Leather tanning: Discover the key stages in the manufacture of quality leather

Leather is a noble and durable material, but did you know that its manufacture involves a complex process called tanning? In this article, we explain in detail the steps involved in tanning calf and crocodile skins, to help you better understand how to transform a perishable material into rot-proof, hard-wearing leather. Whether you’re a craftsman, leatherworker or simply passionate about leather, this comprehensive guide will enlighten you on the techniques used by tanneries to produce high-quality leathers.

Stage 1: Raw hide sorting – the basis of quality leather

Before tanning begins, it is crucial to sort the raw hides. This step ensures that each batch of hides shares similar characteristics, which is essential for obtaining a homogeneous result.

• Criterion 1: Physical selection
  Hides are classified into three categories: choice 1, 2 or 3, according to their visual quality and condition.
• Criteria 2: Weight and Size
  Calf skins are grouped by weight (heavy, extra-heavy, extra-heavy large sizes), while crocodile skins are sorted by size for uniform tanning.

This sorting allows us to determine the right tanning agents for each batch, thus ensuring top-quality leather.

Stage 2: The River – Preparing the skins

The river is a crucial phase that lasts about a week. It comprises several sub-stages:

1. Soaking: Rehydration of salted skins to remove salt and prevent bacterial proliferation.

2. Stemming and Fleshing: Cleaning the skins on the blossom and flesh sides.

3. Dehairing: Removal of hairs or scales (for crocodile skins).

4. Pelain: Bathing in a sewing machine to ensure gentle treatment.

5. Confit: Enzymes are used to clean hair follicles.

Stage 3: Tanning – Turning hides into leather

Tanning is the stage that transforms the hide into rot-proof leather. Tanneries du Puy mainly use mineral tanning, a fast and efficient technique that gives leather excellent resistance to heat and tearing.

• Foulon tanning: Hides are placed in rotating vats with tanning agents.

• Curing: Calf hides dry for 24 hours, while crocodile hides require 2 weeks.

• “Wet Blue” condition: Calfskins are kept moist for better assimilation of tanning agents.

Stage 4: Leather Dyeing – Giving Color to Leather

Dyeing is an artistic and technical stage. The leathers are immersed in drums with dyes and oils to obtain the desired hue. After dyeing, the leathers are wrung out and vacuum-dried to adjust their firmness.

Stage 5: Trimming – refining leather suppleness

The corroyage process relaxes leather that is too firm after drying. Using fine rewetting and vibratory beating, the craftsmen adjust the suppleness of the leather to obtain a homogeneous batch.

Step 6: Finishing – The Final Touch

Finishing adapts the leather to its final use. Whether for leather goods, footwear or other applications, this stage includes :

• Pre-finishing: Preparing the leather to absorb substances.

• Base: Application of pigments for color.

• Fixation: Use of hot rollers to fix colors and provide gloss and resistance.

Conclusion: Tanning, an Essential Craft Skill

Tanning is a complex process requiring expertise and precision. Each stage, from sorting the skins to finishing, contributes to the final quality of the leather. Whether you’re looking for calf leather for leather goods or crocodile leather for high-end creations, understanding these steps will help you better appreciate the value of this exceptional material.

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