Is it necessary to prewash fabric before starting a project? There are two main reasons to do so.
All cotton fabric will shrink, some more than others. Flannel or homespun fabric will shrink more because the thread count (per square inch) is lower. The tighter the threads, the less they will shrink in the laundry. Some discount fabrics shrink more in one direction than the other, causing quilts not to lay flat. If you want to be sure your fabric will shrink properly, then wash and dry the fabric using a dab of detergent. Some quilters purposely skip pre-washing so their quilt will have the old-fashioned, puckered effect we see in old quilts. If you like this look, simply skip it.
Excess dye in the fabric can “bleed” onto other fabrics. Today’s products are of higher quality so this is less of a problem than years ago. In a trusted quilt shop environment (and not a discount store), the risk is low. However, there are certain colors that most quilters prewash; deep reds, purples and yellows tend to loosen in the wash, bleeding onto lighter areas. Using a product such as the Shout© “color catcher” will absorb excess dye and prevent bleeding.
Note that batik fabrics are already pre-shrunk since the dying process involves boiling water. Batiks are known for loose dyes, however, so the color catcher is recommended when laundering these fabrics or quilts made with batiks. If you want to be sure, prewash.
Information provided by Kelly Irwin, owner, Quilting Connection, 238 Main St. Ames, 515-33-3-48.