FAQ THE SHEETS WHAT IS PERCALE? SEE ALL QUESTIONS WHAT IS PERCALE? Percale is a weave fabric that is incredibly breathable. Percale sheets provide cool, crisp comfort that only gets better with time — which is why we chose this fabric for our Casper sheets. YOU MAY ALSO LIKE What is Supima® or Pima® Cotton? Can I review the sheets? Do you make custom size or RV mattresses?