garnet

Start size is suitable for a direct grinding with the Mortar Grinder. With a downforce of 9 daN, sample starts sticking lightly after 30 minutes of grinding.

This uses to happen after the majority of particles reached a fineness of < 30 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and become compressed by the pestle. These clusters of particles also contain bigger particles which will not be ground any further.

We checked the present fineness by using a Laser Particle Sizer ANALYSETTE 22 Compact. Already d90 < 48 µm has been determined. For this, desired fineness is achieved. Probably 20 minutes might be fulfilling too.

If sample starts sticking and a better fineness is required, still grinding in suspension is possible to improve the grinding result.