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 is a sateen weave? How long will the sheets last? What are the dimensions of the sheets? What is the warranty for Birch Mattresses? What materials are in the Birch Plush Organic Mattress Topper?