Page 124 - QRedition5.0 062021

Quality Requirements Edition 5.0 European Enamel Association

8.7.4 Valuation of pores in enamellings Consideration and Description
The judgement of damage by pores is performed by naked eye. One differentiates:

Definition and cause
Following the definition of DIN 50903: Pores are locally limited interruptions in the enamel- a. open, pulling through pores
ling. Pores are caused by gas reactions during the firing process. Their largest extent is b. open not pulling through pores

mostly found vertically to the enamel surface. Pores are often - especially in light coloured
direct-on enamellings - connected with black specks. In these cases, gas reactions during Open, pulling through pores are interruptions in the enamelling down to the metal
firing convey the adhesive layer, being rich in iron oxides, towards the surface. substrate. They can be made visible by physical (e.g. electrostatic) or chemical methods.

Open, not pulling through pores cease in the enamel layer. They cannot be made visible by

such method, as there is no prerequisite reaction with the metal substrate.

Test report
In the test report to be mentioned:
kind and origin of the test piece
place and date of testing
description of defect, number and size

Direct-on enamelling / pore with black speck (enlargement 200 : 1)

Conventional enamelling with a pore not pulling through (enlargement 200 : 1)

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