Abstract: A non-woven mat of inorganic fiber is disclosed having a substance which is lower at the edges of the mat than in the remainder of the mat. Apparatus for making such a mat includes: a source of a slurry of inorganic fiber in a liquid; a forming wire disposed to move past the source, the liquid passing through the forming wire to deposit the inorganic fiber on the forming wire; a mask across a part of the width of the forming wire to hinder passage of the liquid through the forming wire over the part, the effectiveness of the mask varying in the direction of movement of the forming wire past the slurry source.

Abstract: A non-woven mat of inorganic fiber is disclosed having a substance which is lower at the edges of the mat than in the remainder of the mat. Apparatus for making such a mat includes: a source of a slurry of inorganic fiber in a liquid; a forming wire disposed to move past the source, the liquid passing through the forming wire to deposit the inorganic fiber on the forming wire; a mask across a part of the width of the forming wire to hinder passage of the liquid through the forming wire over the part, the effectiveness of the mask varying in the direction of movement of the forming wire past the slurry source.

Abstract: A non-woven mat of inorganic fiber is disclosed having a substance which is lower at the edges of the mat than in the remainder of the mat. Apparatus for making such a mat includes: a source of a slurry of inorganic fiber in a liquid; a forming wire disposed to move past the source, the liquid passing through the forming wire to deposit the inorganic fiber on the forming wire; a mask across a part of the width of the forming wire to hinder passage of the liquid through the forming wire over the part, the effectiveness of the mask varying in the direction of movement of the forming wire past the slurry source.