EN 12326 - Sulphur dioxide test

This test is divided in a test for slates with a calcium-carbonate content < 20% and a test for slates with a calcium-carbonate content > 20%.

Slates with a calcium-carbonate content < 20%

The samples are exposed to a SiO₂-bearing atmosphere with different concentration up to 21 days. The water saturated as well as dried samples are put 100 mm above the acid solution. After 21 days or in case of earlier destruction, the sample are taken and dried.
Afterwards, all phenomena like splitting, crack, softening, flaking off, swelling or alteration of the colour has to be reported.

Slates with a calcium-carbonate content > 20%

This test focuses on the softening of a slate. The slate is exposed to a humid and SiO₂-bearing atmosphere. The degree of softening is determined by scratching the surface under a defined load before and after the test of resistance as well as the depth of the scratches.

For each sample the softening zone has to be calculated in the following way:

es = (e₃-e₄)-(e₁-e₂)

whereas e1 to e 4 represent the single thickness measurements in mm.

If slates with a carbonate content of 20 % or above correspond to the coding S 3, then they have to have a minimum single thickness of 8 mm or a thickness according to the following formula:

minimum single thickness =
basic single tickness + 0,5 + [7 x (thickness of the softening zone²)]

* Resistance to sulphuric acid