Hello and welcome from the UK! I took up quilting when I retired and started with a jelly roll that I was given as a present. My grandmother quilted all her life and I used to help her wash and iron her fabric but the quilt shop included a note with my present advising me not to wash the jelly roll. I have since enquired and it is advised that precuts are not washed. I used a colour catcher to wash the lap quilt that I made from the jelly roll. It did shrink a little in the first wash but it has that nice slighltly wrinkled look that vintage quilt have. I have used yardage since then which I always prewash. Maybe others will be able to give you more expert advice.