First-surface mirror

[1] Historically, the bronze mirror, an FSM type, was standard from ancient times until relatively recent centuries.

These were simply highly polished pieces of bronze or other metals, usually small and round, and designed for a person to see their face.

Reflecting telescopes, rear-projection televisions, periscopes, non-reversing mirrors, high-quality kaleidoscopes, and the animation process.

In cases where the mirror is subjected to extreme cold (as low as 33 K as in the James Webb Space Telescope), a polished pure beryllium mirror is used without a first-surface coating in order to eliminate deformations caused by differing coefficients of thermal expansion.

[2] The "silvering" on a front-surface mirror is usually aluminium for visible light and gold for infrared radiation.

Example of a second-surface mirror ( left ) and a first-surface mirror ( right ). In both pictures, the pen is touching the surface of the mirror. "Ghosting" (a faint reflection from the first layer) is visible in the left image (more obvious when this file is displayed at full-size).
Technicians assemble 6 of the 18 first-surface mirrors used in the James Webb Space Telescope .