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The Crucial Interplay of Relative Humidity, Temperature and Moisture in Leather Milling Process

Knowledge of these process variables (relative humidity, temperature and moisture in leather milling) and their correlation determine the final material properties, processing repeatability, prevention of over-drying or over-hydration, process energy efficiency and enhancement of softness and aesthetic goals.

The Crucial Interplay of Relative Humidity, Temperature and Moisture in Leather Milling Process

What is meant by relative humidity, temperature and moisture?

Relative humidity, temperature, and moisture are related but distinct concepts that play crucial roles in various fields, including meteorology, material science, and manufacturing.

Here's a brief explanation of each:

Relative Humidity (RH):

Relative humidity, expressed as a percentage, is the ratio between the amount of water vapour contained in a volume of air and the maximum amount that this volume can contain under the same temperature and pressure conditions. The warmer the air, the more water it can contain in the form of vapour. Conversely, as the air cools, the vapour condenses to form droplets of liquid water because the saturation threshold decreases with temperature.  For example, a relative humidity of 50% means that the air contains half the maximum amount of water it can hold at that temperature.


Temperature is a measure of the degree of hotness or coldness of a substance, typically measured in degrees Celsius (°C) or Fahrenheit (°F). It indicates the average kinetic energy of the particles in a system. In the context of air, temperature influences the air's capacity to hold moisture. Warmer air can hold more water vapor than cooler air.


Humidity is a general term for the amount of water or water vapour in the atmosphere (or, more generally, in a mass of air) contained in a substance. The Moisture content of a particular material, such as leather in our case, refers to the actual water content within the material as a percentage of its weight.

In summary:

  • Relative humidity is a percentage indicating how saturated the air is with moisture relative to its maximum capacity at a given temperature.

  • Temperature is a measure of the thermal energy in a system, affecting the air's capacity to hold moisture.

  • Material moisture is a term that refers to the actual water content within the material as a percentage of its weight.

Understanding and controlling these factors is critical in applications ranging from weather forecasting to industrial processes, where the optimal balance between temperature, relative humidity and moisture content is essential for desired results.


But in the process of leather milling?

In the leather milling process, understanding and controlling the interplay between relative humidity, temperature and moisture is crucial for achieving high-quality leather products.

The Crucial Interplay of Relative Humidity, Temperature, and Moisture in Leather Milling Process

Here's why this concept is important:

Material Properties

Leather is a natural material that is highly sensitive to environmental conditions. Changes in relative humidity and temperature can directly impact the moisture content of the leather, affecting its physical properties such as flexibility, softness, and strength.

Consistency in Processing

Repeatability is crucial in leather production. Controlling the environmental conditions inside the drum guarantees the quality of the milling process of the leather. This allows uniform results between batches, avoiding variations in softness, grain, finish and overall quality.

Preventing Over-Drying or Over-Hydration

Maintaining the right balance of moisture is crucial. Over-drying can lead to stiff and brittle leather, while over-hydration may result in a soggy and weak material. Understanding the correlations allows for precise control, preventing these undesirable outcomes.

Energy Efficiency Efficient control of temperature and humidity not only ensures quality but also contributes to energy efficiency in the milling process. Optimizing these factors reduces the likelihood of rework due to inconsistent results and minimizes waste.i.

Enhancing softness and aesthetic goals

A treatment with the proper control of relative humidity and temperature enhances the softness and aesthetic characteristics preset in previous process steps such as tanning and retanning.

In summary, the relationships between relative humidity, temperature and leather moisture in the tanning process, together with the correct mechanical action in the drum, are critical to maintaining product quality, desired consistency, aesthetic goals and overall production efficiency. Understanding and managing these factors will ensure that the finished leather products meet the desired standards and performance.

This is the reason why Erretre is always dedicated to perfecting the ability to control, manage and understand these parameters in its milling drums.


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