John, the following vibratory tumbling instructions were taken from
the Lapidary Digest. Hale Sweeny, the list father, moderator and
guru, allows non-commercial reprints. Since these instructions were
not for a Mini-Sonic, you may have to modify them a bit.
The three tubs are not necessarily for different grits. The tubs can
be used to process stones of different hardness at the same time, or
one can be saved for just doing final polish. Warn your student that
putting soft rocks with hard ones will result in quickly turning the
soft rocks to mud. Obsidian (about 5 1/2 hardness) tumbled with agate
(about 7 hardness) will almost dissolve. Thus the value of having more
than one tub.
Vibrating tumblers work quickly and must be checked at least a couple
of times per day so the stones don’t dry out.
There are several polishes which can be used for tumbling. All of
them can be enhanced by adding a half teaspoon of Linde A or the
generic equivalent (3 micron sapphire powder). Doing this can help
the stones achieve a mirror finish.
For more help, look at the Lapidary Digest archives. There are
several threads which focus on tumbling, especially the last stages of
VIBRA SONIC TUMBLING INSTRUCTIONS
GRINDING and POLISHING SUGGESTIONS
(1) COARSE GRIND: Fill bowl to within about 1 inch of top with washed,
well drained rocks. Add 1/4 cup coarse silicon carbide (200-250
grit), and 1/4 to 1/3 cup water with 1/4 teaspoon detergent, (Tide,
Cheer, etc.). Run at high speed for 24 to 30 hours. As mud builds up
from grinding, more water should be added (about 2 or 3 tablespoons).
Wash and repeat coarse grind until desired grind is attained.
WASH THOROUGHLY AND DRAIN. Washing is best accomplished by the
1 . Turn off unit.
Remove pulley cover and change belt to low speed position.
Replace pulley cover.
Remove and wash bowl cover, add 1 or 2 cups of water and add
about a tablespoon of detergent to rocks in bowl.
Replace cover and operate at reduced speed for a few minutes. Do
not allow liquid to spill over onto motor or bearings.
Turn off unit and pour rocks into collander or similar straining
device. Run cold water over rocks while stirring them with your
Repeat foregoing procedure.
NOTE: It is wise to eliminate stones which are very porous or ones
which have deep cavities so that coarser grits will not be
carried over into finer grinding phases.
(2) FINE GRIND: To the coarse ground rocks, add 1/4 cup fine
(500-600 grit), silicon carbide, 1/4 to 1/3 cup water with 1/2
level teaspoon detergent. Run low speed 2 to 3 days or until
rocks have velvety sheen surface. Again a very small amount of
water will be required.
WASH THOROUGHLY AND DRAIN
(3) PREPOLISH: After fine grinding and washing, rocks should be
examined closely to be sure there are no cracks or pits
containing grit from grinding. if so, remove them from the load and
scrub the spots free of grit. Rinse again thoroughly, drain well
and add about 1/4 cup Levigated Alumina and 1/4 cup water.
Run low speed 2 to 3 days. Rocks should now show a definite semigloss.
WASH THOROUGHLY AND DRAIN
(4) POLISH: To the semi-polished rocks add 1/8 to 1/4 cup tin
oxide and 1/4 to 1/3 cup water and 1 level teaspoon
detergent. Run low speed until polish is attained, 3 or 4 days. Save
the tin oxide slurry, as it may be used several times (if it is
kept clean and free of grit). After tin oxide polish, a few hours run
(3 or 4) at low speed in about 1 cup water with 4 or 5 teaspoons
detergent will enhance the gloss. NOTE: As Gy-Roc grinding is
extremely fast it is essential that a minimum amount of water
be used, yet care must be taken that the mass does not run dry. It
should be looked at every 6 or 8 hours and if the mud looks thick
a little water (2 or 3 tablespoons) should be added.
WARNING: DO NOT USE EXCESSIVE AMOUNT OF WATER, AS IT COULD CAUSE
SPLASHING, RESULTING IN RUINED BEARINGS AND BURNED OUT MOTOR. BE SURE
THE LID IS SNAPPED ON TIGHT.