What materials are the sheets made from? February 18, 2021 18:17 The Birch sheets are made from 100% organic cotton and include a 320 Thread Count with a sateen weave. Related articles What are the different mattress sizes and dimensions? How is my Birch Mattress shipped? How long will the Duvet Cover last? What is a mattress pad and how is it used? Why do I need a mattress protector?