Hi Aaron, In the lab we extract rose bengal from bacterial slides using acidified 50% ethyl alcohol. On a shell you can't use the acid of course, but 50% ethyl alcohol is probably your best bet. For some reason, the 50% solution seems to work better than either stronger or weaker solutions. Pure ethyl alcohol won't extract the dye at all. You could also add a bit of ammonium hydroxide (household ammonia) to the alcohol solution. Regards, Paul M.