MORDANT MONDAY: Mordanting Cotton & Freezing Clothes

We get mordant questions all the time at Botanical Colors so why not create Mordant Monday??? Got mordanting questions? Email [email protected]

What is Mordanting?

Mordanting is the most important process of preparing fibers to accept color. Using a mordant helps to ensure the most durable and long-lasting colors. With the exception of indigo (as a vat dye, it does not require a mordant), this is not an optional step. However, there are many different mordants you can use. Deciding which mordant to use comes down to the types of fibers you want to dye and how much time or energy you wish to spend. The table we have on this page breaks down the different mordants that we sell and the advantages and disadvantages of each one.

YOU ASKED: I bought aluminum sulfate with the intention of mordanting cotton but I see on your blog that you don’t recommend it for cellulose fibers. Will it still work, just not as well?

KATHY ANSWERED: Aluminum sulfate was the first mordant for cellulose and you can use it for cellulose mordanting. The process is to pretreat with a tannin first, then soak in a solution of aluminum sulfate + washing soda and then dye. The results are excellent!

YOU ASKED: Do you have to mordant your fabric before you place it in the cochineal dye you have prepared. And if yes what do you use as a mordant. I want to eco print the fabric after dyeing it. I will eco print in an aluminum pot with water vinegar and a piece of iron in what is called a dirty pot.

KATHY ANSWERED: We recommend mordanting but I don’t have a lot of information on eco printing. The mordant can depend on the fabric content. If you are dyeing with a silk or wool, use aluminum sulfate. If you are dyeing with cotton, use aluminum acetate. We have instructions for both on our website under the ‘Learn’ menu. I have not heard about a dirty pot for dyeing but iron will shift the cochineal color from pink and red tones to purple and black tones

YOU ASKED: I am wondering if your aluminum triformate cold water mordant works as well or is comparable to aluminum acetate or works as well as a heated mordant process? I am intrigued by not needing to use heat but wondering if it gives fabric the same colour fastness.

KATHY ANSWERED: We found the best colors from Aluminum triformate were with using wool fibers as a cold water process. Aluminum acetate actually gave a deeper color on cellulose and it is already a cold water process.

YOU ASKED: I read on your website that wet mordanted fibers can be refrigerated. What are your thoughts on freezing them? The reason I would like to do it is to save the step of wetting out fiber before dyeing. I live in Colorado so I’m always thinking of ways that I can save water in the process. If I can put it in the freezer then I can mordant a bunch, and then just thaw out what I need!!

KATHY ANSWERED: I’ve frozen mordanted fibers and yarns before to good effect and you can also dry mordanted fibers and yarns and keep them ready for dyeing at a future date. Just know that the fabric kinda fuses together when it freezes, and I’ve torn it when I’m trying to pry it apart because I was too impatient to wait. So let it defrost a bit and then separate it. You can refreeze it and I don’t think it impacts that fiber or the mordant.