IRON MORDANT ~ Mordant, Colour Changer, increased light fastness
Iron (Ferrous Sulfate) is used alone as a mordant, influencing Colours and to increase light fastness when used in combination with other natural dyes.
Iron is best known for shifting yellows into greens, keep in mind that this is not given and doesn't work with every yellow plant dye, in which case it will be more of a brown. it is used to increase light fastness for weaker plant dyes, bu it will always sadden and/or darken the colours.
When adding Iron to your dye bath start of with 3% and use it at the end of your dye bath or as an after bath. Allow to oxidize for 10 min for full colour development.
*If you like your colours darker, increase the Iron amount by 1-2% at a time.
**Leave for 10min than remove from dye bath - Iron will make wool brittle.