Thank you for your responses! I don’t think anything will lighten this fabric, I even soaked a piece in undiluted Clorox for 30 minutes and it didn’t change a bit. Oh well. I’ll go to plan B and use some of the light shades I have of the aged muslin and I found a few sites where I can buy more of the light shades. It’s an older fabric line so they don’t have all the lighter shades but there’s enough so that I can have a little variation. And I may try tea dying some to give a more vintage and varied look. I’m a Barbara Brackman fan and was very happy when I found one of her older lines at the estate sale.
It’s been so hot here that I haven’t been able to even look at my quilting or fabric. My sewing room is in a finished part of the attic. There’s no air-conditioning and with the south facing window it’s brutal up there when the weather is like this.