What is the best way to clean alginate trays that have dried alginate and dental stone embedded in them?

Once alginate or stone is dried and stuck to metal alginate trays, it can be very difficult to remove. There are products available that chemically remove residue from trays. A new product that got a 5+ rating from our Clinical Consultants is Green Envy Tray Cleaner (Whip Mix Corp.). It is environmentally friendly with no harsh chemicals, has a neutral pH to help prevent corrosion or damage to the trays, has a pleasant citrus odor, and is gentle on the skin.