From What Were Greek Masks Made?

None of the original Greek masks have survived time to be studied, but records indicate that the masks were made from organic materials like stiffened linen, bark, wood or leaves. The masks that exist today are made of terracotta and were not worn by actors. The terracotta versions were put outside the theaters for decorations or were put on temples as offerings to the gods.

The masks served several purposes in the Greek theater. The masks made characters more recognizable, allowed one actor to portray numerous parts and allowed men to portray female characters. Women were not allowed to act or participate in theater in Ancient Greece, so the masks were essential for plays with female roles.

The masks had no substantial profiles when viewed from the side. This was to allow the actors to see through the small eye holes in the mask. This design also lent more impact to the moments when an actor looked straight at the audience. Normally, the Greeks preferred to use profiles in their art, but in theater they switched to full eye contact for death scenes and other significant moments of a production to signify their importance to the play and to the character.