedure over and over again, and remember to use a gently scrubbing/"pencil erasing" motion with your hand on the stone, I promise you that you'll be able to generate astonishingly flat, well-polished facets, day-in and day-out, just as I have for the past eighteen years. Instead of all of that pressure (and those G-dawful shreiks from the lap), try using a lighter touch and a higher speed ...especially on your tables!