If you have a grass stain first pre-soak the stain in cold water for at least 30 minutes. Rinse. Pre-treat with detergent. Wash using detergent, hot water and bleach safe for fabric. On acetate and colored fabrics, use 1 part of alcohol to 2 parts water.
For grass stains use cold water and no soap. Alcohol or ether may be used if the material is unwashable.
