The Company You Keep star portrays one of three women left to fend for themselves at the end of the American Civil War after their remote farm comes under attack from two rogue soldiers.

In one scene, Marling's character is grazed by a bullet, but the rubber prosthetic filmmakers used to create the fake injury wasn't strong enough to protect the actress from the substance they used to clean the wound on camera.

She says, "There's this scene where there's this bullet graze and they had this prosthetic wound on me... and they were gonna cauterise it shut in the scene and they poured the chemical in and I was getting ready for my performance.

"I'm in it and I'm doing this performance and I really start weeping and I'm feeling all this pain and I turn around and look, and the chemical had ate (sic) through the prosthetic wound and started to eat through my skin.

"By the time they got a medic, it was a third degree massive, weeping (burn)."

The injury left a nasty scar around Marling's right arm, but the 32 year old has since undergone laser treatment to make the mark less visible.

She explains, "The power of lasers! Laser surgery just really cleaned that up."