372 The Art of Dyeing, 



Solution of i^otash forms a yellowish spot. If the whole 

 piece is immersed in a weak solution of potash the shade 

 becomes light. 



Lime water has no action. 



Ammonia renders the colour brown. 



Vinegar produces spots of a light brown colour. 



Lime juice forms light brown spots which ammonia does 

 not completely remove. 



Both tin mordants discharge a light brown. 



Solution of chloride of lime, when printed on it, has no 

 action. It produces a scarcely perceptible brown shade. 



Remark, — In the use of this dye, a gummy matter is 

 formed in the solution, by which it will be weakened. It 

 is necessary, therefore, to employ an excess of willow bark. 

 With birch bark a similar colour is obtained possessing 

 analogous properties. 



2. BLUE FROM ALUM AND COPPER MORDANT WITH LOGWOOD. 



The method of mordanting for logwood blue has been 

 already given. The blue is darker in proportion to the length 

 of time that the mordanted calico remains in the copper 

 mordant. An excess in dyeing is proper for giving a clear 

 colour. A greater proportion of bran is also useful. The 

 following proportions may be used : — 12 lbs. mordanted 

 calico, 3 lbs. logwood, and 30 lbs. bran. 



The dyeing solution, which, after the dyeing, still con- 

 tains much colouring matter, may be again employed for 

 the production of the same colour, while yet logwood and 

 bran are added. 



The dyeing should be operated slowly, and the tempera- 

 ture of the solution should not exceed 167°. If it is raised 

 to a boiling heat a violet hue is produced. When 32 lbs. of 

 cloth are boiled with 1 lb. soap in 2000 lbs. water the dye 

 takes up soap and becomes darker, and the solution of soap 

 becomes only slightly reddish. If the proportion of soap 

 is increased, it acts upon the dye, and the calico becomes 

 paler as with 4 lbs. soap to 32 lbs. cloth. 



PROPERTIES OF LOGWOOD BLUE, 



This colour is, as formerly stated, pretty permanent to 

 light and air in consequence of its containing copper. 



