In brazing on pipe flanges (see sketch of four-way piece in Chapter XXIX (Worked-Up Pipe Bends, Breeches Pieces, Etc. Pipe Bends).) great care must be taken that both they and the pipe ends are properly cleaned. The flange should be slipped a little over the edge of the pipe, and the latter turned over on to the flanges to prevent the spelter from running through. Fireclay should be rubbed around the collar, and if the pipe is a brazed one, along the seam to protect from fire. To keep the heat on the joint a sheet-iron stopper should be placed in the pipe just above the flange, with fireclay rubbed around its edges. In brazing, great care must be taken to ensure the spelter running through the joint. While hot the brazed flange should not be treated too roughly, as the brass is very brittle in that state. When cold, the face of the flange should be cleaned up, and all superfluces spelter removed.