Brittle is a word that suggests weakness. But this need not be so. What it means is that if you try to bend a brittle material it will snap. Window glass is brittle but it is strong enough for windows if the thickness is sufficient. Concrete is brittle, yet it is used to make buildings. This is because concrete is a fantastic material under pressure, and the weight of a building simply presses the concrete together.

Concrete on its own would be useless for a large bridge because the weight of the bridge might cause the bridge to start to bend, and then the concrete would crack. Engineers know this, so they add bars of steel (which is not brittle) to the concrete to reinforce it.

The strength of a brittle material also depends on its shape. As eggshells show, a brittle material in a kind of ball-shape can be very thin, and yet strong enough to stop it crushing. But when the chick wants to get out, it taps it with its beak. Because the shell is brittle, when it is struck a sharp blow it cracks. That, of course, is also how you break an egg you are about to cook. Now isn't that wonderful!