Leather quality control

In order to verify the good quality of the process carried out on the hides, it is possible to make a series of laboratory tests which can allow us either to have the most objective possible judgement on the hides or to confront different samples, different articles, different tanneries with standardised checking methods and with reference values which are the same for everyone. Here we will only look at the tests commonly used for upholstery.

Rubbing resistance - reference rules: ISO 11640.

A little square of felt measuring 1 sq.cm. on which a weight of 1 kg. has been put, is cyclically rubbed on the hide sample and it is calculated after how many cycles there is a loss in colour of the hide and a transfer of the colour on the felt. The colour alteration is measured on the grey scale. This test can be made with dry felt (dry rubbing), with the felt moistened with water (wet rubbing), with the felt moistened with a salty solution (artificial sweat rubbing).

Fixation of the finish - reference rules: ISO 11644.

This test is also called "adhesion of the protecting film". The test is made by fixing the hide sample on a small metal block and verifying which is the traction strength necessary in order to tear the finishing below.

Bending test - reference rules: ISO 5402.

The sample hide, after being fixed by the pliers of a proper machine, is cyclically bent until the chapping of the finishing starts to be evident.

Light fastness - reference rules:  ISO 105/B02.

All colours tend to alter themselves when directly displayed in sun light. As the durability to the light changes according to the chemical nature of the colouring agent, according to the colours and according to the kind of finishing, it is important to verify such durability comparing it with an univocal and precise control reference. In international rules the kind of lamp to be used to simulate an accelerated sun display is specified and also what has to be the different blue colouring used in the achievement of the reference scale which is put inside the equipment together with the sample hide to be tested, in respect of which the discoloration is evaluated (blue scale).

Ageing by heat - reference rules: ISO 17228

It is a test used to verify, thanks to the comparison with the grey scale, the level of the alteration of the colour as a consequence of the artificial ageing caused by a long exposure on a standard heat source. It is also useful in order to verify the behaviour of the hides when used in tropical climate.

Moreover there are other tests, usually less requested by the sofa manufacturer, which we think are all the same interesting:

Tear resistance - reference rules: ISO 3376.

A standard leather strip is put through traction and the breaking load and the extension to the breaking point are measured.

Burst resistance - reference rules: ISO 3379.

A circular leather sample is fixed on top of a cylinder into which air is pumped under pressure. Then we obtain: level of chapping, stretching of the chapping, level of the burst, stretching of the burst. These last two tests are useful to verify the effects of the sagging of the seats after intensive use and also to test the resistance to violent use: is it true that sofas are not made to jump on, but those who have children know very well the difference between theory and practice...

Fire resistance - reference rules: various.

These are tests which are used to verify the fire resistance and the auto-extinguishing capacity of the hides allocated in public areas or for the covering of car and aircraft seats. Each country and each type of use implies different rules.

Finally, there is a further control which we cannot call a "laboratory test" but which we feel should be included in a serious and complete quality control. This is the colour control upon sample reference.

Considering that the intensity and the spectrum of emission of sun light are different according to latitude, to the period of the year, to the hour of the day, and to cloudiness, we use a standard lamp, whose characteristics are described by the rules BS950, part 1, with a temperature of emission of 6500° K, which is replaced every 1000 hours, in order to be sure that the temperature of the filament lamp, and therefore the spectrum of emission, are the most constant possible. Such a lamp, identified by the name D 65 (artificial daylight), has the undoubted benefit to be, like all standardised tests, the same for everyone all over the world for all days of the year.