Turning hides to leather is a centuries old industry. The hides of animals are treated with chemicals to amend the structure of the collagen fibres to making it more durable and less susceptible to decomposition. The process often allows for colouring the hide for aesthetic purposes. The hides undergo many processes to become leather but can be broken down into these main principles:
Liming and Hair Removal
The addition of alkalis to remove hair from the hide. Typical chemicals used at this stage include sodium hydroxide and sodium sulphide, calcium hydrogen sulphide, sodium hydrosulphite, dimethyl amine and sodium sulphydrate.
This process is to remove the alkali traces and reduce the pH prior to the tanning processes. This can involve acetic acid, lactic acid or boric acid combined with buffering salts such as ammonium sulphate or ammonium chloride to control the process.
The hides are treated with salt, sulphuric acid or formic acid to reduce the pH of the collagen fibres. This allows better penetration of the tanning agents.
Vegetable tanning has no chemical risk and although more environmentally friendly is a slow process taking a number of days.
Mineral tanning - otherwise knowns as the chroming process is very quick but utilises corrosive chemicals such as chromium sulphates
This industry has a wide range of corrosive and chemical risks throughout processing but also in associated processes such as effluent treatment, sludge treatment and dyeing processes.