Industrial Maintenance Technician Practice Test 2025 - Free Maintenance Technician Practice Questions and Study Guide

The best time to apply a second coat of plaster is when the first coat is still tacky because this condition allows for optimal adhesion between the two layers. When the first coat remains slightly damp or tacky, it enables the plaster to bond effectively, creating a stronger and more cohesive surface. This technique is critical as it ensures that the second coat becomes integrated with the first rather than simply sitting on top of it.

Application after the first coat has completely dried would lead to a less effective bond, as the surfaces may not interact as well due to a lack of moisture that aids in bonding. Similarly, waiting for a full 24 hours or applying before the first coat sets could compromise adhesion as well; the first coat may be too dry, leading to delamination, or it may not provide enough structural integrity for the second coat to adhere properly. Therefore, applying the second coat while the first is still tacky is key to achieving the desired durability and finish in plastering work.