I would soak them in Arm and Hammer baking soda and swish a little. You may want to add some vinegar or ammonia. Do this soaking for a couple hours or more. Then rinse well and soak again in Dawn and swish again. Then squeeze the Dawn out and rinse well. You may want to use a bucket of warm water to rinse. When you squeeze the rinse water out you should be able to see a color in the rinse water. Continue to do this til the water is clear. Good luck.