Encolhimento Automático TG / GT - Encolhimento Automático

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AUTOMATIC INSTRUMENT FOR THE DETERMINATION OF LEATHER SHRINKAGE (TG/GT)

This test method is designed for the thermal characterization of leather and hides, with particular reference to the determination of the shrinkage temperature. It can be applied to any type of leather or hide, provided that the shrinkage temperature of the material under examination is below 100 °C, this limit being related to the measurement principle and to test safety and repeatability conditions.

The test is based on a slow and controlled heating process applied to a leather specimen, generally prepared in the form of a standardized strip with defined dimensions and fiber orientation. The sample is subjected to a gradual temperature increase in a suitable medium (typically air or a thermostatically controlled liquid), ensuring uniform and reproducible heating.

During heating, the fibrous collagen structure undergoes a thermal transition: upon reaching a characteristic temperature—depending on the type of tanning process (vegetable, chrome, synthetic, or combined) and on the moisture content of the material—the collagen fibers lose stability and exhibit a sudden and irreversible shrinkage. This phenomenon is directly related to the degree of chemical stabilization of collagen induced by the tanning process.

The Giuliani instrument allows the precise detection of the temperature at which shrinkage begins, which represents a fundamental parameter for:

• evaluation of tanning quality and degree;

• comparison between production batches;

• compliance control with technical specifications or standards;

• investigation of material behavior under critical thermal conditions.

Thanks to the slow heating rate, the method minimizes thermal inertia effects and enables accurate and repeatable measurements, making it particularly suitable both for industrial quality control and for research and development applications in the leather sector and in collagen-based materials.

2. TECHNICAL FEATURES

• Acid-resistant painted steel cabinet

• Immersion beaker made of glass with adequate thickness

• High-precision digital shrinkage and release measurement system

• Magnetic stirring system for the test liquid

• Armored heating element with steel support

• Sample lifting control system activated when the set temperature is reached

• Sample immersion control system activated when the set temperature is reached

• Encoder-based system for linear displacement measurement

• Main power switch with safety filter

• Multicolor 7” Easy Touch control panel

FUNCTIONAL PARTS

1. Controlled heating system

This is the functional core of the instrument.
It consists of an electric heating element integrated into a thermal block, designed to ensure a gradual, uniform, and reproducible temperature increase.
The system regulates a constant heating rate, typically a few degrees per minute, which is essential for accurately identifying the onset temperature of shrinkage without introducing localized overheating.

2. Test beaker

This is the container in which the leather sample is housed during the test.
The beaker is made of thermally stable, temperature-resistant materials, ensuring homogeneous heat distribution and minimizing heat losses, so that the sample remains under controlled and stable conditions throughout the test.

3. Sample support and fixing system

The sample, prepared as a leather strip, is anchored using a dedicated hook system.
This device keeps the specimen in a vertical position and under a slight, constant tension, which is necessary to clearly observe the shrinkage phenomenon.

4. Temperature sensor

Temperature measurement is performed by a high-precision sensor positioned in close proximity to the sample.

5. Shrinkage detection system

This subsystem detects the exact moment at which sample shrinkage occurs and uses a zero-friction encoder systemcombined with an electronic reading module.
The system is designed to ensure a clear identification of the onset of shrinkage, which defines the characteristic value of the test.

6. Control and regulation unit

This module governs the overall operation of the instrument and displays setup and test conditions on the Touch panel.
It allows the operator to set test parameters (maximum temperature, A or B mode, maximum shrinkage limits, stirrer activation, test start) and to monitor test progress in real time.
It integrates regulation and safety circuits to maintain stable and repeatable operating conditions.

7. Data display and acquisition system

This includes the Touch display, which allows visualization of the instantaneous temperature and recording of the temperature value corresponding to shrinkage, facilitating result storage and comparison between successive tests.

8. Structure and protective enclosure

The load-bearing structure ensures mechanical stability, thermal insulation, and operational safety.
The external enclosure protects internal components and the operator, while allowing easy access to the test area for sample installation and removal.

Taken together, these functional components operate in an integrated manner to provide a reliable, accurate, and repeatable measurement of leather shrinkage temperature, a key parameter for evaluating the chemical and physical characteristics of leather and tanned hides.