What toughening actually does
Toughened glass is heated and rapidly cooled in a controlled process. The result is glass several times stronger than ordinary (annealed) glass of the same thickness, and if it does break, it crumbles into small granular pieces rather than long sharp shards. That is why doors, railings, shower screens and table tops should almost always be toughened.
The one rule to remember
Toughened glass cannot be cut, drilled or edged after tempering. Every hole, notch and edge must be finished first, from exact measurements. This is why a good glass shop measures twice and fabricates once, and why changing your mind after tempering means a new panel.
Where annealed glass is still fine
Ordinary float glass remains the right, economical choice for many windows, frames and panes where safety glass is not required and the panel is not a structural or human-impact element. When in doubt, ask, the honest answer is sometimes the cheaper option.
How to tell toughened glass from normal glass
Look in the corner of the panel for a small stamp or etched mark, which most toughened glass carries. Through polarised sunglasses, toughened glass often shows faint dark patches or stripes. And if it ever breaks, toughened glass turns into small blunt cubes, while normal glass breaks into long sharp pieces.
Does toughened glass cost much more?
It costs more than plain float glass of the same thickness, because of the furnace process and the extra care in cutting before tempering. In Pathankot, clear toughened glass runs roughly Rs 45 to 75 per sq ft for 5 mm and Rs 120 to 210 per sq ft for 12 mm, supply only. See the toughened glass price guide for every thickness.
Tuffen, tuffan or tafan glass?
All three are local names for the same thing: toughened glass. If a shop quotes you for tuffen glass, it should be heat toughened safety glass, and it is fair to ask to see the mark.
General guidance only; your application and local building rules decide the final specification.