Pigment processing: The isolation of the naturally beautiful

The 1977 founded company is managed by chemist Dr. Georg Kremer. The core of the business is the preparation of pigments according to ancient formulations. By comminution of the raw materials like for example minerals or plants, which are required by the recipe, the pigment is identically reproduced. The experience and reports of the users have shown, that the synthetic alternatives do not come even close to the quality of the original formulations. Therefore customers gladly use Kremer's supply of pigments. Kremer's customer base consists of artists and restorers from around the world ^[1].

A pigment which is being comminuted has an altered colour, in contrast to the primary particle. This is due to the fact, that crystals because of their size, influence the transparency. The primary particle is therefore responsible of how we optically perceive it. Shown in the photo on the right, the intensity decreases towards the left – to the finer particles; therefore the finest share seems to be the lightest. The shares are: < 63 µm, 63 – 80 µm, 80 – 100 µm, 100 – 125 µm, 125 – 200 µm.

At Kremer's pigments, various FRITSCH laboratory mills are utilized. The Jaw Crusher  PULVERISETTE 1 classic line is used for the coarse pre-comminution, large amounts can be excellently continuously ground. For the additional processing, is the Disk Mill PULVERISETTE 13 classic line the suitable instrument. The material characteristics of the sample decisively influence the choice of the comminution method.

For brittle or fibrous materials the staff of Kremer's pigments has the Variable Speed Rotor Mill PULVERISETTE 14 classic line available. Here the rotor precisely comminutes the rough pieces and only discharges the suitable share through the sieve into the collection vessel. But also the Mortar Grinder PULVERISETTE 2, as well the Planetary Mill PULVERISETTE 5 classic line are used. The Heavy Duty Analytical Sieve Shaker ANALYSETTE 18 is utilized for the subsequent fractioning.

The essence of pigment processing with the FRITSCH Planetary Ball Mill is that the particles obtain a softer almost round shape through the circulation inside the grinding bowl and the mechanical strain of the round grinding bodies. Of course it would be ideal if the desired grain size distribution of the particles could be very closely together. Very often the production of pigments of a certain fractions is requested. For this reason the grinding parameters at Kremer's were optimized in order to avoid the production of too many large or fine shares and producing as much as possible of the desired fraction.