Hair

The present hair sample had shown a length about 30-40 mm which should be too long for a direct feeding into the grinding bowls. The hair should be < 20 mm long to fit without problems. It is also possible to bend the sample into the bowls.

We used a 10 ml bowl made of zirconium oxide and 3x 10 mm Ø grinding balls to comminute the 0,35 grams of hair sample. The hair was filled into the lower half and we added the grinding balls on top. With the top half of the bowl, the too long hair fragments were bent into the bowl, a precutting was not required this way.

After the first 5 minutes of grinding with 50 Hz (max. speed), we emptied the bowl. In case that a few hair fragments were clamped between the half’s, this way, all hair should become ground successfully. We found a lot of present dust, combined with a majority of fragments of hair with ~ 5-10 mm length.

The sample was placed back into the bowl and we ground the complete sample for further 10 minutes (15 minutes of total grinding time). The majority of the hair was comminuted to < 100 µm. The sample was lightly sticking on the inside of the bowl. This was typically happening when a d50 < 20 µm was reached.

For an intensive cleaning of the grinding equipment, we ground a small portion of sand with a few droplets of water for 2 minutes. The abrasive sand is removing residues and the equipment only required a flushing with fresh water and drying off.