Being a beginner and making my first quilt I learned a valuable lesson. I will never again mix natural fabrics such as cotton and synthetics like rayon together, not that you can't but you have to be very careful in the handling of these because of there different characteristics. I cut all of my pieces to the exact measurements and made precise quarter inch seams and after pressing the seams, looked at the match ups and was horrified at what I found. Some of the seams were off by at least 1/8 of a inch. After ripping out several seams and resewing and re ironing I finally figured out what was happening. I was using the iron on cotton setting and when I would iron the seam, the rayon would actually shrink and distort. I have sense ironed on synthetic and am more careful not to stretch the fabric when sewing. Seams are now coming out much neater. From now on it will be natural fabrics on natural and synthetics with synthetics.