I remember the day a glazed panel broke at a villa entrance. A stone thrown up from the driveway hit the bottom corner, the whole pane crazed at once, and it fell onto the threshold as granules the size of a pea. Nobody was cut. The same impact on ordinary glass would have put long blade-like shards on the floor. That difference in failure behaviour is the entire point of tempering.
How it is made
Glass is cut to size, the edges worked, and any holes drilled first. That order matters: after tempering the glass cannot be cut, drilled or ground. The prepared pane is heated to roughly 600-700 °C, then both faces are chilled rapidly with controlled jets of air. Because the surfaces cool faster than the core, the faces end up in compression and the core in tension. That balanced stress is what makes the pane markedly stronger.
How it behaves
- Impact: far stronger than annealed glass of the same thickness.
- Thermal shock: tolerates temperature differences across the pane, which matters on sunlit door panels.
- Failure mode: the entire pane breaks into granules with no sharp edges.
- Edge sensitivity: the stress balance is most critical at the edges, so a point impact there shatters the pane completely.
- No reworking: any processing after tempering destroys the glass.
Tempered versus laminated
Laminated glass bonds two panes with a clear interlayer, so broken fragments stay attached and no opening forms. Tempered glass disintegrates and leaves an opening. Each wins a different argument: tempered where human impact injury is the concern, laminated where intrusion or fall risk is. Entrance doors also use tempered laminated glass combining both. Ask which type a glazed door actually uses; across our glazed villa doors the glass type is chosen by exposure and use.
Where it is used on steel doors
Vision openings in the leaf, side lights, transom panels and wide glazed lobby compositions all use tempered glass. A door is a moving element, so every closing cycle flexes and vibrates the pane, and annealed glass does not survive that repetition. Door glazing also sits at body height where impact risk is highest. Frosted, sandblasted, tinted and patterned variants can all be tempered, so privacy requirements are met within the same product.
Double glazing
Exterior doors use sealed double-glazed units rather than single panes: two panes with a spacer and a sealed perimeter. That reduces heat transfer, prevents condensation on the inner face and cuts sound. A common build uses tempered outer glass with tempered or laminated inner glass depending on use. If the perimeter seal fails, moisture appears between the panes and the whole unit is replaced, so check glazing gaskets and frame drainage annually.
Fire-rated glass is a different product
Tempered glass is not fire-resistant glass. Fire-rated glazing uses different compositions, some with interlayers that expand and turn opaque to block heat. Fitting tempered glass to a fire door voids its rating, because the glass and its framing are part of the tested assembly. Glazed escape doors take glass, bead and seal from the certified system.
Ordering from Türkiye
Because all cutting and drilling happens before tempering, the glazed opening size, thickness, surface type and any hole positions must be final at production stage. Specify the glass area and exposure in your enquiry; on wind-loaded facades thickness and area are assessed together, and we do that calculation for wide glazed compositions in our building entrance door range. Glazed panels ship in separate crates, upright with edge protection, loaded in Istanbul alongside the door leaves.
