Our Whiteness Scale has been developed to help us describe as accurately as possible the whiteness of the various papers that we stock. Our scale is based on the manufacturer’s paper specifications and a number of technical and ‘real world’ tests. We use a spectrocolormeter to analyse the paper colour and consider the results alongside the manufacturers stated technical specifications in terms of whiteness (CIE measurement) and brightness (TAPPI or ISO 2470-1 measurement).
It is not usual for the CIE measurement to appear relatively inaccurate in ‘real world’ testing, it sometimes just doesn’t look as white as the numbers would suggest! With this in mind we also have three different people rank (‘by eye’) samples of each paper from the most white to least white, with an option to say if the difference between papers is so minimal as to be irrelevant in their opinion. We do this three times- under our standard workshop LED lights, under a 6500k white (slightly blue) light and finally under natural midday daylight.
We give more weight to the natural light, but do consider the other conditions, especially if there is a tie under natural light.
Finally, we compare the ‘real world’ test to the technical data; however we favour the real world test results when compiling the final score.
Our whiteness scale scores should simply be used as a way to compare whiteness between papers without seeing them in person. If the whiteness of the paper is very critical we would highly recommend obtaining a sample pack. The added benefit of this is that you can view the paper under your own specific lighting conditions.
As a fun way to highlight the difficulty with paper whiteness, line up the samples according to our scale and look at them under a warm household light, under a ‘white’ household light or ‘daylight bulb’ if you have one, and under natural midday daylight. You’ll probably notice some interesting subtle differences! Now ask someone else to do the same and see if there are any subtle differences in opinion between 2 people looking at exactly the same paper under the same light- there often is.
A similar issue arises when viewing the colours of a print under different lighting conditions, but that’s a topic for another time!