Mordant Monday: Mordant after Dyeing?

YOU ASKED: Can I mordant after dyeing?

I just returned from India, dyed a number of silk scarves and was told the I can mordant them after they have been dyed. I have been trying to find more details but have only read on your site about post-mordanting something that has already been mordanted?

KATHY ANSWERED:

There’s actually a technique that is practiced in Japan that is referred to as “middle mordanting”. The process is to immerse silk fabric in dye, then transfer it to a mordant bath, and then return it to the dye bath. It definitely deepens the shade of the color, and you can repeat the process and continue to build the shade. Catharine Ellis and Joy Boutrup have detailed instructions in their book The Art and Science of Natural Dyes on page 126, and in their Studio Formula Set on page 46.

In The Nerd’s Guide to Mordants workshop at Sanborn Mills Farm last summer, we tried this technique using cochineal dye on silk crepe de chine. At first, the silk fabric in the cochineal dye was a sickly pink, but after immersing it into aluminum potassium sulfate and then back into the cochineal bath, we were rewarded with a beautiful deep shade! I’m returning to Sanborn Mills Farm in NH and will be teaching this workshop again April 9-13, 2025.

What I really liked about this approach is that it’s fun to see the color develop right before your eyes! Note: we used a slightly modified process than Catharine and Joy have in their book.

Our recipe

We used a piece of silk crepe de chine that weighed about 50 grams

Cochineal dye@ 3-5% extract, or 5-7% if using cochineal insects on the weight of fiber (wof). We used 5% wof (2.5 grams) of cochineal extract.

Prepare a dye bath and dissolve the cochineal extract in a little hot water, then add to a container of room temperature water. We used about 2 quarts (2 liters) of water.

Measure aluminum potassium sulfate at 20% wof. We used 10 grams of aluminum potassium sulfate.

Prepare a mordant bath of room temperature water. We used about a quart and a half of water and used hot water to dissolve the mordant, then added it to the container of water and stirred well.

Dampen the silk fabric and immerse it in the cochineal bath. Move it around so that it is evenly saturated for about 10 minutes.

Remove it from the dye bath, squeeze it out gently and immerse in the alum mordant bath. You will see that the fabric starts to get a little more saturated and take on a deeper shade. Move the fabric in the mordant bath for 10-15 minutes. Remove from the mordant bath, squeeze gently and re-immerse in the cochineal dye bath. You should notice a deeper and richer shade change. Continue moving the fabric in the cochineal bath for 15 minutes.

Repeat this process: remove the fabric from the cochineal bath, squeeze gently, and put it back into the mordant bath. After 15 minutes, add it back into the cochineal bath. I’ve left the fabric in the cochineal bath for over an hour to deepen the shade even more. Just make sure that the fabric is not bubbling up above the surface of the dye bath or you may get uneven areas.