You should always check the tags for specific care instructions, but in general percale sheets can be washed in either cold or warm water (in moderation) without the use of fabric softeners or chlorine bleach, as these products can weaken cotton fibers over time. Percale cotton sheets should always be dried on a low heat setting and removed immediately after the cycle. Fold them, or smooth them out over your bed as soon as possible to help prevent wrinkles.