Bones (dry without marrow)

For our first trial, we used desired Cross Beater Mill PULVERISETTE 16. The mill was set to 4000 rpm (maximum speed) and a batch of 100 grams of sample (A) was slowly fed into the grinding chamber.

The grinding sound was typical and we finished feeding after ~ 40 seconds. During the grinding process, some dust escaped the filter house and was removed by a vacuum cleaner which was hold next to the mill. After 80 seconds, the grinding sound vanished.

We opened the grinding chamber; ribs and rotor were only slightly polluted. Surely higher amounts of sample could be ground this way. A bit of ground sample remained below the grinding insert and could be brushed off rapidly to maximize the output. Without brushing out, we found almost 84 grams of ground sample material inside the collecting vessel.

For our second trial, we used the Disk Mill PULVERISETTE 13 (premium line). This type of mill can also be used for metal free grinding (with zirconium oxide grinding disks). Few bone samples were ground successfully, but those were bleached and dried before the samples were ground.

We prepared a batch of 100 grams of sample A and slowly fed the sample into the grinding chamber. The sound of grinding was typical, but vanished only slowly. We interrupted the grinding process after a total grinding time of five minutes. The output which passed the gap of 0,35 mm was up to ~ 3 mm long. Only the half of sample was comminuted properly after five minutes.

We aborted the trial at this moment, the output was much too big and required grinding time would be way too long for effective comminution.

Finally, 105 grams of sample B were used for comminution with our Universal Cutting Mill PULVERISETTE 19. The start size is sufficient to use the funnel for long and bulk solids. Our protected funnel with sample pusher is only needed, when the diameter of sample would be > 3 cm.

We recommend knives made of hardmetal tungsten carbide for a much longer durability. The sample was fed with moderate speed. Grinding sound was typical and the fragments of bone were not too large.

All fragments were fed within 30 seconds and we switched off the mill after 40 seconds (with almost no more grinding sound recognized). There was no significant dust formation observed during this trial. After 10 more seconds of grinding, no additional output was found inside the used 3-liters collecting vessel. Because of this, 40 seconds would be sufficient; we determined an output of 100 grams which is typical (3- 5 of residues are usually found inside the grinding chamber). The trapezoidal perforations were almost free, also no significant residues are left on the rotor. Surely higher amounts of sample could be ground this way, too.

Cleaning was performed rapidly by vacuuming with a soft brush.