There are standards describing gloss levels. One of the good things about standards is that there are so many of them.

The gloss of any sample will appear to change based on the viewing conditions.
There are at least five widely used gloss measuring angles kicking around these days; 20, 45, 60, 75, and 85 degrees.
Each angle sometimes requires using a different instrument.
The most commonly used angles of 20, 60, and 85 degrees are available in a Swiss-Army-Knife type of instrument that costs less than buying three separate units.
We happen to sell a very good unit available in every configuration;
https://betascreen.net/products/qip-gloss-meters?variant=1267498684
Materials of low gloss such as paper need to be measured with a low angle device. This is emulates the manual method of holding a sample in one hand, bending it to form a convex shape, and then holding it up to your eye pointing it towards a light source to catch the grazing reflection. Since the "low angle of incidence" is a high number when measured from the perpendicular to the sample surface, you would use a 75 degree instrument as shown below.
Shamelessly copied from Wikipedia;
https://en.wikipedia.org/wiki/Glossmeter [h=2]Standards[/h] [TABLE="class: wikitable"]
Comparison of standards for gloss measurement [TR]
[TD]
Standard[/TD]
[TD]
20°[/TD]
[TD]
60°[/TD]
[TD]
85°[/TD]
[TD]
45°[/TD]
[TD]
75°[/TD]
[/TR]
[TR]
[TD] [/TD]
[TD]High Gloss[/TD]
[TD]Medium Gloss[/TD]
[TD]Low Gloss[/TD]
[TD]Medium Gloss[/TD]
[TD]Low Gloss[/TD]
[/TR]
[TR]
[TD] [/TD]
[TD="colspan: 3"]Coatings, plastics and related materials[/TD]
[TD]Ceramics[/TD]
[TD]Paper[/TD]
[/TR]
[TR]
[TD]ASTM
C346[/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[TD]X[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]ASTM
D523[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]ASTM
C584[/TD]
[TD] [/TD]
[TD]X[/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]ASTM
D2457[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[TD]X[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]BS3900 D5[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]DIN
67530[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]DIN EN
ISO 2813[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]EN
ISO 7668[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]JI Z 8741[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[TD]X[/TD]
[/TR]
[TR]
[TD]
TAPPI T480[/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[TD] [/TD]
[TD]X[/TD]
[/TR]
[/TABLE]
If you are able to obtain a numerical Gloss Value from a paper or ink supplier, make sure that they specify the measuring angle under which the sample was tested.
You cannot simply apply a correction factor to one angle value to mimic another.
Our industry has a fairly easy job evaluating gloss of paper. Things get really scary when things like molded plastics, auto finishes, metal surfaces need to be evaluated for Haze, Distinctness of Image, Orange Peel, in addition to simple gloss. A goniometer might be your friend, not an STD.
I'll be at the FTA INFO*FLEX in Phoenix next week. Please stop by if you're in town for that or any better reason.
Larry