Whiter & Brighter
Recently, paper mills have busied themselves improving brightness, opacity and whiteness for coated and uncoated papers. To better compete with foreign papers entering the American/Canadian market, along with improved technology and whiteners, these changes now are necessary and affordable.
Some use whiteness and brightness interchangeably, but they aren't the same if you ask the experts. Whiteness, or CIE Whiteness, is the favored measurement in most countries, but brightness is the favored in North America.
But what is the difference between white and bright? Ironically, something that puts you in mind of the absence of color has everything to do with color. Begin with definitions:
Whiteness: a single number index measuring the amount of light reflected from the surface of a paper using total color spectrum across the sheet.
Brightness: a single number index measuring the amount of light reflected from the surface of a paper using just the blue end of the visible spectrum.
To change the brightness or whiteness of a paper, Fluorescent Whitening Agents (FWAs) are added to the pulp during papermaking. Some mills are developing new methods that are said to create whiter papers. With markets expanding globally, some North American mills are moving to measuring in CIE Whiteness as the primary measure for paper instead of brightness.
Brightness measurements also differ according to the standards used. Two standard sets, the TAPPI (Technical Association of the Pulp and Paper Industry) and the ISO (International Organization for Standardization) are used and they don't agree on the measurement of reflectance within the blue spectrum and cannot be used interchangeably. The TAPPI scale, also referred to as the GE brightness, is used in North America, while ISO is used in most other countries.
The changes made by mills are changing the ratings associated with paper classifications. If you are using a grade finder or paper specification guide to select paper, make sure you are using the latest version available.
