How can one determine the mirrored side of a one-way mirror using a traditional test?

The method of using a pencil point to touch the surface is a traditional and effective way to determine the mirrored side of a one-way mirror. When you touch a one-way mirror, if the surface feels solid and you can physically touch it without any gap, then you are on the side with less reflective coating, where the glass is meant to be observed through.

On the other hand, if you touch the reflective side, the pencil point will not make contact with the glass because of the air gap created by the mirror effect. This phenomenon occurs due to the physical properties of the mirror where an image is produced when light reflects off its surface, preventing direct contact with the pencil.

While color differences, light reflection, or measuring thickness might provide some information, they are not as straightforward or reliable as the pencil point test in determining which side is mirrored.