All natural dyestuffs must be dissolved in a liquid before textile materials 

 can absorb them. Since water will not dissolve indigo, it must be dissolved 

 in another liquid. When indigo is combined with a reducing agent, a 

 compound is formed that will dissolve in an alkaline liquid. This process 

 turns the indigo dye liquid yellow. When wool and cotton are dipped 

 into this dyebath (known as the indigo, vat) they readily absorb the dye 

 in this yellow, reduced form. 



The dye is fixed on the fibers permanently by oxidation when the dyed 

 material is exposed to air. During this final step the blue color returns 

 and the dye reverts to its original insoluble form on the fibers. Repeated 

 dipping and airing of the material results in a gradual build-up of blue 

 color on the yarn or fabric; thus the skillful dyer can obtain almost any 

 depth of the blue desired. 



Both methods of indigo dyeing given below can be used by the home 

 dyer. 



Method 1: Indigo Fermentation Vat or Blue-Pot 



The fermentation vat or blue-pot is the oldest method of dyeing with 

 indigo. Bacteria that develop in the vat act as the reducing agent. Al- 

 though dyeing by this method is somewhat complicated, repeated dippings 

 result in a good, fast, dark blue on both wool and cotton if the vat is properly 

 prepared. 



When top-dyeing (see pages 107 to 109) wool with yellow dyes, mordant 

 (see pages 67 to 69) the material with alum either before or after dyeing. 

 Although treatment before blue-dyeing is not essential, the following 

 methods are sometimes used: 



For 1 pound of wool: alum mordanting (see pages 67 to 68) or soaking for 

 30 minutes in a solution of )^ ounce of washing soda in 4 gallons of luke- 

 warm water. Rinse thoroughly before dyeing. 



For 1 pound of cotton: alum mordanting (see pages 67 to 68) or boiling the 

 material for 30 minutes in a solution of ){ ounce of sodium hydroxide in 

 4 gallons of water. Rinse cotton thoroughly before dyeing. 



For each pound of wool or cotton, allow: 

 8 ounces finely powdered indigo 

 4 ounces wheat bran 

 4 ounces madder 



lJ/2 pounds sodium carbonate (washing soda) 

 4 gallons water 



Mix ingredients in a large vessel and keep it at about 85° F. for 5 to 10 

 days. This blue-pot should be stirred well each morning. When the mixture 



89 



285-390—68 7 



