Labels:bulletin board | crt screen | dialog box | hakham | monitor | window | windowpane | workwear OCR: Understanding the UL Fire Resistance Directories Calcination Rehydration Rocks are grounded into small pieces then they are heated up to approximately 350F This were chemical reaction called calcination takes place. Gypsum composed of molecules of calcium sulphate and water locked into arigid crystalline structure When psum heated, about 75% of the water driven off steam. The resulting white powder called stucco. When water added to the stucco crystals reform and the sypsum returns to its original hardness. This process called rehydration. Prev Next 350o rigid stucce
