The type or thickness of the burn can also be recorded on the diagram.  Many burns are mixed in nature, for example, the outer edges may be partial thickness, while areas of deep partial and full thickness burns may extend toward the center.  The appearance of the burn, along with the presence of blanching, blisters and pain helps to determine the extent of the injury. 

The percentage of burns may change as the tissue injury evolves and more extensive tissue damage becomes evident.  Infection can increase the severity of the burn over the course of the injury.