National Dental Assisting Examining Board (NDAEB) Practice Exam

When mixing a gypsum product, how does water temperature affect the setting time?

1. Hotter water slows down the set

2. Warmer water speeds up the set

3. Colder water speeds up the set

4. Water temperature has no effect on the set

The correct answer is: Warmer water speeds up the set

Using warmer water when mixing a gypsum product affects the setting time by accelerating the chemical reaction that occurs during the setting process. Gypsum products, such as plaster and stone, undergo an exothermic reaction when mixed with water, which means they release heat as they set. The temperature of the water used influences this reaction: warmer water provides more energy to the system, thus facilitating a faster reaction rate. Consequently, the setting time is reduced, allowing the material to harden more quickly. In contrast, colder water would slow down the reaction, leading to a longer setting time. Water temperature does indeed have a significant impact on how quickly gypsum can set, making it crucial to consider when preparing these materials for dental modeling or impressions. This is why the use of warmer water effectively speeds up the setting process when working with gypsum products.