Leather comes from the skins and hides of animals and tanning is the process of treating them to make the skins more durable and less susceptible to decomposition – in other words, to become the leather we love. Traditionally, tanning used tannin, an acidic chemical compound from which the tanning process draws its name.
Obviously the first part in making leather is separating the skin or hide from the animal. This normally occurs when the animal is slaughtered for meat or other uses, so leather can be seen as using waste products that otherwise would have been discarded. After skinning, the tanning process has to start within 36 hours. Alternatively, skins can be cured in order to stop them from rotting. The proteins in the skins would normally be subject to bacterial growth, but by removing as much water as possible during the curing process, stops this from happening.
The hides go through a series of processes collectively known as the beam house procedures before the final stage of tanning.
- Soaking: Restoring of the skin’s natural swelling as well as removing of dirt, soluble proteins and preservatives (salt)
- Liming: Removal of hair and epidermis, release of collagen fiber structure and partial saponification of the natural fat
- Fleshing: Mechanical removal of the connective tissue of the subcutis, fat and flesh residue
- Splitting: Separating of the depilated skin into grain leather and split leather
- Bating/Pickling: Additional releasing of the skin fiber structure (enzymes), acidifying of the depilated skin prior to tanning
The tanning process is the irreversible stabilisation of the putrefactive hide substance by permanently altering the protein structure of the hide. If this process isn’t carried out and the skins left to dry, you end up with rawhide.
Tanning can be done by soaking the skin in various chemicals and minerals. For centuries, tannins from the bark and leaves of trees was used. The tannins bind to the collagen proteins in the hide and coat them, which causes them to become less water-soluble and more resistant to bacterial attack. The process also results in the hide becoming more flexible. Tanning can also be done using chromium sulfate (chrome tanning), which involves several stages but is the most widely used process today since it is seen to be more efficient and more effective. However, if the chemicals used are not disposed of responsibly, then they can have a detrimental effect on the environment. Kanpur in India is one example where the leather industry has had a negative effect on the environment.
After tanning and dyeing, the hides are put through a series of finishing processes which vary depending on the final use and destination of the leather. The most frequent of these processes are: drying, conditioning, staking, milling, coating and optional embossing.
The resulting product can then be turned into all manner of goods. Leather is a highly flexible and durable material making it suitable not only for clothing but also furniture covering, bookbinding, cases and even leather wallpaper.
Different types of leather have different characteristics and so are used in different ways. There is also a reflection in the price of the different types of leather available. Higher prided leather tends to be aniline leather, slightly pigmented Napa leather, calfskin, sheep, and deer leather. Average priced leather includes pigmented Napa leather (smooth) and cowhide (the type worn by most leathermen and used in motorcycle clothing). The lower priced leathers are often corrected (sanded) grain, embossed artificial grain, split leather and pigskin.
Leather is a wonderful material and lasts for years if cared for correctly. Here are my top tips for caring for your leathers:
- Check your leathers first with a drop of water. If the water is absorbed rapidly, with a darkening of the leather, then it is unfinished and you should only polish it with a soft dry cloth.
- If the water stays on the surface, clean your leathers by wiping the surface with a damp cloth. If the soiling is more stubborn then a very dilute soap solution can be used instead. Put the soap solution on a sponge, create foam by squeezing the sponge and carefully remove the dirt with a rotary movement. Don’t press too hard as you may remove colour or top coat.
- Don’t buy expensive leather cleaning solutions. Just use normal tab water and a drop of standard washing up liquid. The “expert solutions” do not have any different ingredients.
- Don’t wash your leathers in the washing machine, as the leather may discolour and gets stiff due to the fibers on the backside sticking together as well as the garment becoming brittle.
- Air-dry your leathers on a flat surface. Leather can shrink and become stiff when dried near heat.
- Condition your leathers after cleaning. There is a vast multitude of conditioning products available on the market, from oils to polishes to creams. Work it into the leather using small circular motions. Rub in hard and vigorously and allow to sink into the leather. That way you nourish your leathers.
- After conditioning, buff your leathers by rubbing hard to bring out the shine.
- After cleaning gloves, use a small amount of an unfragranced, non-colour hand lotion and rubber this in whilst wearing both gloves.
Our sincere thanks to Thorsten Buhl for taking the time to share his knowledge. All text and images courtesy of Thorsten and used with permission. All rights acknowledged.