|In Sarah Veblen's class on Sewing with Wool, she has a "wool test" to see if your wool will shrink when steamed. You draw a 3" square on a piece of paper and then cut a 3" square of wool. The 3" piece should fit exactly within the square. Then you steam the wool and let it dry. If it still fits in the 3" square drawing, it needs no preshrinking. If it is smaller, you need to steam all of your yardage.
My husband came up with a method that is quicker than drawing if you have access to a photocopier. He photocopied the 3" piece of wool. When it came time to put his square of wool back on the page, it sat right on the image of the wool square.