This was once a baby blue wool blanket. The leaves were soaked overnight in rust water before the fabric was bundled and simmered overnight in a slow cooker.
How to make rust water? There are two ways.
1. Iron Oxide: Ferric (FE2) is known for its rusty deposits on other materials.
Find discarded bits of metal that have gone rusty. For example squashed bottle caps, old bike chains, tin cans and the like. put them in a bucket of water and soak until the water turns a rusty brown. Vinegar helps to speed up the process.
2. Ferous Sulphate: (FE3) is a clear water soluble iron
You can buy Ferris Sulphate from your local hardware or garden shop. Measure out a few teaspoons into a bucket of hot water and let sit overnight. This is also the same compound that humans take as a iron supplement.