When working on large Victorian Family Bibles, I use a paste wash to polish the leather rather than a wax or other polish which I find can be a bit greasy or unsatisfactory in some other way. This is a simple and effective method which I use on both the boards and the spine. If I am re-dying the leather, the paste wash is applied directly after the leather has been dyed. PLEASE NOTE: this method is not suitable for all books or all leathers. Some leathers, such as 18th century calf bindings, may well blacken irreversibly on contact with water. If you are unsure, please contact a professional binder or conservator.