This would fall under the category of what not to do. Lesson One: Don't try to prep scarves for a class while doing nine other things. Last week I was putting scarves through the iron pot in order to prep them for my last class of the year. The cauldron I use for this is my son's Dutch oven from Boy Scout days. It holds about a gallon of water with a splash of vinegar and three scarves comfortably. I bring the water to a boil, put in the scarves let it simmer for about 15 minutes. Then I turn off the heat and let it set until it is cool. To get ten scarves done takes about a day, and since three fit at once, you can probably see where I am going with this. After 3 batches, there was one lonely little scarf left. It was time to start dinner and as I was putting the last one in I thought to myself "Remember to set the timer on your phone, or you will forget this poor little loner and boil the pot dry." Somewhere between thinking that and deciding to go get a squash out of the root cellar, the timer never got set. When I remembered this was halfway through dinner. You can imagine what came out of my mouth. My husband is used to this sort of thing and went on about finishing his meal. I, on the other hand, went flying across the yard to the studio stove. Amazingly enough the pot had not boiled completely dry, but was very close. The water that was left in the bottom was very, very rusty. The poor scarf had not actually burned yet, but for all practical purposes, might as well have. Needless to say I needed a re-do on a scarf for the class, which I had the sense to leave until the morning. I pulled the now extremely rusty scarf out and hung it up in the studio. I figured after being heated to that extent and exposed to that much rust it was probably useless. While some metal exposure is useful as a mordant, too much heat and too much metal exposure is not good for any fiber. It makes silk stiff and brittle. But, being the fugal soul I am I decided to go ahead and steam some leaves in the thing and see what happened. I used maple and filbert leaves, which you can see from the picture made wonderful black prints. I can't sell this one since I can't stand behind it from a quality standpoint, I am just going to keep it and look at it for now. Even though it feels pretty good now, in fairly short order it could develop brittle spots that would basically crack, making holes in it. I would only wear it if I were wearing a turtle neck, or use it as a belt or something as too much metal exposure is not good for us either. After enjoying the beautiful rich blacks and deep greens for a bit, I may decide to cut it up and do other things with it, we will see.
To use rusted water as a mordant in the right way, you would take some rusty objects and put them in a quart jar of water with a splash of vinegar. Put the lid on it and let it set until the water looks rusty. To mordant the fabric put about half that rusted water in a gallon of water in a neutral pot, bring to a boil, put the fabric in and simmer for about 15 minutes. Turn off the heat and let it cool. Take a look in there every once in awhile and pull it out when you think it is "rusty enough". Proceed with eco printing and you should get similar black prints without degrading the fabric quite as much as I did.
Set the timer. ALWAYS set the timer.