Itaque cum est in expolitionibus conclavium tectis inductum, permanet sine vitiis suo colore; apertis vero, id est peristyliis aut exhedris aut ceteris eiusdem modi locis, quo sol et luna possit splendores et radios inmittere, cum ab his locus tangitur, vitiatur et amissa virtute coloris denigratur.
And so when it is used in the finishing of enclosed apartments, it remains of its own colour without defects; but in open places like peristyles and exedrae and so forth, where the sun and moon can send their brightness and their rays, the part so affected is damaged and becomes black, when the colour loses its strength.
final_alignments\Vitruvius_Architecture_Book_7.json