Tannins are naturally occurring compounds found within wood. They are carried to the timber surface by moisture, 'bleeding' through any finish, leaving a yellowish-brown stain. These stains are more noticeable on lighter coloured finishes, especially white. Treatex Stain Inhibitor is an easy to apply primer which is designed to help prevent tannins from migrating to the surface of the timber and causing unsightly staining. Exterior timbers with high tannin levels e.g. Oak, Idigbo, Teak, Cedar and Mahaogany) should be treated with Treatex Stain Inhibitor before being sealed with Treatex Classic Colour Collection.