These are the four words that define a material’s properties:
Hardness-Represents the amount of force required to damage an object of the given material, as well as the potential of the object to deal such damage. The damage is modified by a ratio of striking and struck hardness and must exceed the hardness of each object to deal any damage according to the equation:
Damage = (Striking Hardness)/(Struck Hardness)*Damage-Struck Hardness
Durability-The amount of damage required to destroy an object completely (reducing it to dust) is given by the durability value, which is like health for an object. Total Durability is dependent on volume and the Durability is expressed in points per cubic inch. An object that has taken damage equal to half its durability is considered unusable, but well-placed blows can cut through an object in a single shot.
Flammability-A measure of how easily a material burns. Fire damage to an object is multiplied by the flammability of the object and is taken on a second by second basis over its surface. Normal fire has a fire damage of 1. Paper, having a flammability of 1, takes twice as much damage from fire as a person.
Opacity-Defines the fraction of light/vision that is lost per 1/16th of an inch when passing through the material. Glass has an opacity of .1, so roughly 1/5 of light passes through an inch of medieval glass.