2 cups of DAWN and 1 cup of rubbing alcohol. I used the good ziplock bags- one inside on another with one zipper side down inside the other with the zip on top. Loosely wrap in a thin dishtowel or into a old pillow case. Mine started leaking after about a year so I just poured it into new bags. It freezes nearly solid but becomes maleable quickly. Don't use on bare skin without a cover- they are really, really cold.