Bremen green

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Bremer Grün , also Bremer Blau , is a green-blue color pigment made of copper (II) hydroxide (copper oxide hydrate, Cu (OH) 2 ), which was invented in Bremen and was popular in the late 18th and 19th centuries .

history

The inventor of the Bremen dyer, merchant and manufacturer Nicolaus Kulenkamp the Elder (1710–1793), who, in addition to soaps and tallow products, had been producing this color since 1778, was soon copied by other manufacturers in Bremen. By 1807 at the latest, when there were four such companies here, called “Bremer-Grün-Fabriken”, the designation of origin had also firmly established itself nationwide. It has also been lexically comprehensible since the middle of the century. Minden, Kassel and Eisenach were named as other production locations. Despite its toxicity, paint was still widely traded and used beyond the turn of the 20th century.

Manufacturing

Copper (II) hydroxide

Kulenkamp's recipes have apparently not been passed down, a description from 1856 of the various, slightly different production methods is quoted, others can be found in detail in the links below:

“For the production, which is operated especially in Bremen, also in Minden Kassel, Eisenach etc., one uses table salt, copper vitriol and the like. Copper sheet. The first two, in fairly equal parts by weight, are ground to a homogeneous, thick paste with the addition of a little water. To this pulp there is half the weight of the same quantity of old copper sheet cut into small pieces, and the like. so that a layer of paste 1 ⁄ 2 inch thick alternates with a layer of sheet metal. The whole thing stays for about 3 months in the oak, not iron-shod oxidation tub and the like. is shoveled over with a copper shovel at least once a week during the time to promote oxidation. Then the mass is diluted with water, freed from the residue of the copper sheet and. filtered. The sludge obtained is first treated with hydrochloric acid, then after 36 hours in another vat, the blue baking, with colorless caustic potash solution, which completely decomposes the green basic hydrochloric acid copper oxide and the like. is transformed into copper oxide hydrate with the peculiarly greenish blue color. The color washed out with water is squeezed out in a filter bag, the soft mass is cut into pieces and the like. lets these air dry. "

- Pierer's Universal Lexicon . Volume 3. Altenburg 1857, pp. 273-274.

Processes deviating from this were also described as Bremer Grün , so in 1835 copper vitriol and nitric acid were recommended as starting materials for this process. Like other copper compounds, copper oxide hydrate is sensitive to hydrogen sulfide and sulfur dioxide.

Bremen green was used as a blue lime paint and as a glue paint; as an oil paint, it takes on an intense green within 24 hours.

See also

Web links

Individual evidence

  1. ↑ Heinz Schlecker: The three times award-winning Kulenkamp . In: Bremisches Jahrbuch 37, 1937, p. 84.
  2. ↑ Christian Abraham Heineken : History of the Free Hanseatic City of Bremen from the middle of the 18th century to the French era [1812], Bremen 1983, p. 151.
  3. ↑ Annals of Pharmacy . Volume 16, 1835, p. 239, see link Bremer Grün after Bley .