Abstract: A method is disclosed for maintaining continuity in a manufacturing process employing one or more webs provided in the form of shorter raw material webs in which the raw material webs are spliced together end-to-end as the preceeding web of the same material is depleted, and those web portions containing splice material are detected at a later stage of the process by a microwave detector. A microwave detector is provided in the form of a slotted microwave cavity through which the web may be continuously passed to detect the splicing tape in the web.