Monday, August 10, 2015

Ecoprint with cotton: (pre)mordanting the fabric



As Cotton is a difficult fabric to get your leafprints on , we need to (pre)mordant the fabric.

Because most commercial fabrics have been starched or coated, it is always best to scour the fabric using a hot water wash or by soaking it a few hours or even a day or two in a bucket of water with a tablespoon of kitchen soda or soda-ash .

“Scouring” is the deep cleaning of fabric or fiber. Scouring helps assure even color and good penetration of the dye. Cotton, in particular needs scouring, even if it is brand new from the fabric shop because most commercial fabrics are coated with waxes and oils

After the removal of starch, the cotton fibers have to be prepared to allow the dye to bind. This pre-treatment is known as "Mordanting". The mordanting process also improves the light and color fastness, which is an issue with natural dyes as compared with synthetic dyes like Dylon or Procion MX. Mordants come in many varieties but most are not good for people or the environment. In the interest of environmental sustainability and our own health, we will work with alum, and/or soymilk only.

There are different possibilities for mordanting, I will share the ones I've tried. Please remember, there are many ways and stuff to use, I just share my own experiments, and I am still experimenting with other mordants too! There is not one perfect road, it is just 'trial, error AND succeed' at the same time.

Cotton, linen and ramie are composed of cellulose fibers. These fibers need a protein rich or alkaline solution as a mordant. Good results are achieved with a mixture of one tablespoon of alum and one tablespoon of soda per 3 liters of hot water or a mixture of 100 ml. soy milk and one tablespoon of soda in 3 liters of water. This solution has a long shelf life and is reusable! The fabrics should be soaked in this mordant solution for a few hours or up to few days.

Mordanting with iron (II) sulfate
You can place your fabric in a basket full of water and one or two teaspoons of alum, or, a cup of soymilk and leave it for a day. Afterwards, you can have a second mordant bath, which I often use, the Iron (II) sulfate (again one teaspoon in a basket of water). Remember, if the iron (II) sulfate is already in the fibre, it can easier start its printing process.

Oak galls

Another way to prepare your fabric in a natural way, is to soak the fabric in a tea, drawn from oak galls, with or without a teaspoon of iron (II) sulphate added.



Some people premordant the fabric again with alum after this second bath, but I never tried it as I am happy with the current results ;-). No rinsing of the fabric in between, just let it rest in the bath.

Leave if there until you are ready to start wrapping, wednesday we'll discuss the leaves and friday we start boiling!!

4 comments:

  1. Thank you so much for those precious informations ! i discovered the technique only this week, and would never have thought i might use soy milk :) long to read your next post !

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  2. Thank you for such an indepth explanation. You are so sharing. I am eager for the next post.

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  3. Really informative posts. I do have a question about the soda that you use with either the soy milk or alum. Is it soda ash?

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  4. Yes I use soda ash, but when you want to use cleaning /crystal soda, just take three spoons instead of one. There is no difference only in volume.

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