Goodyear welted construction is the traditional method of attaching sole to upper to achieve a mechanical join. The Goodyear desription takes its name from Charles Goodyear, the man who in 1869 invented a mechanised way of making the join. He therefore replaced the earlier completely hand sewn method.
The shoe’s unique quality is that the sole can be replaced many times, allowing the wearer to build up the highly desirable “patina” effect achieved through years of wear. This method of construction and the material component quality used results in shoes that can last up to 20 years, or longer, depending on the treatment and condition of the uppers.
There are 174 processes and 210 operations that go into making a pair of high quality Goodyear Welted shoes and thread is regarded to be one of the most important components.
Assembly starts by pulling the uppers over the last and tacking with nails; a canvas lip band of the sole is attached to the uppers (except for the heel area). The upper leather is tacked to the last and a few temporary tacks are applied to the front, before the upper edges are trimmed. The Goodyear Welt is sewn to the upper leather, through the rib on the sole; a wooden shank is added for strength and stability, and cork filling is put between the inner and outsole, to provide some cushioning for the foot.
Next, the outer sole is cemented to the rest of the shoe under high pressure; the sole is attached by adhesive and then shaped to fit the rest of the shoe. After this the thread is stitched to attach the upper to the sole. This can mean stitching through leather thicknesses of up to 2cms in order to hold the materials firmly together. Mass produced shoes are sewn by machine, but bespoke shoes are usually sewn by hand.
Hot vibrating irons are used to pound the edge of the sole, to give a hard, rounded, smooth and polished surface; the leather heel is nailed to the sole and the sole receives its final trimming. At this stage, the shoe construction is almost complete, but a number of finishing operations remain. The uppers and the welt are cleaned and polished; the soles are polished with wax and the last is taken out of the shoe. The shoes are then sprayed to give them a uniform shine and lustre, then after a final inspection, the shoes are wrapped, boxed and shipped to the retail shops.
It is essential the threads chosen have the correct technical properties to ensure good stitch-ability, consistent balanced lock and seam durability. Thread with inconsistent friction levels, or excessive extensibility, can lead to poor stitch balance which can cause premature separation of the sole during wear.