Soda ash or washing soda
Fibre reactive dye
Non-iodized salt (kosher, sea salt or pickling salt)
Cotton T-shirt (pre-washed with detergent)
Rubber gloves 

1. Scrunch up the T-shirt
2. Sprinkle different colours of dye
3. Add warm water over the dye
4. Sprinkle soda and salt over the dyed areas
5. Scrunch up the shirt and allow to set