Zanussi ZGF 640 IT Instruction Booklet page 10

Carefully supervise cooking with fat or oil, since these types of
foodstuff can result in a fire, if over-heated.
The stainless steel can become
tarnished if excessively heated.
Therefore prolonged cooking with
potstones, earthenware pans or
cast-iron plates is inadvisable. Also,
do not use aluminium foil to protect
the top during use.
Make sure pots do not protrude
over the edges of the cooktop and
that they are centrally positioned on
the rings in order to obtain lower gas
consumption.
Do not place unstable or deformed pots on the rings: they
could tip over or spill their contents, causing accidents.
Pots must not enter the control zone.
10