Testers cut several sheets from a reel sample, stack them all facing the same way and read the top sheet with the rest of the stack as its backing. A good pad has the side under test facing up, no folds or fingerprints, and enough layers that one more sheet changes nothing. Readings off a thin pad pick up the instrument backing and wander from test to test.
Heard on the job
Build me a ten-sheet pad, felt side up, and give me brightness and the Lab numbers off it.
Also heard as
- opaque pad
- stack
Related terms
R-infinity
Reflectance factor of a pad so thick that adding more sheets no longer changes the reading.
Brightness pad
Thick, flat test disc formed from pulp slurry so brightness can be read on an opaque surface.
Reel sample
Strip of paper torn across the full width of a finished reel for lab testing before the reel is released.