The first step was to shave Cotillard's natural hairline back by nearly two inches, giving her Piaf's high and elegant forehead. This area had to be trimmed every day of shooting so Cotillard's own naturally dark hair wouldn't show.
Then Archibald designed roughly eight different wigs for Cotillard, each one mimicking a style actually worn by Piaf at various points in time from the curled-brim 'dos she loved during her 1940s heyday to the tired and tousled hair she wore on her deathbed.
To re-create the ailing Piaf's frazzled, poorly dyed orange locks, Archibald referenced a large sample of Piaf's own hair, which had been cut from the singer's head directly after her death and is now kept at a private museum in Paris.
Archibald dyed her wig for that period a slightly brighter shade (allowing for the fading that had no doubt occurred over the years), and then alternately steamed and baked the hair until it became coarse and damaged enough to appear authentic. "That was what the director wanted -- to make it feel real, not overly stylized or glam," she says.
After the film came out, Archibald received the highest possible compliment on her work from none other than Piaf's former secretary (featured in the movie), who told Archibald, "You got Edith's hair just right!"
"She knew Piaf's hair very well because she used to have to put rollers in it herself," says Archibald, who shares the nomination with makeup artist Didier Lavergne.