Mylands Oxalic acid is a cleaning agent which we sell in 500gram tubs. It is in crystal or flake form which makes it easy to disolve in water. It is used to remove or fade stains such as, water marks, rust Stains, ink stains, blood stains and can help remove existing stains before re-staining and/or re-finish. Mylands oxalic acid can also be useful in reviving the colour of light coloured timbers such as Maple, Ash and Satinwood. Oak is particularly prone to staining from contact with iron partials from steel wool or fittings leaving small speckles or larger stains. Mylands oxalic acid works very well in this situation.