Gloss
Gloss turns up in 2 fields: powder coating, paper optics. Here is what it means to the people in each one.
Gloss in powder coating
How mirror-like a finish is, read with a gloss meter at a fixed angle, usually 60 degrees.
A gloss meter shines light at the surface and measures how much reflects back at the matching angle, reported in gloss units. At 60 degrees, flat finishes read in single digits, satins somewhere in the 20s to 50s and high gloss 85 and up; very glossy finishes are also read at 20 degrees. Gloss shifts with cure, film build, oven type and contamination, so it is checked against a standard on every lot.
"Gloss is coming in at 72 and the spec is 85 plus, check if the oven's running hot."
Gloss in paper optics
The mirror-like shine of a paper or print surface, measured as specular reflectance at a defined angle.
A glossmeter shines a beam at the surface and measures how much light leaves at the mirror angle, relative to a polished black glass reference. Smooth, closed surfaces from coating and calendering raise it, while roughness, open pores and matte pigments lower it. Paper uses 75 degrees for most coated and uncoated grades and 20 degrees for very high-gloss surfaces.
"Gloss came down four units on the drive side, check the supercalender nip load before we ship it."