Understanding Whiteness and Brightness

What is light and how do you see objects? Light is actually made of all colors combined together. You see those colors when you see a rainbow.  Light strikes an object and some of the colors are absorbed by the object while some reflect into your eyes. When you look at the sea, it is blue because the sea is absorbing all colors but blue; the blue is reflecting to your eyes. This is important to understand as you want a measurement device to work in a way similar to your eyes.
    
What is the key to paper’s appearance? In order to keep paper consistent, you need standards and measuring devices. Instruments are created per standards defined by industry associations and are certified and calibrated to insure accuracy. TAPPI has a standard to measure brightness (also know as GE brightness). An international organization, CIE – the International Commission on Illumination, developed a single metric to describe the appearance and appeal of paper called whiteness.  IP has the equipment to measure both (brightness – a GE brightness meter and CIE Whiteness – a spectrophotometer) at all of its facilities.  CIE whiteness is measured on a spectrophotometer which is calibrated with internationally traceable standards.

What is brightness? This is the traditional measured value that appears on most reams of paper in the U.S. You may think it is a measure of how much light bounces back into your eye, but it is not. The GE brightness measures only a portion of reflected light (see the illustration below). It was originally designed to quantify pulp bleaching and for the lack of other instrumentation was adopted to measure paper brightness. Globally, brightness is no longer a primary measure for paper.  It has been replaced by CIE whiteness which is more relevant as it measures paper much like your eye sees.
   
What is whiteness? The absence of other colors in white makes for good contrast with printed color combinations. Cream shaded papers are not favored as they are associated with aging and fading.  People favor papers with a slight shift to the blue shade which they associate with newness, freshness and cleanliness.  International Paper’s introduction of whiteness through its VIP Technologies™ assures the highest benefit under the most economical conditions-- greater value to you and your customers.  For uniformity across all uncoated white paper grades, International Paper has standardized on the globally accepted CIE 145 whiteness.
 
What is more important-- whiteness or brightness? If you want to have more impact-- focus on whiteness.  Whiteness is more important and accurate with regard to the human perception of quality and uniformity of paper than is brightness.  Whiteness is the best descriptor of the appearance of white paper.