The first step for treating an ink stain on fabric is to rinse it well. The more pigment you can remove with running water, the more likely you will be able to remove the stain completely in the soaking and laundering stages. Hold the stain directly under cool running water for at least a minute, rubbing the area with your finger. Flip the fabric over and repeat. Continue for several minutes until the water runs clear. Do not wring it out, as that may spread the stain.
After rinsing, apply detergent directly to the stain and rub it in. If more pigment loosens, rinse again until the water runs clear. Repeat until no more ink will loosen. Allow the detergent to sit on the stained area for a few minutes, but don't let it dry. Spot treating should be followed immediately by hot water washing or, preferably, overnight soaking.
After a thorough pretreatment, soak the stained garment overnight. Depending on the fabric, choose one of the following: oxygen bleach, ammonia or non-chlorine bleach. Mix 1/2 cup oxygen bleach per gallon of hot water; oxygen bleach doesn't work as well in cold water so don't use it on fabrics that require a cold water wash. Instead, soak cold water fabrics in a solution of 1/4 cup of ammonia and 1/4 cup of laundry detergent to 1 gallon of water. Another option is to soak fabrics in 1/2 cup of non-chlorine bleach powder per gallon of warm water for 20 to 30 minutes. Never mix bleach and ammonia, as doing so creates toxic fumes. Follow the overnight soak with a machine laundering using heavy-duty detergent and the hottest water the fabric will stand.
If your ink stain is not on clothing, but on a surface such as a counter, table or floor, removal is very possible if the ink is still wet and you work quickly. Blot the ink with a paper towel -- don't rub it, as that will move the ink around and spread the stain. Rub the spot with a damp microfiber cloth or sponge. If the stain is still visible, moisten a cotton ball with non-acetone nail polish remover or rubbing alcohol and apply it lightly to the spot, followed by a water rinse. Always do a spot test in a hidden area before using any solvent on furniture or floors.