roots (dry; no soil rests)

Large, interlocked root fragments were quickly precut with a classic scissors before the root fragments were fed. Afterwards, the sample pieces (mostly < 10 mm) were fed and ground within 15 seconds only. The grinding sound was indicating that the roots were not brittle enough to be ground by impact forces. Shearing off, between rotor and sieve ring was the main comminuting principle for this sample.

The grinding sound almost vanished instantly, after the last fragment was fed. We were able to brush out about 0,6 grams of ground sample material. Only a bit of fine sample dust was located below the rotor (between the first two channels of the labyrinth disk).

The perforations of the used 0,18 mm trapezoidal perforated sieve ring were not significantly clogged with sample. Surely even higher amounts of sample could be ground this way, too. Also the usage of a smaller perforated sieve ring might be plausible (see result 2).

For a rapid cleaning, the equipment was vacuumed with a soft brush. For a soft kind of sample and tiny amounts, also the usage of titanium equipment is plausible.

Also our Mini-Mill PULVERISETTE 23 can be used for a metal free grinding. For a metal free grinding, we recommend using equipment made of zirconium oxide. Because the sample was voluminous, we used a bowl of 15 ml total volume and two grinding balls of 15 mm diameter.

The mill was set to maximum speed (50 Hz) and 0,5 grams of sample were ground inside this bowl for a total grinding time of 10 minutes. A lot of root fragments were comminuted to a fine powder; only a few tiny fragments of roots were spotted.

Because the fine sample dust already started to stick slightly, we don’t recommend to proceed dry grinding this way. If a dry grinding is obligatory, eventually quartz sand can be added (in defined amount) to support rupturing the thicker root fibers quick enough, before fine sample dust will start sticking. Typically, a 1:1 mixture sand:sample mixture would be used. With moistened samples, even more of sand than sample material would be added.

For an intensive cleaning of the grinding parts, we filled about 3 grams of coarse sand about two grams of water and ground this mixture for two minutes. Afterwards, the equipment was flushed with fresh water and dried.