Potassium Dichromate Uses In Leather Tanning Industries

Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent used in laboratories and for industrial use as an oxidising agent used in tanning leather with a molecular mass of 294.185 g/mol. It has its origins same as the hexavalent chromium compounds. Since it has many properties similar to chromium compounds, it is acutely and chronically harmful to health; it is a crystalline ionic solid with a bright, red-orange colour. The salt is popular in the laboratory because it is non-deliquescent and used in analytical chemistry. It is also considered a more suitable salt than sodium dichromate for industrial use.

How is Leather Made?

How leather is made nowadays hasn’t changed much over the past years. It is one lengthy and technical process that requires utmost care and knowledge. It is supposed to be done with precision, and each step of the process has to be followed correctly to produce high-quality leather with a neat finish. 

Selection of hiding

The process will start with animal hide determining how leather is made and selecting its quality based on animal hide. With a good hide, 80-90% yield can be procured. 

Skin Removal

The preparation of a hide starts with the skin removal of the animal, which can be performed by hand or a fleshing machine. The skin removal by hand requires the process as quickly as possible so that the material doesn’t dry out. You should be left with a white, clean surface at the end of the process. The skin is left with a clean white surface as the process is done.

Preservation & Processing 

• Once the skin is procured, it needs to be preserved. The hide is covered with a generous layer of salt that prevents skin from decomposing. If it’s not preserved, the decomposition process can begin resulting in the hide being useless. Therefore it must be salted, brined, or frozen immediately. 
• The hide is preserved in such a way until it’s ready to be processed. It is soaked in water to remove the dirt particles. The hair left on the hide is removed using a chemical solution of calcium oxide. It is also called a lime bath and is kept for one to two days. It aids in the softening of the hide. 

• This process is left by a hide around 4mm thick and can be spliced into two layers. The procedure helps the industry workers separate and distinguish the skin according to its proper use. The upper part of the leather split produces the highest quality leather products, such as full-grain leather. The upper layer has a much tighter fibre structure that sustains its durability. The bottom layer of the hide is comparatively of a lower quality than the upper layer. Therefore it is used for cheaper leathers. 

Process of tanning leather

• Once the hide has been prepared, the second stage is tanning the leather procured.
• This procedure starts by loading the leather into a tanning drum with a special tanning solution: a mix of vegetable tanning agents or a potassium dichromate mix. 
• Chromium salts help produce more stretchable leather, therefore used for clothing apparel like jackets, pants, etc., and handbags. The vegetable extract-treated leather is used for luggage and furniture. In some industries, both vegetable and chromium salts are combined for tanning. 
• Combining both tanning agents helps produce a better quality leather that is soft and supple. At the end of the first tanning leather procedure, special fats are added, a liquoring process to make the leather stronger and more durable.

Final Touches 

• This procedure is sometimes followed by re-tanning leather to achieve its desired tone. The leather’s moisture is to be dried after the tanning procedure. It can be done by air-drying or vacuum drying the leather.
• A dyeing process can also follow the re-tanning of leather to add colour to the finished leather design.

The last stage is adding the finishing touches. This step is crucial and is followed by an inspection of the product. The tests are performed to determine how leather is made of a product.

Conclusion 

The quality of the animal hide is essential for determining how leather is made. Animals that have been branded have suffered a lot of insect bites, kept near barbed wire fences, etc., would have more damaged hide, and the yield from their hide would be around 60% to avoid blemishes and holes. Once the tanning of leather is done and dried under pressure, many surface finishes of coats, dyes, waxes, and oils can add to it, which helps to add protection, add some trendy touch to it, and other purposes according to demand.