Leather Tanning

While in China I had the opportunity to check out a leather tannery that produces cow and kangaroo finished products for many top brands' performance and lifestyle footwear.

This particulary tannery doesnt process the raw hides, but rather recieves them in "wet blue" form from local manufacturers or imports skins from Australia/New Zealand (kangaroo leather) or Europe (cow leather).

Click the Read More link below for more pics and info about the leather tanning process.






A "wet blue" is a semi processes skin, that is indeed, both wet and blue. The wet blue skin is a result of a chrome tanning process that is done after raw hide is fleshed and the meat and hair is removed and is designed to keep the skins soft and ready for further processing and free from bacterial growth.





Once the wet blue skins are recieved, they are first soaked in water to soften the skin. Then they go through a process called "semming" (not sure about the spelling of this, anyone have the correct term?), which pushes the water out of the skin, but keeps it soft to work with.

Skins are then "shaved" using a special machine that has a fine sandpaper like roller, which makes the skin (especially the bottom surface) more smooth and even.





After this, the skins are split to the correct thickness by being put through a machine that has knife edge which can accurately split the skin in crosssection.







Skins are then graded and measured. Measurement of processed skins is done using a special table that hasa computer controlled laser system which can determine the square footage of the particular skin and add the quantity to inventory.





After the wet blue process, the skins can then be drum dyed, to set a color or finish. The drum dying process involves putting the skins in giant drums along with various chemicals and dyes. A typical skin may go through 4-5 different 40 mintue cycles of dying with different chemicals for a 6 hour total process. Some special finishes can take up to 12 hours of drum dying.



Skins are then air dried for 2-3 days depending of the temperature and humidity inside the factory and can take up to 1 week in particularily cold or wet weather. the the above and below photos you can see the skins hanging from the ceiling on a conveyor system to dry.

Footwear Terminology

A to Z of footwear technical terms, construction methods, part names, and more.


Buff
To remove material by a sanding or roughing process. For example, EVA midsoles are buffed before assembly to help break the smooth surface for better adhesion to the upper.

Cement/Board Lasting
A lasting process where the insole board (carboard or texon) is inserted onto the last bottom and the lasting margin (excess) material of the upper is lasted onto the board and cemented to the insole board. Shoes of this type are usually more stiff and heavier.

Chemi-Sheet
A nonwoven reinforcement material that is impregnated with a chemical hardener that sets with application of heat or another chemical. Used commonly for counter or toebox reinforcement.

CM EVA
Compression Molded EVA. A foamed midsole material that offers good cushioning and compression set.

Collar
The opening area of a shoe at the top.

Colorway
A color/material combination.

Cosmo
An type of non-woven upper lining and reinforcement material used commonly on cross training and hiking boots that provides a stiffer (compared to Tricot) lining and support for the shoe.



Coutner
The back/heel of the shoe.

Eyelet
A hole through which you lace up a shoe.

Eyestay
The part around the lace opening (throat of the shoe). Can feature webbings, eyelets, etc.

FG
Firm Ground. Refers to football/soccer boots/outsoles designed for use on hard, natural surface.

Insole Board
The bottom part of the lasted upper.

Last
Anatomical representation of the foot for constructing a shoe

Lasting
The process of stretching the preassembled upper around the last, by machine or by hand.

Lasting margin
The upper material part that when lasted folds over the edge of the last onto the bottom, overlapping the insole board.

Midsole
The component of a shoe between the upper and outsole used to provide cushioning, fit, comfort and support.

Outsole
The bottom component of a shoe that provides grip and traction.

Overlay
An upper part which is over another part.

Padding
Refers to foam or other material usually inside the collar or tongue to add thickness/cushioning and improve fit.

PU (upper material)
PU upper materials usually use a thin layer of PU foam with a non-woven or fabric backing for reinforcement and strength.

PU
PolyUrethane. Synthetic (plastic) material with minute bubbles or cells and a skin like surface. Used for upper materials, and in a different form for midsoles or padding foam.

Pullover
A prototype sample for checking pattern and fit.

Quarter
The side of the shoe. Can have many subcomponents and parts.

SG
Soft Ground. Refers to football/soccer boots/outsoles designed for use on soft (wet) natural surfaces.

SKU
Stock Keeping Unit. A unique model/style/colorway/size. Commonly used to refer to a unique colorway. Ie, if there are 2 models each with 5 colorways, there are 10 SKUs total.

Slip Lasting
A lasting process where the insole board (usually canvas) is stitched around the last bottom edge to complete the upper. Usually used for more lightweight, flexible shoes such as running shoes.

SMU
Special Make Up. A special request by a customer (ie. distributor, retailer, etc.). It is normally just a different colorway of an existing shoe, but in some cases can also be a whole new shoe. There is not much more to it, really, just that it is requested directly. In some cases it may be part of a special marketing campaign (ie. one of those "exclusives" for Foot Locker you see), or might just be a product to better serve a particular niche covered by the market demographics, location, etc. (ie. maybe some country/market sells more brown colored shoes, but there are none in the main collection).

Stitch and Turn (seam)
A seam which is stitched to join two parts then flipped inside out so the stitch is hidden.

Toe Cap
Upper part on the toe, usually and overlay.

Tongue
Part which covers the top of the foot. Usually a separate component stitched inside the shoe at the bottom of the throat.

TPU
Thermoplastic PolyUrethane. Synthetic (plastic) material usually used for molded details and components on a shoe such as a molded eyestay, logo, counter reinforcement or waist stabilizer.

Tricot (a brand name, used to refer to a material, also Cambrelle)
Upper lining material, usually used on running shoes that is made from a sandwich of mesh type fabric, that allows a lightweight, breathable construction.

Turf
Refers to football/soccer boots/outsoles designed for very hard/round natural surfaces like dirt or turf and also synthetic grass surfaces.

Underlay
A part of a shoe upper that is under another part.

Upper
The part of a shoe created around the last.

Vamp
Area of the shoe/last on the front/top.