Which type of reversible hydrocolloid material is the most viscous?

The most viscous type of reversible hydrocolloid material is the tray material. This selection is correct because tray materials are designed to be thicker and more viscous to better retain shape and provide support when filling an impression tray. They are formulated to maintain integrity and flow characteristics during the setting process, ensuring that they capture detailed impressions while minimizing distortion.

In contrast, working materials, although designed for detailed impressions, have a lower viscosity to allow for easier handling and application. Injector materials are specifically formulated to be less viscous, facilitating smooth delivery into irretrievable areas. Solid materials indicate a hardened state and would not possess characteristics associated with viscosity, as they are not in a flowable state suitable for impression-taking. Thus, the tray type is ideally suited for its role, confirming its position as the most viscous among the options.