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Hohenstein measures performance of functional garments

19 Dec '08
8 min read

To assess the surface structure of textile substances in order to gauge their comfort in terms of skin sensibility, a number of different laboratory tests have been developed at the Clothing Physiology Department of the Hohenstein Institutes.

Cling index:
A porous, sintered plate of glass to which water is supplied using a calibrated motorised burette simulates perspiring skin. The textile specimen is fastened to a cylinder and pulled across the plate. The force required to do this supplies what is called the cling index, which is used to evaluate whether the textile will cling uncomfortably to the skin when the wearer is sweating.

Number of contact points and surface index:
A surface scanner, or alternatively, a microscope linked to an image analysis system shows the number of contact points for the textile and surface index. This indicates how much the contact surface the textile material has with the skin and the hairiness of its surface. During decades of research, the scientists at Hohenstein have defined threshold values for the optimum number of contact points and the surface index.

Stiffness:
For determining the stiffness or bending angle of a textile substance a laser measurement is taken on a strip of fabric that has been placed on a thin bar. Based on their years of experience, the scientists at Hohenstein have defined standards for products and areas of use that guarantee optimal wear comfort and rule out mechanical skin irritations caused when stiffness is too great.

Sorption index:
Skin becomes more sensitive to mechanical irritation as moisture increases. As a result, it is advantageous for sensitivity and wear comfort when a textile substance transports perspiration away from the skin as quickly as possible. The sorption index is the speed at which a textile absorbs the drops of water with which it comes into contact. A drop of water is placed on the textile specimen and observed using a video camera. The angle of contact of the drop of water on the textile's surface is continually monitored and recorded, indicating how quickly the material is able to absorb sweat.

One mark for wear comfort:
The results of the tests carried out on the skin model and thermo-regulation models all come together with assessment of skin sensibility to make up one grade known as wear comfort or sleep comfort. This is possible because research results have shown that, for example, in the case of garments worn daily, thermo-physiological characteristics account for about 66% percent and skin sensibility for about 34% of perceived wear comfort.

Evaluation of wear comfort is done according to the German school grading system, where 1 is "very good" and 6 is "unsatisfactory". The comfort marks are used today by numerous manufacturers in the form of the Hohenstein Quality Label. These are attached to the product and allow the consumer to make a simple comparison between different products.

Hohenstein Institutes

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