Copper Sulphate

Copper Sulphate is used as a mordant for natural dyeing.  Copper sulphate can improve lightfastness and washfastness and can give different hues than other mordants. 

Adding a little acid to the mordant bath, like vinegar can aid in copper sulphate dissolving fully.  This is recommended by Jenny Dean. 

Copper Sulphate can bring out the blue and green colors of a natural dye.  Used with logwood, it can give deep, dark blues and it can intensify yellow colors or turn them green.  Copper is not usually used with red dyes.  Tin is better to use with red.  

Use 4-5% WOF (weight of fiber) per 100 grams of fiber to dye.  Dissolve in copper in hot water.  Let the fiber sit in the copper solution overnight, stirring occasionally to mordant, or you can heat the copper mordant solution for 1-2 hours, keeping it below a simmer.