|Leonard R. Ingersoll optics|
- Leonard R. Ingersoll figured,
- since glossiness of a surface
- does not correlate well
- with its mechanical smoothness,
- an optical method to measure gloss was best.
- The Ingersoll Glarimeter
- compares specularly reflected light
- where the light-source
- is at a sufficiently low angle of incidence
- to cause the light at the angle of reflection
- to be plane polarized,
- with diffusely reflected light,
- which is reflected in all directions.
- The view through the Glarimeter eyepiece
- shows a divided field of view. Diffusely reflected light
- is shown through a smoked glass to the top,
- and specularly reflected light through a Nicol prism
- to the bottom. The operator turns the viewport
- until the line between the two parts disappears.
- The degree of rotation correlates with the glossiness.
Specular reflection is polarized
- Glossiness is an optical not a mechanical property of surfaces.
- Color diminishes the amount of diffusely reflected light
- but not the amount of specularly reflected light.
- In specular reflection, light is polarized.
- A paper with an ideal matte surface, reflecting light only diffusely,
- combined with a dead-black ink, is most readable.
- Calendering paper
- puts it through rollers
- to improve its smoothness.
- Wandering dervishes
- refuse to be calendered,
- although we call them calenders.