I started 3 yrs ago and I pre-washed. Then I made a quilt with 4" charms I bought on ebay and didn't pre-wash those. I notice the fabric was much easier to work with since it had the original fabric sizing (sp) on it. Now I never prewash. I will sometimes rinse the extra dye out of some batki reds if they dont pass my bleeding test (put a snip of fabric in a cup of hot water).