Campden release sulfur dioxide when dissolved in a liquid. They are added in small doses directly to fresh juices 24 hours before adding yeast. This is to destroy any wild molds and bacteria that may have been on the fruit. Campden Tablets are also used in stronger doses with water as an equipment sanitizer. You can use it to sanitize fermenting vessels, hydrometers, wine bottles hoses or any other glasses, metal, plastic or wood that comes into contact with your wine.