A method and apparatus (1) for treating a filter (2) for filtering particulate matter from 5 exhaust gas and a treated filter (2) are described. A reservoir (3) containing a dry powder (4) is provided. A vacuum generator (6) establishes a primary gas flow through a porous structure of the filter (2) by applying a pressure reduction to an outlet face of the filter (2). A spray device (7) receives the dry powder (4) from a transport device (8) and sprays the dry powder (4) towards the inlet face of the filter (2). A controller (9) is configured to control 10 operation of at least the vacuum generator (6) and the spray device (7). The dry powder (4) comprises or consists of a metal compound for forming by thermal decomposition a metal oxide.