Juan Antonio Bayona wanted The Snow Society to breathe reality, hence he resorted to scientific advice to get around thirty actors to lose weight. The Córdoba doctors and researchers Antonio Escribano father (endocrine) and son (internal medicine) are responsible for 30 actors between 18 and early twenties adapting, chronologically, their body composition and weight to what they experienced of the victims.
The production team also adapted the filming times at the accident site to the climate and meteorological recommendations so that the Valley of Tears looked as similar as possible to what it was like 50 years ago.