Brown spots on old fabric is usually caused by it coming in contact with paper or wood, which is acidic. As a quilter, I have heard that spots can be successfully removed from washable fabric by soaking in Oxyclean. A good way to store fabric items is in a pillowcase, never in plastic bags or in a gift box or cedar chest. Hope this helps. Kate
I found that oxiclean took the stains out of some vintage pillow cases I had stored in a closet. Because I was concerned about the age of the fabric and the handmade lace I was careful to not use really warm water. Everything came out really well.
Before you use Oxyclean be sure to test the material first on an inconspicuous spot. I ruined some fabric last year with Oxyclean because I didn’t test it first.