About Optical Brightening Agents (OBAs)
No paper is pure white
Optical Brightening Agents (OBA's) are used to achieve a "bright white" appearance.
High levels of OBA's make paper stock slightly bluish
This essentially makes paper stock a "5th color" in terms of color management.
Bright white papers with higher OBA levels are increasing in popularity
Print designers are demanding these bright, bluish white stocks.
UV Levels in some lighting conditions can make high OBA papers fluoresce
GRACoL 2006 (no OBA) & 2013 (some OBA) proof papers will not show this fluorescence
Left to Right - illustration of increasingly higher OBA and UV levels:

HIGHER OBA PROOFING PAPERS WILL HELP YOU PREDICT AND MANAGE THESE EFFECTS
Relative OBA levels can be measured in L*a*b* using an M1 spectro
The higher the b* value - the higher the OBA's
Here are the b* values for GRACoL papers (including ours)
GRACoL 2006 = b*-2
GRACoL 2013 = b*-4
Here are the b* values for our higher OBA papers
High OBA = b*-8
Max OBA = b*-10
Our portfolio offers all four of these grades in two different weights
We are happy to provide 24" sample rolls of these papers