Part used: husks
Color range: browns, chocolate, almost blacks
Active dye component; juglone
Mordant: none needed
Light fastness: excellent
WOF: 50-100%
Cold dyeing: yes
Hot dyeing: yes
Low Impact Method: no (unless you really grind the hulls to a powder)
 
The hulls of the black walnut fruits are known for their potent dye. Traditionally used in ink making, and dyeing fabrics deep browns and almost blacks in combination with iron.
Like all hull and barks, soaking before the dye process makes the most of your dye stuff. 
 
Walnut husks have a lot of tannin, which makes them a good candidate for a dye blanket when you want to create that nice deep background colour on your eco printing project.
 
Always soak bark and roots overnight before heating. Use a dye bag when dyeing wool or the bits will get stuck in the fibers. Heat slowly to below a boil, boiling may dull colours. No mordant needed but alum will intensify the dye results.
 
Renewable and sustainable dye source from the USA.