DYEING 167 



surface. The microscope may bo thus usefully applied by the dyer to distinguish 

 whether a colour be the result of a mixed or a combined dye. 



The dyer should also be acquainted with the law of the simultaneous contrast of 

 colours. When the eye views two colours close alongside of each other, it sees them 

 differing most, in the height of their tone, -when the two are not equally pale or full- 

 bodied. They appear most different, when the complementary of the one of them is 

 added to the colour of the other. Thus, put a green alongside of an orange, the red 

 colour complementary of green being added to the orange, will make it appear redder. 

 And in like manner, the blue complementary of orange being added to the green, will 

 make it appear more intensely blue. 



It is not sufficient to place complementary colours side by side to produce harmony 

 of colour, the respective intensities having a most decided influence; thus, pink and 

 light green agree, red and dark green also ; but light green and dark red, pink and 

 dark greon do not ; therefore, to obtain the maximum of effect and perfect harmony, 

 the following colours must be placed side by side, taking into account their exact 

 intensity and tint : 



Primitive Colours Secondary Colours 



Eod . . . Green . Light blue; Yellow; Red 



Blue . . . Orange . 



Yellow orange . . Indigo . 



Greenish yellow . Violet . 



Black . . . White . 



Red ; Yellow ; Blue 

 Blue; Red; Yellow 

 Red; Blue; Yellow 

 YeUow; Blue; Red 



The mixed contrast gives the reason why a brilliant colour should never be looked 

 at for any length of time, if its true tint or brilliancy is to be appreciated ; for if a 

 person looks, for example, at a piece of red cloth for a few minutes, green, its comple- 

 mentary colour is generated in the eye, and adding itself to a portion of the red, 

 produces black, which tarnishes the beauty of the red. This contrast explains why 

 the shade of a colour, may be modified, either favourably or otherwise, according to 

 the colour which the eye has previously looked at. An example of the first instance 

 is noticed, when the eye first looks to a yellow substance, and then to a purple one ; 

 and as exemplifying the second case looking at a blue and then at a purple. 



The relations of dyeing with the principles of chemistry constitute the theory of the 

 art, properly speaking ; this theory has for its basis the knowledge 



1st. Of the nature and properties of the bodies which dyeing processes bring into 

 contact. 



2nd. Of the circumstances in which these bodies are brought together, facilitating 

 or retarding their action. 



3rd. The phenomena which appear during their action ; and, 



4th. Properties of the coloured combinations which are produced. 



The first of these generalities embraces a knowledge of the preparations which stuff 

 necessarily undergoes previous to dyeing, and also the preparations of the dye-drug 

 before bringing it into contact with the stuff. 



The operations to which stuffs are subjected before dyeing, are intended to separate 

 from them any foreign matters which may have become attached, or are naturally 

 inherent in the stuff. The former are such as have been added in the spinning, 

 weaving, or other manipulations of the manufacture, and are all removed by steeping 

 in an alkaline lye and washing. The second are the natural yellow colouring sub- 

 stances which coat some of the various fibres, both vegetable and animal ; and the 

 chlorophylle, or leaf-green of vegetables. The removal of these is generally effected 

 by boiling in soap and alkaline lyes. A weak bath of soda, in which the stuff is 

 allowed to steep for some time, and then washed in water, is generally the only pre- 

 paration required for wool, in order that it may take on a uniform dye. 



To remove the gummy or resinous matter from silk, it requires boiling in soap-lye ; 

 however, its removaf is not essential to the stuff combining with the dye, as silk is 

 often dyed while the gum remains in it, in which case it is only rinsed in soap-lye at 

 a very moderate heat, to remove any foreign matters imbibed in the process of manu- 

 facture. 



Vegetable fibre, as cotton, has such natural resinous matters that retard the re- 

 ception of the dye removed by boiling, either with or without alkaline lyes ; but the 

 natural dun colour of the fibre is not removed, which from the laws of light and 

 colour already referred to, would interfere with the production of bright light tints ; 

 under these circumstances, the natural colour of the fibre has to be previously removed 

 by bleaching : for which see the article, BLEACHING. 



The necessary preparation of the dye-drugs within the province of the dyer, is to 

 obtain the colour in a, state of solution, so as to allow the fibre to absorb it, and to 



