FRITSCH PULVERISETTE 7 premium line - Manual (Page 38)

5.6.5 Weight of the balls (type of material)
A higher mass (specific weight) of the grinding balls accelerates grinding.
(see table in Ä Chapter 5.2 ‘Choice of grinding bowls and grinding balls’
on page 31).
5.7 Dry grinding
Below a particle size of approx. 20 µm, the surface forces prevail and the
material to be ground starts 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%
5.8 Wet grinding (grinding in a suspension)
DANGER!
Explosion hazard! Ignition hazard!
The device is not explosion-protected. If flammable liquids
are used, make sure that the heat developing in the
grinding bowl does not reach the solvent's boiling point.
Program appropriate cooling phases. If the vapour pressure
is too high, vapours may escape and ignite.
If it can be avoided, we recommend using non-flammable
liquids or liquids with a high boiling point. The boiling point
should be above 80 °C and above 100 °C for a long grinding
duration.
During the transition to grinding in suspension, you can add a liquid aux-
iliary agent with high boiling point and low vapour pressure, e.g. water,
white spirits (boiling point 100 - 140°C), or alcohols with a high boiling
point (e.g. isopropanol)
We recommend that you only use so much liquid that the suspension
has the same consistency as motor oil. With this viscosity the best results
can be achieved in most cases.
Using the device
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