If you have mishandled washable silk, it can lose its sheen and become dull. You can restore some of the shine by following these steps. The fabric will improve but will never be quite the same.
In a large sink or bucket, add one-fourth cup of white distilled vinegar to each gallon of lukewarm water. Mix well. Completely submerge the scarf and swish around to completely soak the dress. Remove from the vinegar water and rinse several times in clean water. Do not wring!
Spread the scarf on a heavy clean white towel and roll up to absorb the water. Repeat with clean towels until most of the water is absorbed. Hang to air dry using a plastic hanger-no wood that can stain or metal that can rust. Do not hang over direct heat or in the sun.