Blog >> Vegetable Tanning vs Chrome Tanning
Our topic of discussion for this week is vegetable tanning versus Chrome tanning. The tanning method is an essential step for leather manufacturing; it stabilizes the collagen structure in the skin and triggers the leather property to resurface from the skin. The vegetable and chrome tanning are still two widely used processes for leather manufacturing. However, the number remains little for vegetable tanning as people derive greater benefits from chrome tanning.
Vegetable tanning has been a great part of human history. The ancient tanning process can be traced back as far as approximately 6,000 BCE near ancient civilization of Indus Valley. Vegetable tanning, unlike chrome tanning, uses natural resources for its tannin (tanning agent). Plant parts from trees like Chestnut wood (Castanea sativa), Quebracho wood (Schinopsis lorentzii), Tara pods (Caesalpinia spinosa), Catechu (Acacia Catechu), Chinese gallnut (Rhustyphina semialata), Turkish gallnut (Quercus infectoria), Gambier (Uncaria gambir), Mimosa or Wattle bark (Acacia meamsii), Myrobalan (Terminalia chebula), Oak wood (Quercus sp), Sumac (Rhustyphina coriaria) and Valonia Oak (Quercus macrolepis) are used to produce vegetable tannin.
By using natural ingredients, vegetable tanning is considered to be less hostile to the environment and gives more natural look to the finished goods; furthermore, the look will gradually improve with time, giving out a unique patina (a soft sheen that develops on the surface of leather) for its users. Although vegetable tanning creates an everlasting leather, the leather is biodegradable and will disintegrate by itself if proper maintenance is stopped. From the economic perspective, vegetable leather can be sold at higher price than chrome leather; this makes vegetable leather is more valuable than its counterpart.
Despite its positive advantages, vegetable tanning has a lot of drawbacks. It is considered to be inefficient and difficult as the time requires to complete the whole process can reach up to 2 months; moreover, skilled craftsmanship is also inevitable as special knowledge is required in vegetable tanning. Vegetable tanned leather is also susceptible to heat; exposing it to intense heat will cause the leather to shrink and develop cracks on its surface. The appearance of vegetable leather is also greatly affected by the presence of iron as stain marks will appear when they are in contact. In addition, the cost for doing vegetable tanning is very high because of the large amount of water it requires in its process.
Figure 2. Summary Vegetable vs Chrome Tanned Leather
Chrome tanning unlike his counterpart, is more favoured to be used as a tannin; 90% of the world's tannery right now use chromium for their tanning. This element serves as a strong oxidizing agent and can greatly hasten the tanning process. Commonly used in the form of Chromium Sulphate (Cr2(SO4)3) this green powder will penetrate the collagen easily and alter the protein structure inside the skin.
Before the discovery of chrome tanning, vegetable tanning was heavily depended on by tanners to do the tanning process. However, the slow production process was unable to cope with the high demand, majority of tanneries decided to drop the old method and replaced it with the new chrome tanning. Chrome tanning has revolutionized the tanning process by greatly reducing the processing time. With the help of Chromium tanning, tanners now can finish the entire production in just within one day. Another great benefit from chrome tanning is its simplicity, meaning that now everyone can become a tanner with the help of Chromium sulphate. Based on economic perspective, chrome tanning is more economical than vegetable tanning since the costs needed to do chrome tanning is less than vegetable tanning. The leather produced from chrome tanning is also softer and thinner and can be dyed into various colours.
The downside for chrome tanned leather can be felt by our environment. Toxic chemicals such as Chromium Sulfate, might increase the COD level in lakes or rivers in the form of Chromium (VI); Furthermore, Chromium (VI) may cause respiratory disease such as lung cancer when it is inhaled; when it is ingested it may cause diseases such as gastrointestinal disorder and hemorrhagic diathesis. Moreover chrome tanning uses various chemicals that might cause a detrimental effect if its' released to the environment. Moreover, The appearance of chrome tanned leather is less natural compared to vegetable tanned leather and it is not biodegradable.
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