In a large pot, place the natural fabric or yarn you would like dyed. Cover with water and turn the heat to high. Once boiling, turn the heat down to a simmer and simmer the fabric/yarn for 20 minutes, then turn off the heat.
Meanwhile, in another large pot, place the onion skins and enough water to cover them and allow them to float freely. Bring to a boil, cover, then reduce to a simmer. Simmer for one hour or until desired color strength is achieved.
Strain the skins from the dye and return the dye to the pot (or strain into another pot). Bring the dye to a simmer and simmer for 30 minutes.
Add the wet fabric or yarn to the simmering dye pot and simmer for 30 minutes longer. Turn off the heat, then carefully remove the fabric/yarn and place in an empty pot or container to cool down.
Once the fabric/yarn is cool enough to handle, rinse it well under cool, running water. Gently wring out the fabric/yarn, then place on a clothesline or rack to air dry away from direct sunlight.
See the full post above this recipe for more in-depth information on dyeing with onion skins. Enjoy!