Papermakers sort stilbene brighteners by sulfonate groups: di types have the most affinity for fiber and suit wet-end addition, hexa types are the most soluble and suit coatings and size press, and tetra types sit in between and cover both wet end and size press. Switching type changes dosage curves, carrier demand and greening point, so the shorthand comes up in every brightener trial.
We switched from tetra to hexa in the size press and whiteness went up without the green.
Also heard as
- tetra OBA
- tetrasulfo
Related terms
OBA
Optical brightening agent: a dye that absorbs UV light and re-emits it as blue, making paper look whiter.
Carrier
Water-soluble polymer such as PVOH that boosts optical brightener efficiency in coatings and size-press starch.
Greening
The greenish cast a sheet takes on when optical brightener is dosed past its effective range.