затвердевать означает в английский

set up▼(to gel or harden)
verb
[UK: set ʌp] [US: ˈset ʌp]

solidify [solidified, solidifying, solidifies]▼(intransitive: to become solid; to freeze)
verb
[UK: sə.ˈlɪ.dɪ.faɪ] [US: sə.ˈlɪ.də.ˌfaɪ]