затвердеть означает в английский

congeal [congealed, congealing, congeals]▼(to change from a liquid to solid state)
verb
[UK: kən.ˈdʒiːl] [US: kən.ˈdʒiːl]

harden [hardened, hardening, hardens]▼(become hard)
verb
[UK: ˈhɑːd.n̩] [US: ˈhɑːr.dn̩]

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]