Linda and I ALWAYS pre-wash. As I remember it, people quit prewashing fabric back in the day when Harriet Hargrave came up with the idea that if you make your quilt with unwashed fabric, used a cotton batt, machine quilted it and then washed it, the quilt would look more antique. This is absolutely true. It helps to remember that this was back when machine quilting was not accepted in the quilt world and Harriet's idea was a very big part of what helped machine quilting become accepted.
But, if you are not after the look of an antique quilt, we think you should still prewash because:
- Fabric bleeds. How much it bleeds has a lot to do with the water chemistry where you are. There is a lot of variation in water chemistry.
- Fabric shrinks - and not all at the same rate. In my opinion it's better if fabric is shrunk before being sewn into a quilt.
- I think prewashed fabric behaves better for both applique and piecing. And, no, I don't add starch or sizing back into the fabric.
- Fabric directly off the bolt has chemicals in it in addition to the sizing - formaldehyde being the one I dislike the most. There are also pesticides sprayed on merchandise as it enters the US and that may be in the fabric as well. I much prefer to wash those chemicals out of my fabric before I store it in the closet or sew with it.
So, I wash with Orvus Paste. I add a color catcher (made by Shout) if I am worried about bleeding. I also have Synthrapol and Retayne on hand (the bigger guns for controlling bleeding). I wash in the washer in cold water. I dry fabric in the dryer. I fold it and put it on the shelf until I'm ready to use it. Then I iron it.