6.4.5 Weight of the balls (type of material)
A higher mass (specific weight) of the grinding balls accelerates grinding.
(see table in
Chapter 6.1 „Choice of grinding bowls and grinding
6.4.6 Dry grinding
DANGER!
Dust explosion!
There is a risk of spontaneous combustion especially for
very fine metal oxides and a thus resulting dust explo-
sion. Mind the external temperature and the pressure
that can develop in the grinding bowl during the dry
grinding.
NOTICE!
Dry grindings need to be checked in briefer intervals.
Longer dry grindings, without pauses and checks, can
cause the grinding set to gum up and to become dam-
aged. In particular with agate, the grinding bowl and
grinding balls can become damaged after a short
grinding time.
At a particle size of less than 20 µm, the surface forces prevail. The
grinding stock begins to stick.
Additional dry comminution can be achieved by adding surface-active
substances to the material to be ground.
Examples (maximum amount to be added in mass %)
n
Stearic acid 2-3 %
n
Aerosil (fine-particle silicic acid) 0.5 - 2 %
n
Quartz sand ~ 2 %
n
Glass powder ~ 2 %
n
Glycol (Ethylene glycol) ~ 0.1 - 0.5 % (
≙
5 - 25 droplets)
n
Triethanolamine ~ 0.1 - 0.5 %
Using the device
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