Intergrain UltraPrep Timber Cleaner is a high strength cleaner that restores grey, rust or tannin stained, mould or mildew affected timber to a clean appearance suitable for coating.UltraPrep Timber Cleaner is also used to clean and prepare new timber for coating by removing the dirt, tannins, oils and other contaminants that are present.Intergrain UltraPrep Timber Cleaner has a non-bleaching formula and contains oxalic acid, which is a naturally occurring, bio-degradable organic acid.