Goodyear Welt Technique
The Goodyear welt technique of footwear construction is one that guarantees superior quality in the final product. The description of this technique, which follows, should give you an idea of why the production of this type of footwear is also much more intensive in terms of manual labor than other more basic techniques.
A Goodyear welt is a strip of leather that runs along the perimeter of a shoe outsole. The machinery used for the process was invented in 1869 by Charles Goodyear Jr., the son of Charles Goodyear.
"Goodyear welt construction" involves stitching a welt to the upper and a strip of preformed canvas like a "rib" that runs all around and bottom (known as "gemming") cemented to the insole of a shoe as an attach-point for the out sole or midsole (depending on the Goodyear welt variant). The space enclosed by the welt is then filled with cork or some other filler material (usually either porous or perforated, for breathability), and the outsole is both cemented and stitched to the welt.
The upper part of the shoe is shaped over the last and fastened on by sewing a leather, linen or synthetic strip (also known as the "welt") to the inner and upper sole. As well as using a welt, stitching holds the material firmly together.
The welt forms a cavity which is then filled with a cork material. The final part of the shoe is the sole, which is attached to the welt by some combination of stitching and a high strength adhesive like contact cement or hide glue. The result is highly valued for being relatively waterproof by minimizing water penetration into the insole and the relative ease of resoling as long as the upper remains viable. Welted shoes are more expensive to manufacture than those mass produced by automated machinery with molded soles.