After the quilt is done, I wash on the delicate cycle with warm water, very small amount of soap, with an extra rinse, and tumble dry low heat. I do not wash wall hangings. There is generally a small amount of shrinkage, maybe 2-3%, just enough to give that wrinkly comfortable soft puff and it seems to "set" the thread and fabric together. I prefer working with new fabric, I like the smell and feel of it! When it is washed first, it has to be ironed and the fuzzies need to be trimmed away, extra work! But if you swap blocks, they want it prewashed. However, if I were going to work with bold colors that were going to be next to a bright white, I would consider a prewash. I admit some people are concerned about fadding, but I have never had a problem with my fabrics, except when I have been working with old (50+ years old) fabric.