Decoration of Ceran Glass Ceramics

Ceran glass ceramic cooktops are marketed with surface decorations. There are several reasons for this the smooth, shiny surface is rendered even more attractive by suitable decoration. Cooker manufacturers can raise their product profile with attractive decoration of this kind. The practical aspects are perhaps most important of all the decoration clearly marks the position of the cooking zones even when the heating elements are switched off. Decoration makes surface scratches, fingerprints, etc., less noticeable. The thickness 

As mentioned above, Ceran glass ceramic cooktops are decorated with ceramic colours of varying chemical composition (to achieve the extensive colour selection - currently 17 different tints). 

Here e is the expansion Al/l ), a is the tensile stress, —a is the compressive stress, a is the average linear coefficient of thermal expansion, E is the modulus of elasticity, d is the thickness, p is Poisson s ratio, T - Tq is the temperature difference hot/cold. The indices GK indicate glass ceramic, F indicates colour. 

The calculations show that only a very thin colour layer ( 5-7 pm) can be applied so as to adhere, since otherwise the tension threshold is exceeded, leading to chipping off of the composite. This makes it necessary to produce colours that are opaque at such minimum layer thicknesses, which can lead to difficulties in view of pigment particle sizes often exceeding 10 pm. Another difficulty is that the upper cooktop surface of the colours deemed generally suitable for decoration of Ceran cooktops must also withstand other, sometimes extreme, loads. For example, these loads are as follows. 

The colours themselves vary widely and are basically pigmented multi-component systems containing up to 15 components (e.g., AI2O3, Si02, B2O3, Na20, etc.). The precise chemical formulas for individual colours - the result of exhaustive developmental work involving statistical trials and constant optimization - are of course commercial secrets. Table 3.4 lists some of the physical properties of the colours. 

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