Procedures of vegetables tanning ?

1. Preparing the vegetable tanning solution: The first step in vegetable tanning is preparing the tanning solution. This is typically done by soaking vegetable tannins, such as oak bark or chestnut bark, in water to create a tanning liquor.

2. Soaking the hides: The hides or skins to be tanned are soaked in water to remove any dirt or impurities. They are then soaked in the tanning solution for an extended period of time, typically several weeks to several months, depending on the thickness of the hide and the desired level of tanning.

3. Agitating the hides: During the soaking and tanning process, the hides are agitated regularly to ensure that the tanning solution penetrates evenly throughout the hide.

4. Neutralizing the tanning solution: Once the hides have been tanned to the desired level, they are removed from the tanning solution and neutralized to stop the tanning process. This is typically done by soaking the hides in a solution of bicarbonate of soda or other neutralizing agents.

5. Drying and finishing: After the tanning process is complete, the hides are dried and finished to achieve the desired texture, color, and appearance. This may involve stretching, buffing, dyeing, and other finishing processes.

6. Conditioning: Finally, the tanned hides are conditioned to ensure they remain soft, supple, and durable. This may involve applying oils, waxes, or other conditioning agents to the hides.

Overall, vegetable tanning is a time-consuming process that requires skill and expertise to achieve high-quality results. It is a more environmentally friendly alternative to chrome tanning, as it uses natural tannins derived from plants rather than synthetic chemicals.

Vegetable Tanning Procedures

Materials:

- Vegetable tanning liquor (e.g., quebracho, chestnut, mimosa)
- Leather hides or skins
- Water
- Basic chemicals (e.g., sodium carbonate, sodium bicarbonate)
- Tanning drums or pits
- Paddle or beam for stirring

Steps:

1. Hide Preparation:

- Remove hair and flesh from the hides using a fleshing machine or manually.
- Delime the hides to remove excess lime and proteins.
- Soak the hides in clean water to rehydrate them.

2. Tanning Liquor Preparation:

- Prepare the vegetable tanning liquor by dissolving it in water.
- Adjust the pH and temperature of the liquor as per the manufacturer's recommendations.

3. Tanning Process:

- Pit Tanning:
- Place the hides in a pit filled with tanning liquor.
- Stir or paddle the hides regularly to ensure even absorption.
- The tanning process can take several weeks to months.
- Drum Tanning:
- Load the hides into a tumbling drum.
- Add the tanning liquor and rotate the drum continuously.
- Control the temperature and pH of the liquor throughout the process.

4. Tanning Cycle:

- The tanning cycle involves alternating between periods of tumbling and resting.
- Rest periods allow the tanning agents to penetrate deeper into the leather.
- The duration and intensity of the tanning cycle vary depending on the desired leather characteristics.

5. Exhaustion:

- Monitor the strength of the tanning liquor using a titration test.
- Expose the leather to weak tanning liquor (referred to as exhaustion) to remove excess tannins.

6. Neutralization and Washing:

- Neutralize the tanned leather using sodium carbonate or bicarbonate.
- Wash the leather thoroughly with clean water to remove any residual chemicals.

7. Oiling and Drying:

- Apply oils or greases to the tanned leather to soften it.
- Hang the leather to dry in a warm, well-ventilated area.

8. Finishing:

- After drying, the leather can undergo additional processes such as shaving, buffing, or coloring to enhance its appearance and properties.