The optimal way to wash removable cushion covers is with cold water, and avoid harsh scrubbing - in a machine this would include adjusting the cycle settings accordingly and using a dye free detergent. Keep your covers zipped to avoid tangling. Most of the the times, a stray strain can be cleaned up by blotting with a soaped, damp paper towel - never scrubbing. Dry naturally instead of using a machine dryer, but avoid harsh sunlight as that may cause fading.