Through the study of the remains of cementation furnaces in the Bristol area (south west England) active until the beginning of the 20th century, the author describes the techniques of brass manufacture, making comparison with similar brass mills still standing in saltford. In the appendix: report on the examination of blue material from industrial remains at Warmley; composition of Bristol brass; unfinished brass shells from the river Avon, Bath. Illustrations, bibliography. -- ICCROM