Lichens and people
A number of dyes have been obtained from lichens and the use of lichens to produce dyes has a long history. Dyeing is also the commercially most valued application of lichens and lichen dyes had high monetary value for many centuries until the discovery of synthetic dyes in the latter half of the 19th century.
Lichens were used for the dyeing of wool and silk in ancient times and probably the most famous are the lichens known collectively in ordinary English as the orchil lichens. These were known as the sources of 'purple' dyes to the classical Greeks and Romans though the most famous (and most expensive) 'purple' dye was obtained from sea snails and gave an intense colour 'Tyrian purple'. A significant difference between the orchil and mollusc dyes was that the mollusc dye was fast whereas the orchil dye would fade in bright sunlight. The orchil dyes were at times used as a ground colour for the cloth which was then further dyed with a lesser amount of mollusc dye. In this way the use of the lichen dye allowed a given amount of mollusc dye to be used for a larger amount of cloth. Before continuing the discussion of orchil dyes two warnings are necessary. First, the words porphyra of classical Greek and purpura of Latin (which gave rise to the English word purple) encompassed a variety of colours:
'Purple' is a fluid chromatic concept in antiquity, and the ancient dye ranged in colour from bluish to deep red, depending on how it was prepared and fixed in the cloth.
This means that, though I will use the word purple in this section about dyeing, it must be taken in the broad sense just described when used to report dyes of the past. Second, over the centuries the word orchil has been used as the name of the dye or to name the lichens, though the context generally makes it clear as to whether lichen or dye is meant. I have taken much of my information about orchil from the very informative review paper listed in the following reference button.
The use of lichens as a source of purple dye was well-established in parts of the Mediterranean by Greek and Roman times. You'll often see it written that the fall of the western Roman empire saw the loss of orchil technology from western Europe until its rediscovery by a Florentine merchant, around 1300. Some dispute this, since various purple-yielding lichens are found in many parts of the western Mediterranean as well as near the coasts of northern Europe. It is possible that with the fall of the western Roman empire lichen dyes were less important as an item of trade but could still have supported cottage industries in various regions. Nevertheless it is true that the merchant Federigo (or Ferro) saw the process in the eastern Mediterranean and after returning to Florence established a very lucrative dyeing industry and amassed a fortune. The dye was known as oricello and Ferro (or Federigo) established his family name as Orcellari, with later a slight change of position of the first R to give Rucellae - and variants thereof. The origin of the name is unknown and is assumed to have been derived from some vernacular name for the dye-yielding lichens. Similar names in other languages have been orseille (French), urzella (Portuguese) orcigilia and orchilla (both Spanish) and of course the English orchil (and also archil). The Italian botanist Pier Antonio Micheli, in his 1729 work Nova Plantarum Genera, noted that Italian names for the dye-producing lichens were roccella, orcella or rasp and other Italian sources give respia and rusca as well but no trace of these forms appears to have survived to the present. Linnaeus created the species name Lichen roccella and in the current scientific classification the orchil lichens are mostly members of the genus Roccella, which is derived from that Florentine family name.
How was the dye extracted from the lichens? Here is a recipe, published in 1540 by the Venetian Giovanni Ventura Rosetti (or Rosetto) in his Plichto dell'arte de tintori:
Take one pound of Orselle of the Levant, very clean; moisten it with a little urine; add to this sal-ammoniac, sal-gemmae, and saltpetre, of each two ounces; pound them well, mix them together, and let them remain so during twelve days, stirring them twice a day; and then to keep the herb constantly moist, add a little urine, and in this situation let it remain eight days longer, continuing to stir it; you afterwards add a pound and a half of pot-ash well pounded, and a pint and a half of stale urine. Let it remain still eight days longer, stirring it as usual; after which you add the same quantity of urine and at the expiration of five or six days, two drachms of arsenic; it will then be fit for use.
The dye could then be dried and ground to a powder for easier storage or transport and rehydrated when needed for dyeing. Here is the rationale behind the above recipe (and note that stale urine is a source of ammonia):
Briefly, the preparation of purple dyes from lichens consists in the extraction of unique and particular colour-yielding depsides, such as gyrophoric, lecanoric, evernic acids and erythrin, which on decomposition give, in dyeing terminology, orcin, or its derivatives, the colour-yielding principle...This is converted by oxygen into orcein, the actual colouring matter in orchil. It appears that a single ammoniacal maceration and fermentation achieves the first two stages of the process, whilst the introduction of air by stirring completes the operation.
Suitable species of Roccella have been found beyond Europe. By the early 1400s orchil lichens were being harvested on the Canary Islands and another English vernacular name for orchil lichens is Canary Weed. Later the lichens were found in various parts of Africa, Madagascar, Asia, the Americas and Australasia. The significance of the orchil trade for the Canary Islands is shown by place names such as Roque de la Orchilla, Barranco de la Orchilla, Montaña de la Orchilla, Punta de la Orchilla and Cuevas de la Orchilla. The gathering of orchil could be very dangerous for the best grew on the cliff faces. Gatherers had to use techniques akin to those of mountaineers and contend with goats, rocks, winds and sun - all of which could generate fatigue or fatal inattention. A day's work yielded an average of 10 to 15 kilograms of orchil, though an area unexploited for a long time could yield a quintal (about 46 kilograms) of orchil in a few hours. In the 16th century collectors received 100 maravedis per quintal, which fetched 300 at the port and up to triple that on the European market. Such differences in prices favoured fraud via adulteration of the orchil with bits of vegetable matter. For a short period, ending in 1817, there was improvement in payments to gatherers and better control over fraud, but mostly the gatherers received little for their efforts. However, by 1817 the orchil trade was becoming uneconomic and after 1817 orchil export from the Canary Islands was insignificant. This was due partly to over-harvesting but cheaper supplies had become available from elsewhere and the mid-19th century saw the development of synthetic dyes that replaced many traditional dyes. Some orchil was exported from the Canary Islands until at least 1975, when it fetched the equivalent of 1000 pesetas per kilo in the Netherlands, of which the gatherers received 60.
The orchil lichens are not the only lichens to have been used in the dyeing of cloths and purples. Given the expense of orchil there was commercial incentive to find cheaper sources of the purple dyes and from the 18th century onward European manufacturers produced orchil-like dyes from various other lichens found in Europe. Litmus dye was extracted from orchil (and later non-orchil) lichens. For well over a century, until the late 1900s, it was used in the form of litmus paper to test whether a given solution was acid or alkaline. Georg Franz Hoffmann's prize-winning 1786 memoir, mentioned at the beginning of the LICHENS AND PEOPLE page, included seven plates of colour patches showing the range of colours that could be obtained from lichens. Obviously the usefulness of such plates depended on the accuracy with which they were produced. If you're curious here are Hoffmann's Plate 1 and Plate 2 (PDFs) of the copy that has been scanned for the Real Jardín Botánico de Madrid's digital library. Of course, there's also the question of how stable those printed colours have been since 1787 and how different screens show them. Nevertheless what you see on the screen should give you a good idea of some of the colours that could be produced by lichen dyes.
In modern times the best known use of lichen dyes has been in Harris Tweed which was originally dyed with vegetable and lichen dyes. Such dyes had long been used in Scotland with species of Parmelia or related genera being the commonly used lichens. The wider commercial success of Harris Tweed began in the 1840s when Catherine Murray, Countess of Dunmore, impressed by the qualities of the cloth produced by local weavers, began promoting its virtues and worked to improve production. Today the name 'Harris Tweed' is protected by UK legislation (the Harris Tweed Act, 1993, c.11) wherein Harris tweed is defined as a tweed that "has been handwoven by the islanders at their homes in the outer hebrides, finished in the outer hebrides, and made from pure virgin wool dyed and spun in the outer hebrides" - with no requirement for the use of dyes derived from plants or lichens and with Outer Hebrides uncapitalized in the legislation's text.
To finish this section I'll return to orchil with an indirect proof of its monetary value. Joaquim Pereira Marinho (1782-1854) annoyed a number of people during his first governorship of the Portuguese colony of the Cape Verde Islands, a source of orchil. His enemies accused him of various forms of misconduct, including a charge of having stolen 80 odd sacks of orchil. If you are trying to destroy a governor's career you would accuse him of a major theft, not the purloining of mere baubles.