on Diamond Polishing
No lap creates
more fear and loathing than the Ceramic Lap. With the
same Mohs hardness as sapphire, ceramic laps are the hardest
polishing laps you can buy. Therefore, they create the flattest
polished facets of any lap.
particles become partially embedded into the surface of most
polishing laps. Ceramic laps operate differently, because all the
diamond particles remain loose on the surface of the lap. Since the
diamond stays on the surface of the lap, it is almost impossible to
have too little diamond on a ceramic lap. This makes loading ceramic
laps with diamond a challenge. Too much diamond is the most common
problem people have with ceramic laps.
One way to get
around this problem is to dilute your diamond spray. I learned the
following method from my friend Paul Head. He is able to polish just
about any material except quartz on his ceramic lap.
sprayer bottles at your local pharmacy that are the same size spray
diamond comes in. Put ½ teaspoon of well-shaken spray diamond
and ½ teaspoon of extender fluid into the spray bottle. Top off
the bottle with denatured or grain alcohol. This substantially
reduces the amount of diamond you will be applying to the lap with
If you are
starting off with a new ceramic lap, prepare it with a small amount
of graphite. Put about 1/8 teaspoon of powdered graphite into a spray
bottle and fill to the top with alcohol. Shake well and spray on to a
rotating lap. Immediately rub the graphite/alcohol mixture into the
lap and wipe off as much excess as possible.
Your lap is
now ready to receive diamond. While the lap is rotating at a slow
speed, spray your diluted diamond mixture on to the lap from about 10
inches away. Take a paper towel and rub the lap to evenly spread the
diamond over the lap. You will probably have too much diamond on your lap!
While the lap
is running slowly, very carefully place a razor blade at the center
of the lap. Press the blade into the lap with a light pressure and
slowly move it toward the outside edge of the lap. Be careful, razor
blades can be sharp. You still have too much diamond on your lap!
Get a clean
facial tissue or paper towel well dampened with alcohol. With the lap
rotating, start wiping the center of the lap and slowly move toward
the outside edge of the lap. Open up a fresh portion of your tissue,
re-wet it, and repeat the process. You are finally ready to start
polishing with your new ceramic lap.
discouraged if your new ceramic lap is slow in polishing. Ceramic
laps can take a long time to break in.
technique for setting up ceramic laps is rub tin/lead solder onto the
surface of the lap. Make sure that any oxidation on the solder is
cleaned off before loading the lap. The oxidation can create a
problem with contamination. Also make sure that your solder
doesnt have a flux core, because the flux can cause problems in
polishing. The thin tin/lead coating offers some help in reducing the
problem of your ceramic lap becoming overloaded with diamond.
pre-polish is a must with ceramic laps. Dont be surprised if
you have to cheat to get your facets to line up on your ceramic laps.
Ceramic laps tend to be the truest running laps available, so small
inaccuracies in your pre-polish lap will show up when you change over
to your ceramic lap for polishing. Some people get around this
problem by also using a ceramic lap for their pre-polish.
Keep your lap
clean and wipe it down with alcohol before using or changing to a new
tier of facets. I have found that best results are obtained with
light pressure and slow speed.
cant seem to get the excess diamond off your ceramic lap with
alcohol and a razor blade, (or if it gets contaminated) you can clean
it off with lava soap.
I only use my
ceramic lap for the hardest stones such as sapphire and chrysoberyl.
I find that the finicky quality of ceramic laps is too much of a
hassle on most stones. I cant say that Im a fan of my
ceramic lap, but I dont quite hate it either.