The invention relates to a pane that has undergone a chemical toughening operation so as to have an alkali-metal-ion concentration gradient from its surface over an exchange depth of at least 100 μm, a surface stress of at least 200 MPa, and a strain point at the core of at least 550° C. The pane can be used especially in the field of domestic cooking, as a pyrolytic oven door, stove, fire guard, flue insert, and more generally for separating two gaseous atmospheres at different temperatures. The pane is particularly resistant to heat shocks.