Method and apparatus for folding a web of material

A method of pleating a web material to form a compressed rod of pleated web material for a filter rod of an aerosol-generating article, comprising:

• supplying a feed of web material from a supply apparatus;
• drawing the web material through a filter rod manufacturing apparatus;
• introducing a curved ridge into a central portion of a width wise cross-section of the web material as it approaches contact with an interior of a folding funnel, by drawing the web material across a forming surface of a former before the web material enters the folding funnel, wherein the forming surface contacts a central portion of the web material, in which the forming surface deflects the central portion of the web material from a line extending between where the web material leaves the supply apparatus and a center of an outlet of the folding funnel;
• and
• pleating the web material in the folding funnel to form a compressed rod of pleated web material;
• and, wherein the forming surface is provided with a textured surface.