Macintosh 128k with mods by Julian Systems

[MIST]

Some of these screen overlays were meant to protect the users skin. The CRTs front would slightly charge up by the electron beam and dust touching the screen would pick up the same charge and then be pushed away. Some people claimed that this slight but permanent stream of dust particles would have a negative effect on your face's skin ... or stick to your makeup or whatever ...

 

[adespoton]

Some of these screen overlays were meant to protect the users skin. The CRTs front would slightly charge up by the electron beam and dust touching the screen would pick up the same charge and then be pushed away. Some people claimed that this slight but permanent stream of dust particles would have a negative effect on your face's skin ... or stick to your makeup or whatever ...

Part of the idea was that CRTs essentially have an electron gun fired at a phosphor screen, but that a) not all the electrons were going to hit the screen (some would go through and hit the face of the person in front of it) and b) those that did hit could excite the screen, glass, dust, etc. in a way that emitted more harmful radiation.

For the most part, this wasn't actually an issue for CRTs used in monitors (more of an issue in big TVs), but that didn't stop people from selling "filters" that were "guaranteed" to block all harmful radiation.