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.