For 1 lb. of fiber or fabric you will need the following:
- ½ oz Indigo for light blue or 1-2 oz for darker blues.
- ½ oz Dharma Dyehouse Color Remover (Thiorea Dioxide) or Sodium Hydrosulfite
- ½ oz Soda Ash
- 2-3 gallons of water
Important: Before starting any dye project you should always do a test run on scrap fabric first. Dyeing with Indigo is a process with many variables, and as with any new process, common sense dictates that you always TEST FIRST if you have something specific in mind. If you are more flexible, you will be enthralled with the range of beautiful traditional blues you can get. You can also overdye Indigo dyed fabrics with other natural dyes to get other colors. If you have a chemistry student in the family, and they know how to handle chemicals safely, the chemistry of getting to the blue cloth makes for a very interesting project.
Pour powdered indigo into 1/4 cup hot water. Stir until dissolved. Pour dissolved indigo into a large pot of water. In a separate jar, dissolve the Soda Ash in some warm water. Add the Soda Ash solution to the Indigo and stir. This increases the PH of the dyebath to prepare for "reducing" the dye and making it soluble in water. Add half (1/4 oz) of the Dharma Color Remover and stir gently. Heat to between 120°F and 130°F continuing to stir gently. The liquid should appear yellow or yellow-green and may even have a bit of a scummy appearance somewhat like a witch's cauldron; this is okay. Let the mixture stand for 20 minutes. If the water appears blue, too much oxygen has entered the dye bath and you will have to add more Dharma Color Remover into the bath and stir GENTLY to reduce the indigo. To get the best tones from the indigo, you should avoid letting too much oxygen get into the pot as it causes the dye to precipitate out of solution. This means you must work much more slowly and gently than with other colors. You may find it helpful to tie a line of thread to one corner of your fabric before immersing it in the dye as this will make it easy to fish your fabric out of the pot without stirring excess air into the dye bath.
After the dye has steeped for 20 minutes you may then add your fabric. The wet, pre-washed fabric can be compressed into a ball, lowered into the dye bath and then allowed to expand. Again, stir GENTLY. The first fabrics will only need to be immersed for a few minutes to absorb the maximum color while fabrics added later may need to stay in for 5 to 10 minutes. When the fabric is removed from the dye pot, it should first look yellow-green and then turn blue after it comes into contact with the oxygen in the air. This is where the dye is "oxidizing" again, and becoming once more insoluble in water, which is what makes it stay "trapped" in the fibers of the fabric. You can also re-do the dyeing more than once - successive "dippings" and oxidizing yields deeper and deeper blues, and is the best way to get dark color. If instead you try to get a dark blue by one but much longer and more concentrated dyebath, like you might with other dyes, most of it will just wash out or rub off. When you have reached your desired depth of shade, you need to wash out the chemicals and excess Indigo. As with all dyes, wash out the fabric in Hot water and Synthrapol or Dharma's Professional Textile Detergent to get out the all of excess dye. This is a very important process, or the dye will "crock" or rub off on you and you will look like you are trying out for the "Blue Man Group". One thing that helps to have less dye come off and less fading in the future, is after one brief rinse, to put the fabric in a hot soak with Dharma Dye Fixative or Retayne for 1/2 hour (1 oz fixative per lb. of fabric). This causes more of the Indigo to stick to the fabric. Then do the Synthrapol wash and you are good to go. The fabric will fade less with successive washings also.
To get the best, most even dyeing results it will be easier to work outdoors and with another person. When the fabric is removed from the dye bath, you can hang it, or a fun thing is to take the cloth and stretch it tautly from all four corners (like when folding a sheet) at a vertical angle so the excess dye can run over the surface of the fabric. Tilt the fabric back and forth so that the dye runs in all directions over the fabric; this step is not a requirement but without it the dye may strike unevenly and the result can look like a cloudy sky with lighter and darker areas of blue. After a few minutes of exposure to the air and the desired blue hue has been achieved, the excess dye can then be rinsed off. If your color has turned out unevenly you can repeat the dye process to help even out the color. Fabrics that are tied or clamped as in Tie-dye or Shibori look fantastic when dyed with Indigo.