indurate

反复加热会使这种玻璃变得更加坚硬。

Repeated heating will ___indurate this type of glass further.

多年的军旅生活往往使人变得冷酷无情。

Years of military life tend to ___indurate a person against all feelings of pity.

长期暴露在恶劣天气中会硬化木材的表面。

Constant exposure to harsh weather can ___indurate the surface of the wood.