In the art world, it is fostered by an incessant rain of numbers in the media whenever an art star comes to its attention. Graffiti Artists Turn on Banksy: The Rise of Art Hate Anthony Haden-Guest August 6, 2014
For the music genre, see Sludge metal. Sludge. Sludge is a semi-solid slurry and can be produced as sewage sludge from wastewater treatment processes or as a settled suspension obtained from conventional drinking water treatment and numerous other industrial processes.
Sludge is caused by quench oil thermal and oxidative degradation. The oxidation reactions lead to polymerized and cross-linked molecules, which are insoluble in the oil. The relative amount of sludge in quench oil may be quantified by the precipitation number.