Dyeing is the art of giving colour to textile and other articles in such a way that the colours are more or less permanent, and not readily affected by the action of light, washing, etc. Like spinning and weaving it was originally a home industry, as it still is in many places. Until about 1850 natural dye-stuffs alone were employed, but the discovery of dyes of all colours that can be obtained from coal-tar products revolutionized dyeing as an industry, and the vegetable dye-stuffs were gradually superseded by the newer colours.
Before dyeing, the materials have generally to be cleansed or bleached to get rid of undesirable colouring matters or impurities; and frequently a textile material is subjected to some subsidiary treatment in order to obtain special effects. For example, cottonyarn may be subjected to the action of strong causticsoda ('mercerizing' process) while in a state of great tension, in order to give it a permanent silky lustre.
Dyeing is not only an art, it is also a branch of applied chemistry. One fundamental principle is, that the colouring matter and other necessary substances must be applied in a state of solution, and while in direct contact with the fibre they must be rendered insoluble, so that they are precipitated within or upon the fibre and thus permanently fixed. The method of effecting this varies greatly according to the fibre and the colouring matter employed. As a rule the vegetable and the animal fibres are dyed by very different methods. The affinity of the animal fibres for certain colouring matters is often so great that they are readily dyed by simple immersion in hot colour solutions;
but this simple process is not generally sufficient. According to the method of their application in dyeing the following groups: of dye-stuffs may be distinguished: Avid Colours, Basic Colours, Direct Colours, Developed Colours, Mordant Colours, Miscellaneous Colours, Reactive Colours.
The acid colours are so called because they are of an acid character and are applied in an acid dye-bath. As a rule, they are only suitable for dyeing the animal fibres, e.g. wool and silk, also leather, horn, feathers, etc. Only a few vegetable dye-stuffs belong to this class, for example, the purple colour orchil and the blue colour indigo extract. On the other hand, the acid colours derived from coal-tar - and increasingly petroleum - are very numerous and yield a great variety of hues - red, orange, yellow, green, blue, violet, brown, and black, each with its particular name.
The basic colours are so called because their essential constituents, to which they owe their dyeing power, are organicbases. The bases themselves are colourless and too insoluble in water to be of use, hence they are employed in the form of their soluble coloured salts, usually the hydrochlorides of the colour-bases. Their solutions are precipitated by tannic acid, because it combines with the colour-bases to form insoluble tannates. Wool, silk, and animal substances generally have a direct attraction for colour-bases, and hence these fibres are readily dyed by simple immersion in hot aqueous solutions of the basic colours. Cotton and linen, on the other hand, are not dyed so readily; they need first to be prepared or impregnated with tannic acid, and thus prepared are said to be mordanted, the tannic acid in this connection being styled the mordant. Most of the colours of this class are fugitive to light, and all but one, barberryroot, are derived from coal-tar products.
The direct colours are so called because they dyecotton direct, that is, without the aid of any mordanting process. The first of this class derived from coal-tar was congo red, discovered in 1884; this group includes a very great variety of fast colours, and forms, indeed, one of the most important and valuable series of dye-stuffs employed. Cotton, linen, and the vegetable fibres generally are dyed in the simplest possible manner by merely boiling them in a solution of the dye-stuff, with or without the addition of a little soap, carbonate or sulphate of soda, etc. Wool and silk are frequently dyed in the same manner as cotton. Very few vegetable dye-stuffs belong to the direct colours, e.g. Safflower, Turmeric, Saffron, Annatto. They are all fugitive, and have been of little or no importance to the dyer since the end of the 19th century. The coal-tar colours of this class, on the other hand, are extremely numerous.
The developed colours include a variety of colours which are formed in situ upon the fibre by the successive application of two or more substances. These colours are all of coal-tar origin. A number of them belong to the so-called azo colours, derived from compounds containing nitrogen.
The mordant colours form one of the most important classes of colouring matters, for they include not only most of the vegetable dye-stuffs, e.g. madder, logwood, fustic, etc, but also many valuable fast coal-tar colours, commonly known as the alizarin colours, after their typical representative, alizarin. These mordant colours have by themselves very little colouring power, as a rule, and if employed alone in dyeing give little or no result. If applied, however, in conjunction with metallic salts, notably those of chromium, aluminium, iron, tin, and copper, they each yield a variety of colours, according to the metallic salt employed. In employing them usually two distinct operations are involved: first, that of applying the metallic salt or mordant, called the mordanting process ; and second, that of dyeing proper, in which the mordanted material is boiled in a solution or decoction of the dye-stuff. During the dyeing operation the colouring principle of the dye-stuff combines with the metallic salt already upon the material, and the colour is thus produced and fixed upon the fibre. The method of mordanting varies with the fibre and the metallic salt employed. The vegetable dye-stuffs of this class include Madder, Sapanwood, Camwood, Barwood, Old Fustic, Young Fustic, Quercitron Bark, Persian Berries, Weld, Logwood. Madder was formerly the most important and highly valued of the dye-stuffs of this class, being especially employed to produce the fine 'Turkey-red' dye; but was entirely superseded by the coal-tar colour alizarin towards the end of the 19th century.
Reactive colours combine directly with the fibre being dyed through a chemical reaction and result in a fast colour. The first ranges of reactive dyes for cellulose fibres were introduced in the mid-1950s.
Similarly, the employment of cochineal (an insect dye) has also greatly diminished through the introduction of the cheaper colours. Camwood and barwood are almost entirely used in wool-dyeing, either in conjunction with the indigo-vat or for the purpose of dyeing various shades of brown. Old fustic is the most important of the yellow mordant dye-stuffs, and the colours are fast although not very brilliant. Young fustic yields fugitive colours, and has been little used since 1900. Quercitron bark is an excellent dye-stuff employed by wool-dyers for the production of bright orange and yellow colours. Persian berries and weld, a species of wild mignonette, are both excellent dye-stuffs, but their employment is now limited. Logwood is largely employed by wool, silk, and cotton dyers for dyeing black and dark-blues, which, although fast to washing, are only moderately so towards light. During the 20th century dyewoods were gradually replaced by coal-tar colours.
Among miscellaneous colours are several dye-stuffs applied in a distinct manner. Indigo is a dark-blue powder quite insoluble in water, but can be rendered soluble for dyeing purposes by two methods. The first method converts the indigo into so-called indigo extract, which is sold as a blue paste and applied as an acid colour in dyeing wool and silk. In the second method the indigo-blue is converted into indigo-white, which readily dissolves in the alkalipresent, the solution thus obtained being called an indigo-vat. If cotton, wool, or silk is steeped for some time in the clear yellow solution of such a vat, and then exposed to the oxidizing influence of the air, they are dyed a permanent blue. The indigo-white absorbed by the fibre loses its acquired hydrogen, and thus insoluble indigo-blue is regenerated within and upon the fibre. Aniline black is a valuable colour, produced direct upon the fibre by the oxidation of aniline, and remarkable for its extreme permanency.
Catechu is a vegetable dye-stuff used in dyeing cotton and woollen brown. On wool, catechu yields khaki browns in single bath by using copper sulphate as the mordant. On silk it is largely employed for weighting purposes in the process of dyeing black. Chrome Yellow, Iron Buff, Prussian Blue, and Manganese Brown, employed in cotton dyeing, are frequently classed as mineral colours. Chrome yellow is obtained by immersing cotton successively in solutions of acetate of lead and bichromate of potash, whereby the yellow precipitate of chromate of lead is fixed upon the fibre. Iron buff is obtained in a similar manner by the successive application of iron sulphate and carbonate of soda, and finally developing the full colour by washing with water and exposure to air. The buff colour is really due to the precipitation of oxide of iron on the cotton. Prussian blue is at once developed by passing the buff-dyed cotton through an acidified solution of potassium ferrocyanide. The production of manganese brown on cotton is similar to that of iron buff. The brown colour ultimately produced upon the fibre is an oxide of manganese. The mineral colours are very useful for certain purposes, and are to be regarded as very fast to light. Research Dyeing
German Paste was the name given to a kind of paste formerly made for feeding cage-birds, such as canaries, larks, nightingales, etc, during the Victorian era. The following is one of various recipes: one pound of pea-meal, half a pound of blanched sweet almonds, two ounces of fresh butter, two ounces of moist sugar, fifteen grains of hay saffron. Mix and beat well with a little water, pass through a cullender, then expose to the air until dry. Research German Paste
Cocoa (Cacao) is a small tree (Theobroma cacao) of the family Sterculiaceae, natural order Byttneriaceae native to tropical America. The tree is five to six metres high and much cultivated in the tropics of both hemispheres, especially in the West Indian Islands, Central and South America and Africa. The leaves are about 10 cm in length, smooth but not glossy, and of a dull-green colour; the flowers are saffron-coloured, and very beautiful.
The fruit consists of pointed, oval, ribbed pods 15 to 25 cm long. The cultivated trees bear fruit all the year round, but the gathering is chiefly in June and December. The pods are removed by knives attached to the ends of poles. The pods are at first green, but as they ripen they change to a fine bluish-red, or almost purple colour, and in some varieties to a yellow or lemon colour. Each pod encloses 50 or more seeds in a white, sweetish pulp; and the seeds or 'beans' have each a parchment-like covering enclosing a whitish pulp. These are very nutritive, containing 50 per cent of fat, are of an agreeable flavour, and used, both in their fresh state and when dried, as an article of diet. Cocoa and chocolate are made from them, the former being a. powder obtained by grinding
the seeds, and often mixed with other substances when prepared for sale, the latter being this powder mixed with sugar and various flavouring matters and formed into solid cakes. The seeds when roasted and divested of their husks and crushed are known as cocoa nibs. The seeds yield also an oil called butter of cacao, used in pomatum and for making candles, soap, etc.
The best quality cocoa comes from Venezuela, Ecuador, the Caribbean (Jamaica, Trinidad and Greanada) and Madagascar. This accounts for about two percent of the cocoa produced, the remaining 98 per cent is low grade cocoa lacking aroma and quality, and which is used in 99.99 per cent of commercial chocolate. Research Cocoa
Colchicum is a genus of autumnal-blooming plants of the family Liliaceae which includes the meadow saffron. Many of them are very handsome, the colours being mostly purple or white, and the flowers similar to crocuses. The colchicums are natives of southern Europe and western Asia.
From a small corm or bulb buried about 15 cm deep, and covered with a brittle brown skin of the meadow saffron there rises in the early autumn a tuft of flowers having much the appearance of crocuses, flesh-coloured, white, or even variegated. They soon wither, and the plant disappears until the succeeding spring, when some broad leaves are thrown up by each corm along with a triangularoblong seed-vessel. The plant is acrid and poisonous, and cattle are injured by eating it, but it yields a medicine - colchicin - valuable in gout and rheumatism. Research Colchicum
The Crocus is a genus of plants of the family Iridaceae or Iris, forming one of the most common ornaments of the garden. They are natives to the northern parts of the Old World, especially southern Europe and the Middle East, and three grow wild in Britain. They may be divided, according to their period of flowering, into vernal and autumnal. Among the vernal crocuses may be mentioned the white and purple Crocus vernus; Crocus versicolor, distinguished by the yellow tube of its flower bearded with hairs, and its sweet scent; Crocus biflorus, the Scotch crocus, with beautiful pencilled sepals, and clear or bluish-white petals. Among the autumnal species are Crocus nudiflorus and Crocus sativus, whose long, reddish-orange, drooping stigmas, when dried, form saffron. Research Crocus More pictures of Crocus
Meadow saffron (Colchicum autumnale) or autumn crocus, is a highly poisonous perennialherb of the family Liliaceae with an underground, brown, scaly corn which bears solitary, long violet and tubular crocus-like flowers in the autumn. The flowers differ from the crocuses in having six rather than three stamens. Research Meadow Saffron
Saffron (Crocus sativus) is a perennialherb of the family Iridaceae with a scaly underground corm and linear leaves with a pale midrib. The short scrape is terminated by a large pale-violet, six-lobed, funnel-shaped flower. The yellow style is tipped with three orange stigmas that extend beyond the perianth. The saffron used in cooking is the dried stigmas.
Saffron was first cultivated on a large scale in England at Saffron Walden by Thomas Smith, secretary of state to Edward VI. Research Saffron
Shoeblack was a Victorian name for someone who shined strangers shoes for a living. In Victorian London shoeblacks were licensed and brigades were established, distinguished by their red uniform, to provide employment to 'poor and honest boys'. The first London shoeblack brigade was the Ragged Schools brigade of Saffron-Hill. In 1888 itt was reported that the average earning for a shoeblack brigade boy was in the region of ten shillings a week. Research Shoeblack
Saffron Burrows is an English actress and model. She was born in 1973 at London. After studying drama she was discovered for modeling when she was 15 but made her first film two years later and left modelling for acting. Research Saffron Burrows
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Dyeing
