Shark Teeth

Basically our Mortar Grinder PULVERISETTE 2 is the most sensitive mill and slowly reduces the size of particles. Also the temperature of sample remains low when the sample will be ground with a mortar.

To furtherly improve the output, we would recommend to sieve out desired fraction in short intervals (e.g. every five minutes of grinding).

We used the desired amount of sample and slowly fed the teeth into the mill by the small opening inside the lid. The scraper was lifted in order not to block the large teeth we fed into the mill.

The grinding sound was relatively harsh and the lid of the mill (where the pestle was attached) was moving left and right. This indicates a harder sample and can become problematic when higher numbers of batches will be ground on a regular basis.

We aborted the trail after one minute. Only a few small fragments were formed. The grinding set was cleaned by comminution of a small quantity of sand and water for about five minutes. Afterwards, the grinding set was washed with fresh water and dried.

For our trail, we programmed a grinding time of 30 seconds only and separated the desired fraction by sieving after each step. At maximum speed, we already sieved out ~ 6 grams of sample which passed the 1 mm test sieve.

After a complete minute of grinding, only 8 grams of sample was fed back into the bowl. The fineness improved and only four grams of sample were placed back into the bowl after 1,5 minutes. We aborted our grinding trial after two minutes of total grinding time and a residue on top of the test sieve of 3 grams. A few of the junks appear to be too large for a comminution with 20 mm Ø grinding balls. Such fragments could be pre crushed manually (e.g. inside of a plastic bag with a few strokes of a hammer), or more of sample could be used (min. 30 ml of bulk sample) with our 250 ml grinding bowls when 30 mm Ø grinding balls will be used.

We packed the ground fraction < 1 mm and coarse fraction > 1 mm into separate plastic bags for demonstration. The grinding equipment was cleaned intensively by comminution of a small portion of sand and water. After about two minutes of grinding time, we flushed the equipment with fresh water and dried it off afterwards.