Place ginger slices into a saucepan. Cover with cold water, add a pinch of salt, bring to a boil, reduce heat and simmer for 30 minutes. Then drain the ginger, rinse under cold water and drain again. Repeat this process three more times, each time using cold water and another pinch of salt. Return ginger to saucepan, and add 4 cups of water and 1 cup of sugar and then bring to a boil. Lower heat and simmer until a thick syrup coats the ginger (1 1/4 hour). Sprinkle a 1/4-inch layer of sugar in a small baking dish. Using a fork, transfer ginger slices to sugar, turning to coat them well. Cool coated slices on a wire rack for at least an hour. Store airtight