Granulate
As granulating or fill for (to lat. Granum , "grain", "graining") refers to the change from either large particles or of very small particles with different particle size ( powder ) in an agglomerate with particles of a narrow particle size. Granulating is a technique that is used in many areas and always serves to be able to process the substance better.
Procedure
Granulating in goldsmithing
For this purpose, z. B. Molten metal either in a thin stream in cold water with constant stirring of the water or with a wet brush held over the water and constantly shaken.
Easily fusible metals such as tin or zinc are poured into a box that has been heavily streaked with chalk on the inside , put on a precisely closing lid that has also been streaked out and shaken until the metal has cooled. Larger amounts are granulated in a rotating drum ( granulating machine ). This creates perfect spheres. If only a few spheres are required, they can also be produced individually from very small metal chips, as they contract into a small sphere due to the surface tension during melting. In contrast to the granulate balls produced in the above-mentioned technique, however, the bearing surface remains flattened.
Phosphorus is granulated by shaking it in a bottle half-filled with warm water and closed until it has solidified.
Cement manufacture
During cement production in granulating drums, granules (balls) are turned from ground lime and aggregates with the addition of water, which are then ground to cement after a firing process in rotary kilns.
Granulating in pharmacy
In the pharmaceutical industry, granulates are mainly used for further processing, for example for the production of tablets or for filling capsules . Wet granulation is often used, in which a solid is slurried and this moist material is then crushed (for example through sieves) and dried. Another method is dry granulation or roller compacting , in which powder is driven through a gap between two rollers. The resulting scabs are then crushed again on a sieve. Furthermore, there is fluidized bed granulation, in which water is added to a powder that is located on an air bed.
See also: granules
Spice production
When producing granulated spices, mainly onions and garlic, the products are first peeled and cut. After drying, the products are ground in order to obtain the seasoning granules.
Applications
In the granulation technique, especially in the production of gold jewelry, very small gold spheres with a diameter of approx. 0.3 mm, sorted by size, are applied individually in ornaments to the surface of the piece of jewelry without melting together. The Etruscans mastered this difficult technique to perfection . Later it was forgotten. In the 20th century, the old techniques were reproduced through experimental research and are used again today.
literature
- Erhard Brepohl : Theory and Practice of the Goldsmith. Fachbuchverlag Leipzig, seventh, improved edition, 1984
- Jochem Wolters: The gold and silversmith. Volume 1, materials and materials. Rühle Diebener Verlag Stuttgart, second, reviewed edition 1984
Web links
- Art of the Etruscans at museumonline.de with a photo of a granulated Etruscan work ( Memento from June 13, 2008 in the Internet Archive )
- Website of the goldsmith Johannes Lais with a description of the granulation technique and detailed photos of modern granulated jewelry
Individual evidence
- ↑ Ground, crushed, granulated - what is it? | Ostmann spices . In: Ostmann.de . April 20, 2017 ( ostmann.de [accessed July 6, 2018]).