Sorry Tim, I do not understand what you mean by OBAs.

I live with what I must live with. The theoretical perfection is not there with base density. I have tried highly dilute laundry bleach but there never seems to be a dilution where I can get what I want. Either the bleach removes all or imparts a reddish hue throughout. The metabisulfite and sulferic acid sounds like it just might be the 'color' Farmers reducer. If so, Athiril just might be the next sage. How do I get sulferic acid:hardware store, grocery store, or must I formally apply to the photo chemical folks? - David Lyga