Which term describes glass that is stronger than annealed glass but not as strong as tempered glass?

• A. Laminated
• B. Annealed
• C. Heat-Strengthened
• D. Tempered

Answer: (C)

When thinking about glass strength levels, you start with the baseline: annealed glass, which is the standard, unreinforced form. The strongest widely used option is tempered glass, which has full surface compression created during rapid cooling, giving it much higher strength and a characteristic break pattern. Between these two is a middle option produced by heating the glass and then cooling it more gently to induce surface compressive stresses without reaching the intensity of tempering. This intermediate, heat-strengthened glass is stronger than annealed but not as strong as tempered, which is why it’s chosen for applications that need extra strength without the full capabilities (and sometimes higher cost or different break behavior) of tempered glass. Laminated glass adds safety through the interlayer and can improve impact resistance, but its strength classification isn’t about the heat-treating level like heat-strengthened glass is. So the term that fits the description—stronger than annealed but not as strong as tempered—is heat-strengthened glass.