E. Dyeing Properties of Lichens

a. Lichens as Dye-plants. Knowledge as to the dyeing properties of lichens dates back to a remote antiquity. It has been generally accepted that lichen-colours are indicated by the prophet Ezekiel in his denunciation of Tyre: “blue and purple from the Isles of Elishah was that which covered thee.” Theophrastus describes certain plants as growing in Crete, and being used to dye wool, etc., and Pliny in his Phycos Thalassion is also understood as referring to the lichen Roccella, “with crisp leaves, used in Crete for dyeing garments.”

Information as to the dyeing properties of certain lichens is given in most of the books or papers dealing with these plants from the herbals onwards. Hoffmann[1296] devoted a large part of his Commentatio de vario Lichenum usu to the dye-lichens, and, illustrating his work, are a series of small rectangular coloured blocks representing samples of woollen cloth dyed with different lichens. There are seventy-seven of these samples with the colour names used by French dyers.

An important treatise on the subject translated into French was also contributed by Westring[1297]. He desired to draw attention to the tinctorial properties of lichens other than the Roccellae which do not grow in Sweden. The Swedes, he states, already used four to six lichens as dye-plants, but only for one colour. He demonstrated by his improved methods that other colours and of finer tint could be obtained. He describes the best methods both of extraction and of dyeing, and then follows with an account of the different lichens likely to be of service. The treatise was subsequently published at greater length in Swedish[1298] with twenty-four very fine coloured illustrations of the lichens used, and with sample blocks of the colours to be obtained.

b. The Orchil Lichen, Roccella. The value of Roccella as a dye-plant had been lost sight of until it was accidentally rediscovered, early in the fourteenth century, by a Florentine merchant called Federigo. He introduced its use into Florence, and as he retained the industry in his own hands he made a large fortune, and founded the family of the Orcellarii, called later the Rucellarii or Rucellai, hence the botanical name, Roccella. The product was called orseille for which the English name is orchil or archil. Another origin suggested for orchil is the Spanish name of the plant, Orcigilia. There are a number of different species that vary in the amount of dye-product. Most of them grow on rocks by the sea-side in crowded bluish-grey or whitish tufts of strap-shaped or rounded stiff narrow fronds varying in length up to about six inches or more. The main supply of “weeds” came from the Levant until the fifteenth century when supplies were obtained from the Canaries (long considered to produce the best varieties), Cape Verd and the African coasts. The geographical distribution of the Roccellae is very wide: they grow on warm sea-coasts all over the globe, more particularly in Angola, the Cape, Mozambique, Madagascar, in Asia, in Australia, and in Chili and Peru.

Zopf[1299] has proved the existence of two different colouring substances among the Roccellas: in R. fuciformis ([Fig. 57]) and R. fucoides (both British species), in R. Montagnei and R. peruensis the acid present is erythrin; in R. tinctoria, R. portentosa and R. sinuensis it is lecanoric acid. In R. tinctoria ([Fig. 133]), according to Ronceray[1300], the acid is located chiefly in the gonidial layer and the soredia but is absent from the cortex and centre. In R. portentosa it is abundant in the cortex and central layer, while scarcely to be detected in the gonidial layer, and it is wanting altogether in the soredia. In R. Montagnei it is chiefly found in the cortex and the gonidial layer, and is absent from the soredia and from the medulla.

c. Purple Dyes: Orchil, Cudbear and Litmus. Orseille or orchil is formed not only from erythrin and lecanoric acid (orseillic acid), but also from erythrinic, gyrophoric, evernic and ramalic acids[1301] and may be obtained from any lichen containing these substances. By the action of ammonia the acids are split up into orcin and carbonic acid. In time, under the influence of ammonia and the oxygen of the air[1302], orcin becomes orcein which is the colouring principle of orchil; the perfecting of the process may take a month. The dye is used for animal fibres such as wool and silk; it has no effect on cotton.

There are several different preparations on the market, chiefly obtained from France and Holland; orchil or orseille in the form of a solution, cudbear (persio of Germany) almost the same, but manufactured into a violet-reddish powder, and litmus (tournesol of France) which is prepared in a slightly different manner. At one time the lichen, broken into small pieces, was soaked in urine; a fermentation process was set up, then lime and potash with an admixture of alum were added. The mass of material when ready was pressed into cubes and dried in the air. Commercial litmus contains three substances, erythrolein, erythrolitmin and azolitmin; the last named, which is the true litmus, is a dark brown amorphous powder soluble in water, and forming a blue solution with alkalies.

Fig. 133. Roccella tintoria Ach. From the Cape of Good Hope.

An aqueous solution of litmus when exactly neutralized by an acid is violet coloured; it becomes red with the smallest trace of free acid, or blue with free alkali. Litmus paper is prepared by steeping specially prepared unsized paper in the dye solution. It is as a ready and sensitive indicator of acidity or alkalinity that litmus is of so much value. According to Zopf[1303] it is also used as a blueing agent in washing and as a colouring of wine. Litmus is chiefly manufactured in Holland. Still another substance somewhat differently prepared from the same lichens is sold as French purple, a more brilliant and durable colour than orchil.

Fig. 134. Lecanora tartarea Ach. (S. H., Photo.).

d. Other Orchil Lichens. Though species of Roccella rank first in importance as dye-plants, purple and blue colours are obtained, as indicated above, from other very different lichens. Lindsay[1304] extracted orchil from about twenty species. Those most in use in northern countries are on the whole less rich in colouring substances; they are: Umbilicaria pustulata, species of Gyrophora, Parmelia and Pertusaria, and above all Lecanora tartarea ([Fig. 134]). The last named, one of the hardiest and most abundant of rock- or soil-lichens, is chiefly used in Scotland and Sweden (hence the name “Swedish moss”) to furnish a red or crimson dye. In Scotland all dye-lichens are called “crottles,” but the term “cudbear” was given to Lecanora tartarea (either the lichen or the dye-product); it was acquired from a corrupt pronunciation of the Christian name of Dr Cuthbert Gordon, a chemist, who, according to Bohler[1305], obtained a patent for his process of producing the dye, or who first employed it on a great scale in Glasgow. Johnson[1306] remarks that the colour yielded by cudbear, if well prepared, is a fine, clear, but not very bright purple. It is, he alleges, not permanent. Like other orchil substances it is without effect on cotton or linen.

e. Preparation of Orchil. A general mode of treatment of dye-lichens recommended by Lauder Lindsay[1307] for home production of orchil, cudbear and litmus is as follows:

1. Careful washing, drying and cleansing to separate earthy and other impurities.

2. Pulverization into a coarse or fine pulp with water.

3. Repeated addition of ammoniacal liquor of a certain strength, obtainable from several sources (e.g. putrid urine, gas liquor, etc.).

4. Frequent stirring of the fermenting mass so as to ensure full exposure of every part thereof to the action of atmospheric oxygen.

5. Addition of alkalies in some cases (e.g. potash or soda), to heighten or modify colour; and of chalk, gypsum and other substances to impart consistence.

f. Brown and Yellow Dyes. The extracting of these colours from lichens is also a very old industry. Linnaeus found during his journey to Lappland[1308], undertaken when he was quite a young man, that the women in the northern countries made use of a brown lichen for dyeing which is evidently Parmelia omphalodes ([Fig. 135]). He describes it as a “rich Lichenoides of a brown stercoraceous colour,” and he has stated that it grew in such abundance in the Island of Aland, that every stone was covered, especially near the sea. In the Plantae tinctoriae[1309] there is a record of six other lichens used for dyeing: Lichen Roccella, L. tartareus, L. saxatilis, L. juniperinus, L. parietinus and L. candelarius. The value of Lichen omphalodes was also emphasized by Lightfoot; the women of Scotland evidently appreciated its dyeing properties as much as other northern peoples.

A series of memoirs on the utility of lichens written by Willemet[1310], Amoreux and Hoffmann, and jointly published at Lyons towards the end of the eighteenth century, represents the views as to the economic value of lichens held by scientific botanists of that time. All of them cite the various dye-species, and Hoffmann, as already stated, gives illustrations of colours that can be obtained. It has been once and again affirmed that Parmelia saxatilis yields a red colour, but Zopf[1311] denies this. It contains saxatillic acid which is colourless when extracted but on boiling gives a clear reddish-yellow to reddish-brown solution which dyes wool and silk directly without the aid of a mordant. Zopf[1311] observed the process of dyeing followed in South Tyrol: a layer of the lichen was placed in a cooking pot, above this a layer of the material to be dyed, then lichen and again the material until the pot was filled. It was covered with water and boiled three to four hours, resulting in a beautiful rust-brown and peculiarly fast dye.

Fig. 135. Parmelia omphalodes Ach. (S. H., Photo.).

Reddish- or rust-brown dye is also obtained from Haematomma ventosum and H. coccineum, a yellow-brown from Parmelia conspersa (salazinic acid), and other shades of brown from Parmelia perlata, P. physodes, Lobaria pulmonaria and Cetraria islandica.

Yellow lichens in general furnish yellow dyes, as for instance Xanthoria parietina which gives either brown or yellow according to treatment and Cetraria juniperina which forms a beautiful yellow colouring substance on boiling. Teloschistes flavicans and Letharia vulpina yield very similar yellow dyes, and from Lecanora parella ([Fig. 39]), Pertusaria melaleuca and Usnea barbata yellow colours have been obtained. Candelariella vitellina and Xanthoria lychnea both contain yellow colouring agents and have been employed by the Swedes for dyeing the candles used in religious ceremonies.

g. Collecting of Dye-lichens. Lauder Lindsay[1312] made exhaustive studies of dye-lichens both in the field and in the laboratory, and recorded results he obtained from the micro-chemical examination of 540 different specimens. He sought to revive and encourage the use of their beautiful colour products among country people; he has given the following practical hints to collectors:

1. That crustaceous dwarf pale-coloured species growing on rocks, and especially on sea-coasts, are most likely to yield red and purple dyes similar to orchil, cudbear or litmus; while on the other hand the largest, most handsome foliaceous or fruticose species are least likely.

2. That the colour of the thallus is no indication of colorific power (in orchil lichens), inasmuch as the red or purple colouring substances are the result of chemical action on crystalline colorific “principles” previously devoid of colour.

3. That alterations in physical characters, chemical composition and consequently in dyeing properties are very liable to be produced by modification in the following external circumstances:

August has been recommended as the best month for collecting dye-lichens: i.e. just after the season of greatest light and heat when the accumulation of acids will be at its maximum.

Some of the acids found useful in dyeing occur in the thalli of a large number of lichens, many of which are too scantily developed to be of any economic value. Thus salazinic acid which gives the effective yellow-brown dye in Parmelia conspersa was found by Zopf in 13 species and varieties. It has since been located by Lettau[1313] in 72 different lichens, many of them, however, with poorly developed or scanty thalli, so that no technical use can be made of them.

h. Lichen Colours and Spectrum Characters. In a comparative study of vegetable colouring substances, Sorby[1314] extracted yellow colouring matters from various plants distinguished by certain spectrum characters. He called them the “lichenoxanthine group” because, as he explains, “these xanthines occur in a more marked manner in lichens than in plants having true leaves and fronds.” Orange lichenoxanthine he found in Peltigera canina, Platysma glaucum, etc., when growing well exposed to the sun. Lichenoxanthine he obtained from the fungus Clavaria fusiformis; it was difficult to separate from orange lichenoxanthine. Yet another, which he terms yellow lichenoxanthine, he obtained most readily from Physcia (Xanthoria) parietina. The solutions of these substances vary according to Sorby in giving a slightly different kind of spectrum. He did not experiment on their dyeing properties.