Old stains, dirt and other surface contaminants must all come off before a new finish can go on. Prepdeck stripper/cleaner, is a powerful, professional strength, high grade product specially designed to remove old solid and semi-transparent stains, water sealants, grade stamps, mill glaze and other surface contaminants from wood. Diluted it also makes a powerful cleaner for removing dirt and other surface contaminants. It's a fast, easy way to remove mill glaze so that new wood will accept a penetrating finish. It's also a great way of removing grade stamps. It really is 4 products in one, making it not only easy but also very economical to use.