The easiest and most popular test to differentiate between the two mirrors is the fingernail test:
Place your fingernail against the mirror’s surface.
Look at the gap between your fingernail and its reflection.
If there’s a gap between your nail and the reflection, it’s a real mirror.
If your fingernail touches or almost touches its reflection (no gap), it’s likely a two-way mirror.
Why? Because in a real mirror, the reflective coating is behind the glass, creating a slight gap. In a two-way mirror, the reflective coating is on the surface, so your fingernail and its reflection appear to meet.
Other Tips to Spot a Two-Way Mirror
Check the lighting: Two-way mirrors usually require one side to be brightly lit and the other dark for the see-through effect to work. If the fitting room is brightly lit but the adjacent room is dark, be cautious.
Tap on the mirror: Real mirrors sound solid and dense, while two-way mirrors might sound hollow because they often have a room or space behind them.
Look behind the mirror: If possible, check if there’s any space or room behind the mirror.
