Plaster of Paris itself can be hazardous because of the thermal reactions that occur as the material sets. When water is added to plaster of Paris powder, the water molecules go from a liquid to a solid state by incorporating into the crystal lattice of the calcium sulfate hemihydrate. This converts kinetic energy into heat. If hot water is applied to plaster of Paris to begin this kinetic process, the heat given off from the resulting crystallization can actually burn the patient's limb. Such was the case in this patient, who sustained a third-degree burn to the back of his calf after his limb was splinted with plaster made with hot water. The combination of the hot water and the heat from the plaster's crystallization resulted in this soft tissue injury, which required several plastic surgery procedures for coverage. When applying a plaster of Paris splint or cast, be sure to keep the water at room temperature or at a temperature that allows you to immerse your ungloved hand without any discomfort.