It's your cottons that are shrinking and making your work look messy, polyester is plastic, it won't shrink. But if it gets hot enough, will melt. That's why you can't use a hot iron on any garments made of the material. They all say, use a cool iron (you might as well use none! LOL) Whenever I wash a table runner, wall hanging or place mats, etc., they are hung to dry. People ruin more beautiful things using dryers. What's the fixation with dryers?