{{Short description|Dye extracted from certain lichens}} [[File:Vitt yllegarn växtfärgat med orselj från lav.jpg|thumb|White wool yarn dyed with "orchella weeds", using traditional plant dye methods.]] '''Orcein''', also called '''archil''', '''orchil''', '''lacmus''' and '''C.I. Natural Red 28 - CICN 758600''', is any dye extracted from several species of lichen, commonly known as "orchella weeds", found in various parts of the world. A major source is the archil lichen, ''Roccella tinctoria''.<ref name="StClair">{{Cite book|title=The Secret Lives of Colour|last=St. Clair|first=Kassia|publisher=John Murray|year=2016|isbn=9781473630819|location=London|page=165|oclc=936144129}}</ref> Orcinol is extracted from such lichens. It is then converted to orcein by ammonia and air. In traditional dye-making methods, urine was used as the ammonia source. If the conversion is carried out in the presence of potassium carbonate, calcium hydroxide, and calcium sulfate (in the form of potash, lime, and gypsum in traditional dye-making methods), the result is litmus, a more complex molecule.<ref>{{Cite journal| doi = 10.1080/10520290410001671362| volume = 78| issue = 6| pages = 289–302| last = Beecken| first = H| author2 = E-M Gottschalk| author3 = U v Gizycki| display-authors = etal| title = Orcein and litmus| journal = Biotechnic & Histochemistry| date = 2003| pmid = 15473576| s2cid = 41944320}}</ref> The manufacture was described by Cocq in 1812 <ref>Cocq M. (1812). Mémoire sur la fabrication et l'emploi de l'orseille. ''Annales de Chimie'' 81:258–278. Cited in: Chevreul ME. (1830). ''[https://archive.org/details/leonsdechimiea02chev Leçons de chimie appliquée à la teinture]''. Paris: Pichon et Didier. p 114–116.</ref> and in the UK in 1874.<ref>{{cite journal | last1 = Workman | first1 = A Leeds | year = 1874 | title = Manufacture of Archil and Cudbear | url = https://books.google.com/books?id=NAYAAAAAMAAJ&pg=RA1-PA143 | journal = Chemical News | volume = 30 | issue = 173| page = 143 }}</ref> Edmund Roberts noted orchilla as a principal export of the Cape Verde islands, superior to the same kind of "moss" found in Italy or the Canary Islands, that in 1832 was yielding an annual revenue of $200,000.<ref name = "Roberts">{{cite book |last= Roberts|first= Edmund |author-link= Edmund Roberts (diplomat) |title= Embassy to the Eastern courts of Cochin-China, Siam, and Muscat : in the U. S. sloop-of-war Peacock ... during the years 1832-3-4 |url=https://archive.org/details/embassytoeaster00unkngoog |date= <!-- Digitized --> 12 October 2007 |orig-year= First published in 1837 |publisher= Harper & brothers |oclc= 12212199}}</ref>{{rp|pp.14,15}} Commercial archil is either a powder (called cudbear) or a paste. It is red in acidic pH and blue in alkaline pH.
== History and uses == [[File:Chromosomes of Allium ascalonicum.jpg|thumb|Chromosomes of ''Allium ascalonicum'' stained with orcein]] The chemical components of orcein were elucidated only in the 1950s by Hans Musso.<ref>{{cite journal | last1 = Musso | first1 = H | year = 1960 | title = Orcein- und Lackmusfarbstoffe: Konstitutionsermittlung und Konstitutionsbeweis durch die Synthese. (Orcein and litmus pigments: constitutional elucidation and constitutional proof by synthesis.) | journal = Planta Medica | volume = 8 | issue = 4| pages = 431–446 | doi = 10.1055/s-0028-1101580 | s2cid = 85077252 }}</ref> The structures are shown below. A paper originally published in 1961, embodying most of Musso's work on components of orcein and litmus, was translated into English and published in 2003<ref>{{cite journal | last1 = Beecken | first1 = H | last2 = Gottschalk | first2 = EM | last3 = von Gizycki | first3 = U | last4 = Kramer | first4 = H | last5 = Maassen | first5 = D | last6 = Matthies | first6 = HG | last7 = Musso | first7 = H | last8 = Rathjen | first8 = C | last9 = Zdhorsky | first9 = UI | year = 2003 | title = Orcein and litmus | journal = Biotechnic & Histochemistry | volume = 78 | issue = 6| pages = 289–302 | doi=10.1080/10520290410001671362| pmid = 15473576 | s2cid = 41944320 }}</ref> in a special issue of the journal Biotechnic & Histochemistry (Vol 78, No. 6) devoted to the dye.
Orcein is a reddish-brown dye, orchil is a purple-blue dye. Orcein is also used as a stain in microscopy to visualize chromosomes,<ref>{{cite journal | last1 = La Cour | first1 = L | year = 1941 | title = Acetic-orcein: a new stain-fixative for chromosomes | journal = Stain Technology | volume = 16 | issue = 4| pages = 169–174 | doi=10.3109/10520294109107302}}</ref> elastic fibers,<ref>{{cite journal | last1 = Friedberg | first1 = SH | last2 = Goldstein | first2 = DJ | year = 1969 | title = Thermodynamics of orcein staining of elastic fibres | journal = Histochemical Journal | volume = 1 | issue = 4| pages = 261–376 | doi = 10.1007/BF01003279 | pmid = 4113287 | s2cid = 11125308 }}</ref> Hepatitis B surface antigens,<ref>{{cite journal | last1 = Fredenburgh | first1 = JL | last2 = Edgerton | first2 = SM | last3 = Parker | first3 = AE | year = 1978 | title = A modification of the aldehyde fuchsin and orcein stains for hepatitis B surface antigen in tissue and a proposed chemical mechanism | journal = Journal of Histotechnology | volume = 1 | issue = 6| pages = 223–228 | doi=10.1179/his.1978.1.6.223}}</ref> and copper-associated proteins.<ref>{{cite journal | last1 = Henwood | first1 = A | year = 2003 | title = Current applications of orcein in histochemistry. A brief review with some new observations concerning influence of dye batch variation and aging of dye solutions on staining | journal = Biotechnic & Histochemistry | volume = 78 | issue = 6| pages = 303–308 | doi=10.1080/10520290410001671335| pmid = 15473577 | s2cid = 425825 }}</ref>
Orcein is not approved as a food dye (banned in Europe since January 1977), with E number E121 before 1977 and E182 after.<ref>{{Cite web|url=http://www.additifs-alimentaires.net/E121.php?src_reg|title=Additifs alimentaires – Accueil|access-date=2013-12-27|archive-date=2018-10-26|archive-url=https://web.archive.org/web/20181026182625/http://www.additifs-alimentaires.net/E121.php?src_reg|url-status=dead}}</ref><ref>{{Cite journal|url=https://www.hfpappexternal.fda.gov/scripts/fdcc/index.cfm?set=ColorAdditives|title = Color Additive Status List|journal = FDA|date = 3 February 2020}}</ref> Its CAS number is 1400-62-0.<ref>{{cite web | title = Orcein | work = CAS Common Chemistry | url = https://commonchemistry.cas.org/detail?cas_rn=1400-62-0 }}</ref> Its chemical formula is C<sub>28</sub>H<sub>24</sub>N<sub>2</sub>O<sub>7</sub>. It forms dark brown crystals. It is a mixture of phenoxazone derivates - hydroxyorceins, aminoorceins, and aminoorceinimines.
==Cudbear== '''Cudbear''' is a dye extracted from orchil lichens that produces colours in the purple range. It can be used to dye wool and silk, without the use of mordant. The lichen is first boiled in a solution of ammonium carbonate. The mixture is then cooled and ammonia is added and the mixture is kept damp for 3–4 weeks. Then the lichen is dried and ground to powder.
Cudbear was the first dye to be invented in modern times, and one of the few dyes to be credited to a named individual: Dr Cuthbert Gordon of Scotland: production began in 1758, and it was patented in 1758, British patent 727.<ref>{{Cite web|title=The Cudbear Manufactory|url=https://www.scottisharchivesforschools.org/naturalScotland/Cudbear.asp|access-date=2021-10-19|website=www.scottisharchivesforschools.org}}</ref><ref>{{cite web |url=http://www.chriscooksey.demon.co.uk/lichen/bp727.html |url-status=dead |archive-url=https://web.archive.org/web/20010221033050/http://www.chriscooksey.demon.co.uk/lichen/bp727.html |archive-date=2001-02-21 |title=Preparation of cudbear, a patent}}</ref> John Glassford invested in the new process with funds from his slave-labor tobacco business by establishing a dyeworks in Dennistoun in 1777.<ref name=":0">{{Cite web|last=Quinton|first=Rebecca|date=3 December 2019|title=Glasgow Merchants' Investment in Purple|url=https://glasgowmuseumsslavery.co.uk/2019/12/03/glasgow-merchants-investment-in-purple/|access-date=2021-10-19|website=Legacies of Slavery in Glasgow Museums and Collections|language=en}}</ref><ref>{{Cite web|last=Campsie|first=Alison|date=10 October 2021|title=9 objects that link Scotland to slavery|url=https://www.scotsman.com/heritage-and-retro/heritage/9-objects-that-link-scotland-to-slavery-3413014|access-date=2021-10-19|website=www.scotsman.com|language=en}}</ref> The manufacture details were carefully protected, with a ten-feet high wall being built around the manufacturing facility, and staff consisting of Highlanders sworn to secrecy.<ref name=":0" /> The lichen consumption soon reached 250 tons per year and import from Norway and Sweden had to be arranged.<ref>{{Cite web|url=http://gdl.cdlr.strath.ac.uk/stecit/stecit05.htm|title=Curiosities of Glasgow citizenship: George Macintosh of Dunchattan}}</ref>
A similar process was developed in France. The lichen is extracted by urine or ammonia, then the extract is acidified, the dissolved dye precipitates out and is washed. Then it is dissolved in ammonia again, the solution is heated in air until it becomes purple, then it is precipitated out with calcium chloride. The resulting insoluble purple solid is known as '''French purple''', a fast lichen dye that was much more stable than other lichen dyes.
==Gallery== <gallery> Image:alpha-aminoorcein.png|α-amino orcein Image:alpha-hydroxyorcein.png|α-hydroxy orcein Image:beta-aminoorcein.png|β-amino orcein Image:beta-hydroxyorcein.png|β-hydroxy orcein Image:beta-aminoorceinimine.png|β-amino orceinimine Image:gamma-aminoorcein.png|γ-amino orcein Image:gamma-hydroxyorcein.png|γ-hydroxy orcein Image:gamma-aminoorceinimine.png|γ-amino orceinimine </gallery>
==See also== * Litmus test * Ethnolichenology
==References== {{reflist}}
==External links== * [http://www.ravensgard.org/gerekr/Orchil.html Orchil, the poor person's purple]
{{Dyeing}}
Category:Natural dyes Category:Histotechnology Category:Food colorings Category:Staining dyes Category:PH indicators Category:Oxazines Category:Lichen products