S8 



then be only necessary to immerse the things to be dyed in a 

 solution of the colouring material. Unfortunately in this case the 

 dye is not permanent, it is readily washed away by water ; it there- 

 fore becomes necessary to impregnate the cloth with some substance 

 which has an affinity for both the fibre of the fabric and the 

 colouring matter, — something which will, in fact, bind them 

 together. Such substances are termed " mordants." It is essential 

 that a mordant should be capable of forming an insoluble compound 

 with the colouring matter, so that when the coloured compound is 

 precipitated in the fibre of the material it cannot afterwards be 

 washed out. A solution of logwood and alum was shown precipi- 

 tated by ammonia, and it was explained that the formation of this 

 precipitate in the fibre of the several textures constituted the 

 mystery of dj'eing. It is, of course, necessary that the mordant 

 should be in a soluble form when applied to the fabric, so 

 that it may readily enter into the intercellular spaces. The 

 mordants most generally employed are salts of tin, iron, and 

 aluminium. 



Of the vegetable matters used in dyeing, the following are the 

 most important : — Alkanet: this was used b}' the ladies of Rome as 

 a pigment for the face ; and is still employed in the theatrical world. 

 Archil, well known to the ancients. Braom. a yellow dye, which 

 was used by the Celts. Madder, still used largely ; formerly by the 

 Eg3rptians, who dyed mummy-cloths with it ; and by the Romans. 

 Nut'galla, for dyeing black. Wood: Julius Caesar states that the 

 Britons of his day stained their bodies with the blue dye of the 

 woad. Indigo is obtained from woad, which is largel)- cultivated in 

 Lincolnshire. Seeds of the Pomegranate, mentioned in the Old 

 Testament. Logwood. 



Of the mineral matters used, sulphate of iron, with or without 

 a native alum, and sulphate of copper, are the most important. 



Cochineal is an animal dye. About 1560 it was discovered 

 that by using a salt of tin with cochineal, a colour could be produced 

 which far sm-passed in brilliancy any of the ancient dyes. In 1667 

 logwood and indigo began to be employed in Europe. An Act of 

 Parliament was passed in Queen Elizabeth's reign, which denounced 

 as a dangerous drug the dye called indigo, which was stated to be 



