Step 1: Materials
n.b. The pool or hardware stores sell soda ash as sodium carbonate. Any pH upper will do! you want around pH 10 or 11 to fix "fiber reactive dye".
n.b. Arm&Hammer has a natural washing soda, sodium carbonate decahydrate, that contains water in addition to sodium carbonate, so use maybe 3 times as much.
Cold Water Fabric Dye : powder. $4 per little bottle (3 quarters (<--US currency) tall). 1 tablespoonish per shirt bag, will dye a second shirt, too. at least. I use Procion MX.
Some salt (tablespoon ish)
Some ziplock bags
Some gloves or plastic bags with rubber bands
A shirt or any kind of natural (cotton) fabric to dye.
Step 2: Soak Fabric in Soda Ash
1/3 ish cup soda ash powder
1 gallon water
in a zip lock bag.
You probably want to use enough water to cover the fabric.
Pour in the water, add the soda ash, close the bag and shake around, then add the fabric.
Let it sit half an hour.
This step matters. The soda ash prepares the fabric fibers to absorb dye. If you don't do this step the dye will fade dramatically in the wash.
Step 3: Soak Fabric in Dye
1 table spoon procion mx powder
6ish cups of water. luke warm.
a tablespoonish of salt
in a bag or bucket. shake or stir.
Consult packaging for exact quantities. Though experimenting will provide you with more flexibility in the future. The packaging doesn't know your goals, anyway.
I often resort to a large zip lock bag, but the mop bucket is a more environmentally friendly container if you're not going to save zip locks (if you do save them make sure to label them as NOT FOR FOOD, especially if you live in a coop like I do).
Fold/rubber band/tye fabric if dying with a pattern. I like to scrunch it up to get the crushed look in the pictures. No ties or rubber bands-- the key to crushed is to let the bag sit still and not move the dye around. The uneveness of the soda ash, salt and fabric layering and squishing will give the crushed effect.
On the other hand, for even color use a bucket and stir consistently. You can even put a large load in the washing machine.
Put the fabric, eg a shirt, in the bag/bucket. Add more water if necessary to cover the fabric. Seal the bag (if applicable) and squish out the air.
Step 4: Remove Fabric From Bag/bucket and Let Sit Overnight
Take out the fabric. Ring dry (back into the bucket if reusing). Put into a plastic bag and let sit over night. You might be concerned that your neat pattern will now dilute and disappear. In my experience the dye does not spread. This step does help strengthen the color.
Step 5: Wash and Dry
Hang dry. (You can use a dryer but why waste energy?)
n.b. - the dye will respond well to discharge paste (discharge pigment) and acrylic (screen) paint. There are many instructables on this topic, so if you've never tried this technique check it out. You can also screen/bleach/discharge before dying.