DUTCH GOLD. See Alloy.
DUTCH LIQ′UID. See Olefiant Gas.
DYE′ING. The act of tinging or colouring absorbent materials by impregnating them with solutions of colouring matters or dye-stuffs. The colouring matters which impart their tints without the intervention of other substances are called ‘substantive colours’; while those which require such aid are called ‘adjective colours.’ The bodies employed to fix and develop the latter class are called ‘mordants.’ The exact way in which dye-stuffs act upon fibrous materials has not yet been investigated as fully as it deserves; the generally received opinion is that the fibre has a chemical affinity for the colouring matter in the case of substantive dyes, and likewise for the mordant, which, in its turn, has an affinity for the colouring matter of adjective dyes. Another opinion is that the fibres have pores, which, when expanded by heat or chemical agents, admit particles of colouring matter. However this may be, it is certain that different materials ‘take’ dyes in different proportions; thus, silk and wool take the coal-tar dyes in the most perfect manner, but cotton requires the intervention of a most powerful mineral or animal mordant. Wool takes the colouring matters of most dye-stuff so well that the deepest tints can readily be produced. Silk and COTTON are dyed with greater difficulty, whilst LINEN shows still less disposition to take dyes. The operations which take place in dyeing are ‘mordanting,’ ‘ageing,’ ‘dunging,’ ‘dyeing,’ and ‘clearing.’ The first of these operations is noticed under Mordant. After the fabric has been mordanted, it is generally hung up in a room through which a current of steam and air is passing, by means of which the union between the fibre and the mordant is quickened very considerably. This exposure to moist air is the step in the process to which the term ‘ageing’ is applied. The operations of ‘dunging’ and ‘clearing’ are noticed above (see Dunging). The ‘dyeing’ proper, which follows the ‘dunging,’ is effected by running the fabric through the solution of the dye-stuff, the colour being modified more or less by the nature of the mordant used. Under the names of the different colours the means used to dye such colours are minutely described. See Black Dye, Blue Dye, &c.
The following particulars respecting the production of the more common colours may prove interesting to the reader, who merely requires some general information on the subject:—
Black is usually produced by logwood or galls with an iron mordant. Common black silks are dyed with logwood and fustic, iron being used as a mordant. The best silks are dyed black on a blue ground. Woollen goods are first dyed blue with indigo, and afterwards with sumac, logwood, and green or blue copperas. Cotton and linen goods are dyed black in a very similar manner.
Blue is commonly produced from indigo, either in the form of sulphate or in aqueous solution. Prussian blue, with a persalt of iron or tin as a mordant, gives a very splendid dark blue. Of late several blues of novel shades have been produced from coal-tar.
Red is obtained in various shades by using cochineal, safflower, lac-dye, madder, or logwood, with a tin mordant.
Purple. Until the last few years the dyer was dependent for his purples on orchil or cudbear, but he has now at his disposal the magnificent series of aniline, or coal-tar, colours, ranging from the most delicate violet, or ‘mauve,’ to the full crimson-purple, known as ‘magenta.’ See Purple Dye.
Yellow. The most important yellow dyes are made from quercitron, fustic, turmeric, arnotto, and French and Persian berries. For further information, see Bleaching, Calico-printing, &c.
DYER’S SPIRITS. See Tin Mordants.