Ashes (with wooden pieces and metal fragments)

Sample starts to stick after only 2 minutes. This happens usually after the majority of particles reached a fineness of < 20-30 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and just become compressed by the used grinding balls. These clusters of particles also contain bigger particles which will not be ground any further too.

To proceed dry grinding, we sieved the complete sample with our Vibratory Sieve Shaker ANALYSETTE 3 Pro and a test sieve with 200 µm mesh. Only coarse fraction has been fed back into the bowl and proceed grinding until sticking occurs again.

This procedure has been repeated after totally 4 minutes again. After the 5th minute, grinding has been aborted because of sticking.

With our last sieving step, only a few wooden pieces have been found on top of the used sieve. Also a few metal fragments (lightly deformed by the grinding balls) have been found too. Probably it has been pieces of nails before the wood got carbonized.

The second sample has been proceeded analogous to result 1; sticking occurred only after 5 minutes; a 100µm mesh test sieve has been used to separate fine fraction and proceed grinding coarse fraction (only 1 sieving step in between).