Abstract: The present invention relates to methods for removing carbon from a char product that is formed by heating a silica-containing rubber compound in an inert atmosphere or under vacuum. The method includes heating the char product in an oxidising atmosphere to remove the carbon material leaving a silica-containing product. The methods are particularly applicable to vehicle tyre rubber compositions. Silica-containing products obtained by these methods and rubber compositions incorporating such silica-containing products are also aspects of the invention.