[header] How to clean a cast [title] Wipe the outside of the cast with a damp cloth. [step] If you happen to get your fiberglass cast dirty, try wiping off the dirt, food, or other mark with a damp cloth. Make sure the cloth is only damp and not too wet. 
It should not leave any pools of wetness behind on your cast. [substeps] No matter if you have a plaster or fiberglass cast, you should never get your cast wet or submerge it into water, even if you get it dirty.