Brighter Brights and Whiter Whites

I was thinking about something the other day, and I thought I'd share it with you.  It seems like there's always a competition between paper companies to see who can make the brightest/whitest sheet.  The conventional method is by adding optical brightening agents (OBAs) or optical whitening agents (OWAs) at the wetend of the machine.  This seems to work fine but you can only brighten or whiten so much before you lose the effectiveness of the OBA or OWA.

So what else can you do?  Well you can innovate and make a better OBA or OWA.  This would require some collaboration with a chemical company and could take years to develop.  So I started thinking about this and here's what I came up with.

Since the OBAs and OWAs are added at the wetend they have a limited dwell time.  I wonder if increasing this dwell time would allow the OBAs and OWAs to achieve greater brightness and greater whiteness.  If nothing else it could improve OBA/OWA efficiency, get more brightness or whiteness with less chemicals.  So now the question is where can you add it?  How far back can you go? 

What about the pulp mill?  Why can't it be added back there?  It's definitely worth a trial right?  I am not a pulp mill guy though so you should talk with your pulp mill manager to gain insight into where some good addition points might be.  Also remember that if you are going from a grade the requires OBAs or OWAs to a grade that doesn't require OBAs or OWAs that it might take a little while to get all the OBAs or OWAs out of the system.  Ideally you would want to try this at a mill that makes OBA/OWA required paper most or all of the time.

So the concept is to base-load the chemicals in the pulp mill and add as necessary in the wetend to reach your target brightness/whiteness.