This is a blog post on how to dye fabrics using indigo. This indigo vat is using hydro sulphate method. There 3 different methods to mix indigo vat using different ingredients. The goals of these ingredients are the same as it’s the deoxygenation process that is necessary to so that indigo turns and dyes the fiber. This post is a follow on from my previous blog post on setting the equipment for indigo dyeing. Click here to read further details.
How to dye fabrics using indigo
Indigo needs to be made into a paste before mixing it into the dye bath. otherwise, it would just be lumpy if it is not well mix not good when you want your look professionally done. To mix this paste using lukewarm water and some washing soda to mix it into a paste. I have mixed 25 grams of indigo powder with 1 tablespoon of washing soda. 25 grams of indigo powder will dye about 3 kilograms of fibers. It is a lot of fibres. Indigo is not water-soluble it is only soluble in alkali. Therefore, as a result of this special chemistry, indigo has got wash fast properties.
Prepare the indigo paste
Then prepare the soda solution this is to make vat alkaline. I have mixed about 200 grams of soda ash or washing soda with warm water first. This mixture is added to the indigo paste. This paste can last for a while as long as the ph (chemistry) is right.
Before you start preparing the indigo dye pot do get ready the fabrics ready to dye. I am passionate about fabric designing so I use the shibori technique. It is basically making patterns out of tie-dyeing, resist methods using all sorts of things that can be found at home.
Indigo dye pot
Now in a dye pot on a stove boil some water. Add the remaining soda ash solution. Mix the thiourea dioxide (100 grams) into a paste with lukewarm water. Slowly add till the ph on litmus paper shows 9-10.
In the dye pot with soda ash solution add the indigo paste till it is well mixed. Otherwise, it will look lumpy with some areas being more concentrated some less.
Then heat the mixture up till it is around 50 degrees Celsius. Maintain the dye mixture around this temperature. Depending on the use of the fiber this optimum temperature needs to be adjusted. For example, wool fibers can be dyed at a much lower temperature than 50 degrees Celsius. Otherwise, wool fibers will just boil and become felt.
Once the indigo vat is at the optimum stage add the fibers immerse them below the vat dye level to keep them dyeing. Bubbles will form as a result of chemical reactions. As once they are exposed or floating on top it will dye properly. Soak this for about 20 minutes. Maintain the temperature of dye at around 50 degrees Celcius.
Once the 20 minutes done, take the fabric out of the indigo vat and soak it in a bucket of water. This is to was out any patchiness of dye on the fabric. Do this slowly so as not disturb the bubbles. Once the fabric been washed, spread the fabric out and hang it up on a washing line. This so as to have an oxidization process changing from green to blue. This is the hallmark of indigo fabric dyeing. As always use gloves and dye indigo in an open-air environment.
Keeping indigo dye and shelf life
Do keep remnants of indigo dye in cool place away from children. I have stored my used indigo and use it again more than one month later. It does get tried/ exhausted you will find that the dye is not as strong. Just check the ph again add more soda ash to increase the ph level. This will be ok to dye till the indigo content mixture decreases. then it is time to remix another solution and start over again.