I don't wash my fabrics on the most part and I get a perfect cut all the time. There is no need to pre-wash fabrics unless you are using flannel (because it shrinks too much) or a really red with a light color just in case. ALL fabric is washed at the dye houses, usually with Tide, before the industrial rolls are sent off to be cut into bolts. Now I have a 99cent/yd store near me that are end cuts from a dress making factory, etc. They do get great quilt & clothing fabrics in but the place is filthy so I wash that fabric before it hits my sewing room! I do notice a difference in cutting and everything with it having been washed.