Reverse tye-dye. 2 parts bleach to 1 part water in a spray bottle. Cut out design of your choice on thin craft foam (stuff used to make those kiddie sun visors) and lay out on shirt. Spray edges of design. Carefully remove foam. Rinse with cold water when the bleached area is at the desired lightness. Wash separate from other clothes the first time. Works best with dark T-shirts.