What is the best method for ensuring air circulation when applying mastic to mirrors?

Spot-applying mastic is the best method for ensuring air circulation when applying mastic to mirrors because it allows for spaces between the adhesive points where air can flow. This prevents the underlying surface from trapping moisture or air, which can compromise the adhesion and integrity of the mastic bond. When mastic is applied in spots, it creates a pattern that supports the mirror while still allowing air circulation around it, which is particularly important for avoiding moisture buildup that could lead to issues like mold or mirror delamination.

In contrast, applying mastic to the entire back of the mirror creates a continuous seal that can trap air and moisture, preventing adequate ventilation. Using a thick layer of mastic could also reduce the effectiveness of air circulation and lead to uneven drying or curing of the adhesive. Avoiding air circulation entirely would directly contradict the principle of maintaining a healthy adhesive environment.