I discovered that prewashing the batting not only shrank it a bit, but also made it thicker. I got a thicker quilt, but less crinkly, when I prewashed my cotton batting. So now I decide if I want a thicker, less crinkly quilt, or a thinner, very crinkly quilt? That determines if I prewash the batt or not. I always pre-wash the fabric, unless it's small pre-cuts, to get rid of the chemicals in it.