What solution is used to saturate the sponge when using a holiday detector?

The use of tap water with a wetting agent to saturate the sponge in a holiday detector application is essential for enhancing the detector's sensitivity and effectiveness. The wetting agent reduces the surface tension of the water, allowing better penetration and coverage on the surface being tested. This improved wetting ensures that the electrical current can traverse the surface adequately and detect any discontinuities or holidays in the coating.

When using distilled water, while it is pure, it may not effectively create the necessary adherence to the surface without the inclusion of a wetting agent. Acrylic solutions and alcohol-based solutions serve different purposes in coating applications and would not provide the same functionality needed in the holiday detection process. Thus, the combination of tap water with a wetting agent is the most suitable choice for saturating the sponge in this context.