Red Limestone ('bpoon daeng' in Thai) is used to crisp vegetables and in batters for fried foods and pastries.
To make slaked limewater mix 2 tablespoons of limestone paste with 5 cups of water in a container, stir well, and let stand until the lime crystals sink to the bottom. Pour the clear liquid out and use to soak young potatoes to make the flesh cripsy before cooking.
According to Thai cookbook author and cooking instructor
