text: This test uses a saturated solution of calcium hypochlorite (bleaching powder), or alternatively a dilute solution (5.25% is typically used) of sodium hypochlorite, or undiluted household bleach. These solutions are typically replaced daily since they break down within 24–48 hours; they break down even more rapidly when exposed to sunlight (less than an hour) and so are recommended to keep in a dark-coloured bottle. Other factors that accelerate the decomposition of these solutions are heat, humidity, and carbon dioxide.
  Colours typically observed with the C test are red and orange-rose. Chemicals causing a red reaction include anziaic acid, erythrin, and lecanoric acid, while those resulting in orange-red include gyrophoric acid. Rarely, an emerald-green colour is produced, caused by reaction with dihydroxy dibenzofurans, such as the chemical strepsilin. Another rare colour produced by this test is yellow, which is observed with Cladonia portentosa as a result of the dibenzofuran usnic acid.
  Some common and widely distributed lichens that have lichen products with a positive reaction to C include Lecanora expallens, which is C+ (orange) because of the xanthone thiophanic acid, and Diploschistes muscorum, which is C+ (red) because of the didepside diploschistesic acid.