occurs when gypsum board (also known as wallboard or sheetrock) is exposed to heat and the water of crystallization in the calcium sulfate layer is lost. As the paper and paint burn off the gypsum board, the board turns gray and begins to disintegrate. As the carbon is burned away, the wall becomes whiter. The difference between colors on the wall may show lines of demarcation that can assist the investigator in interpreting fire flow.
