[…] But the most important economical application of the Lichens is based on the valuable purple dyes which many species are capable of yielding. These are producible, and are usually produced in the course of manufacture, whether on the large or small scale, by the joint action of atmospheric air, water, and ammonia on certain colourless, nitrogenous, organic acids, which, from the names of the generain which they have been first or chiefly found, have been denominated by their discoverers Orcellic, Lecanoric, Gyrophoric, Evernic acids, etc. The metamorphosis of colour appears to take place, in connection with certain alkalies, by a process of oxidation; but we cannot here enter on the chemistry of the change or of its products. This subject, we are bound to confess, is in a most unsatisfactory condition: we stand much in want of a series of investigations on the composition and products of the Lichens before it can be properly understood; for hitherto scientific evidence has either been excessively vague or contradictory.
In their commercial form the purple colouring matters of Lichens constitute the pigments termed respectively Orchill, Cudbear, and Litmus, which may be practically regarded as various names for the same substance, which differs in character according to differences in the mode of its preparation,—Orchill being its English, Cudbear its Scotch, and Litmus its Dutch name,—the first being manufactured in the form of a liquid or paste of a rich purple colour, the second occurring in the form of a powder of a crimson or carmine tint, and the third being met with only in the form of small oblong cakes of an indigo-blue colour. Their colour is naturally reddish: the blue tint is communicated by the addition of alkalies, while consistence is produced by chalk, gypsum, and similar substances in a state of powder.
These colouring matters, in some of their forms, have probably been known from remote antiquity. There is reason to believe that the dye mentioned in Ezekiel (c. xxvii. V. 7)—"Blue and purple from the isles of Elishah was that which covered thee," and the celebrated "purple of Amorgos," were orchill.
These dyes, which we may hence forth, for convenience' sake, denominate Orchill,—the name by which their chief form has been longest familiar in commerce,—are now largely employed, chiefly in combination with other colouring matters, in dyeing or staining with various shades of red, purple, or blue, woollen, silk, and cotton fabrics, leather, wood, marble, feathers, and paper; in the making of size-paint for walls, and of the pigments termed lakes.
The rationale of their manufacture is the making of the cleansed and powdered Lichen into a pulp with water; the addition of an ammoniacal liquid, chiefly in the form of gas-liquor; and the maceration of the mass in a moderately warm locality, for periods varying from several days to several weeks. A process of fermentation takes place, and by the end of this period the mass has assumed a beautiful purple colour, and retains a peculiar ammoniacal aroma.
This process the student may imitate for himself on the small scale, and may thus be enabled to test the colorific value of common native species. He has merely to macerate, in a small vial or other convenient vessel containing a mixture of hartshorn (liquid ammonia) and water, sufficiently strong to be disagreeably pungent; a small quantity of the powdered Lichen; if it contain any of the colourless colorific principles capable of generating purple dyes, the liquid will speedily assume a reddish tint, which, should they be abundant, will become developed into a rich purple. He may use more elegant colorific tests, but we are convinced, from our own experience, that none will be found so easy and so successful as the above. He may make in a test-tube an alkaline or alcoholic solution of the Lichen, by boiling or maceration; the addition of a few drops of a solution of common bleaching powder (chloride of lime) will then cause the development of a fugitive red tint, if it contain any of the colorific principles in question.
* The results were laid before the meeting of the British Association, at Glasgow, in September, 1855, and before the Botanical Society of Edinburgh on various occasions daring the years 1852, 1853, and 1854; vide Edin. New Philos. Journal, Oct. 1854, Jan. and July, 1855; 'Phytologist,' vol. iv. pp. 867, 901, 998, 1068, and vol. v. p. 179. Series of specimens, preparations, and drawings, illustrative of the economical applications or uses of British and Foreign Lichens (collected or made by the Author) will be found in the National Industrial Museum for Scotland, and in the Museum of Economic Botany, Royal Botanic Garden, Edinburgh.This reaction depends on the circumstance of this solution (which may be considered chemically a solution of hypochlorite of lime) striking a fugitive blood-red colour with any of the organic acids before mentioned. Or he may macerate the Lichen in milk of lime, and precipitate by hydrochloric or acetic acid its colorific principles, which he can subsequently collect and weigh. By the aid of such simple chemical experiments we some years ago made a series of investigations, with a view to ascertain whether many native and colonial Lichens could not be made available in dyeing, and especially as substitutes for the comparatively few and expensive species now employed in the manufacture of orchill, cudbear, and litmus.* We cannot specialize the results, but they were sufficiently encouraging to warrant us in recommending the subject to the attention of all who are likely to travel, at home or abroad, in localities which are rich in crustaceous and fruticulose Lichens,— that is, in mountainous or maritime districts.
We found that the species most likely to yield valuable colorific results are those growing on rocks, having a crustaceous, whitish, warted, friable thallus; that, to a certain extent, colorific quality is proportionate to the kind or degree of sorediiferous degeneration of the thallus; that showy foliaceous species are least likely to yield purple dyes, though they frequently furnish yellowish', greenish, reddish, or brownish colouring matters; and that, short of actual experiment, it is impossible to predicate colorific value, the colour of the thallus being a most deceptive guide.
The genera containing the most valuable dye species are Roccella, Lecanora, Umbilicaria, Parmelia, Urceolaria, Physcia, and Ramalina. A few species belonging to one or more of these genera have long been employed by manufacturers in the preparation of orchill, cudbear, or litmus, such as Roccella tinctoria and fuciformis by the English orchill maker, or Lecanora tartarea by the Scotch cudbear-maker and Dutch litmus-maker.
Other species have recently been introduced, either as supplementary or substitutional species, such as Umbilicaria pustulata, Parmelia perlata, and Lecanora pallescens var. parella. For the purposes of British manufacture none of these are collected from the rocks of our own highlands and islands, but are procured from the African coasts and islands or the mountains of Norway, at a considerable expense; while there is reason to believe that many species possessing similar, if not equally valuable, colour-yielding properties, might be gathered at home at an infinitely cheaper rate.
When the cudbear manufacture, which is now extinct in Scotland, flourished in Leith and Glasgow, large quantities of Lecanora tartarea were collected by the peasantry of the western highlands and islands; and the revival and extension of this traffic would probably prove a great boon to that remnant of the Celtic race, which is fast disappearing from our shores to spend its energies in foreign climes. Under various vernacular names species of the same genera have for ages been employed by the peasantry of this and other countries, to yield pigments wherewith they dyed their yarn and home-spun fabrics.
In Scotland, not many years ago, particularly in certain districts, almost every farm and cotterhouse had its tank or barrel of "graith," or putrid urine (the form of ammoniacal liquid employed), and its "lit-pig," wherein the mistress of the household macerated some familiar "crottle" (the Scotch vernacular term for the dye-lichens in general), such as Lecanora tartarea or Parmelia saxatilis, and prepared therefrom a reddish or purplish dye. The commercial designation of the dye-lichens depends upon the thallus being erect or pendulous and cylindrical or shrubby on the one hand, and flat, crustaceous, or foliaceous on the other; species having a thallus of the former character being termed "weeds," as the Roccella; and of the latter "mosses," as the Lecanoras and Parmelias.
The "weeds" chiefly used in the preparation of orchill, the Roccella, are popularly called "Orchella weeds," and are somewhat specifically arranged in commerce according to their geographical sources, as "Angola, Lima, Cape, or Canary Orchella weeds."
The "mosses" are more irregularly designated, the specific name in some being due to their geographical source, as "Canary rock- moss;" in others, to their physical characters, as "Tartareous, or Pustulatous, moss."
We have spoken of colouring matters which are produced by the metamorphosis of colourless organic acids; but some Lichens possess brilliant yellow or greenish colouring matters, also of an acid nature, which exist ready formed in, and give the predominant tint to, the thallus of the plant. Such colouring matters are the Vulpinic acid of Cornicularia vulpina, and the Parietinic acid of the common yellow Wall Lichen (Parmelia parietina). From the purple colour which it strikes with alkalies, the latter acid has been proposed as a test for that class of bodies: it is also one of the colouring matters of medicinal rhubarb,—an interesting instance of the analogies, in composition and products, between the Lichens and phanerogamic plants.
We may here further cite, as illustrations of these analogies, the occurrence of fumaric or paramaleic acid,—which is moreover producible artificially from malic or maleic acid, the sour principles of the apple and other acid fruits,—equally in Cetraria Islandica and Fumaria officinalis, the common Fumitory of our fields; of oxalic acid, in the form of various salts, equally in many Lichens to a large extent, and in garden rhubarb, sorrel, and other phanerogams; and of an oil similar to the furfurol of bran and the fucusol of seaweeds, which is producible by distilling Cetraria Islandica, Usnea barhata, and other Lichens with certain proportions of sulphuric acid and water.
Brownish colouring matters, ready formed in the thallus, also exist abundantly in many Lichens, and are easily extracted; they are the basis of various dyes prepared by the peasantry of this and other countries, but they are not of sufficient value ever to have been manufactured or applied on the large scale. It will thus be remarked that the only matters really valuable in dyeing are the product of the chemical metamorphosis of colourless compounds, which usually exist in species devoid of vivid or deep tints.
Lichens, in consequence chiefly of imaginary virtues, were at one time employed in various arts, in which their use is now totally abandoned. From their alleged aptitude for imbibing and retaining odours or scents, the powder of several filamentous and fruticulose species formed the basis of certain perfumes which were celebrated in the seventeenth century, and of which the chief was designated the "Poudre de Chypre" (Pulvis Cyprius), or Cyprian hair-powder: these were popularly believed to remove scurf, and to clean and promote the growth of hair.
The astringency of some species rendered them serviceable in tanning and brewing; the beer of a certain Siberian monastery, which at one time acquired a celebrity from its peculiar bitterness, owed this to Sticta pulmonaria. The gum of some species has been used in paper, pasteboard, and parchment-making, in weaving, and in calico-printing; and various dried species have been used instead of straw, or a similar material, in the packing, for transport, of furniture, fruit, etc.
Bibliography:
[…]
Tinctorial Properties, Dyeing Matters, and General Chemistry:
— Stenhouse in Philosophical Transactions, 1848:
Proceedings of Philosophical Society of Glasgow, 1848-49:
London, Edinburgh, and Dublin Philosophical Magazine, 1848, etc.:
Kane in Philosophical Trans., 1840:
Westring in the Stockholm Transactions, 1792 to 1799:
Papers by Schunck, Laurent and Gerhardt, Eochleder and Heldt, Schnedermann and Kopp, Herberger, Heeren, Schlossberger, etc., in the Annates de Chimie, Liebig and Kopp's Aunalen, Journal de Pharmacie et de Chimie, the Philosophical and Linnean Trans., Chemical Gazette, and other chemical and scientific journals of Britain and the Continent:
Edmonston On the Native Dyes of the Shetland Islands, in Trans. Bot an. Society of Edinb.,' vol. i.:
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Runge, Farben-Chimie:
Pereira in Pharmaceutical Society's Trans., vol. ix. (Litmus):
Bory de St. Vincent, Essais sur les Des Fortunées, 1803:
Berzelius, Traité de Chimie:
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Berthollet, Elémens de l'art de la Teinture:
Bancroft, Philosophy of Permanent Colours. General Economical Applications:
—Amoreux, Recherches et Expériences sur les divers Lichens dont on peut faire usage en Médecine et dans les Arts:
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Lord Dundonald in 'Philosophical Magazine,' vol. x
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