8000M Mixer/Mill
Page 13 of 27 SPEX SamplePrep LLC January 2010
5.1 Mixing and Grinding (Cont’d)
Avoid grinding small loads (less than 3 grams) in brittle containers such as alumina, agate,
zirconia, and silicon nitride. If there is not enough material to cushion the impact of the balls,
they will generate excess contamination and can in extreme cases chip the container.
CAUTION: Always use grinding balls that match the material of the container, e.g. steel balls
for a steel container, agate balls for an agate container, etc. This will limit
contamination. An inappropriate choice of balls, such as tungsten carbide balls in
an alumina container, can damage the container.
Two balls are standard for most grinding containers, though some users feel that only one ball
should be used in the most brittle containers (alumina and agate). Three balls can hasten
grinding in the strongest containers, the steel ones.
When using grinding containers with threaded aluminum caps (steel and tungsten carbide), be
careful to keep the threads clean. Over time, if care is not exercised to maintain the threads
clean, as sample accumulates in the threads it can jam the caps. Also be careful not to drop
these caps on edge, as if they are knocked out of round they can be very difficult to use.
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