Change of paper L a b value

[anjanmazumdar]

It has been noticed in cold set web printing of newspapers the 'b' value of the paper changes .
My question is .
What are the reasions of this change ?
Dose the ph and conductivity of the font matters and how ?
Cheers Anjan Mazumdar

 

[Bob Peterson]

The change in the b* value is usually related directly to the amount of optical brightner in the paper from lot to lot. If you hold various lots of the paper under a black light you will see variences between each of them. A spectrophotometer will see even the slightest difference.