I have had to wash one of my quilts before sandwiching. Did it on gentle, no problem. One real dumb thing I did many years before I learned to quilt was to wash my Husbands Grandmothers quilt top. It sat in our closet for many years and I thought it was in need of cleaning. It turned out fine, lucky for me because the whole thing is hand pieced. I took it to our local quilt shop and had them sandwich and long arm it. The top is at least 100 years old. I would be afraid to wash it now!!!!