Lightfastness is extremely important to us. All PanPastel Colors are made using the highest quality artist’s pigments, with minimal binders/fillers.
The lightfastness of a color or pigment indicates how permanent it is, and how unaffected it is by light. PanPastel Colors have been rated according to the American Society for Testing and Materials (ASTM) lightfastness standard†.
When we developed PanPastel we spent almost 5 years perfecting the formulations for each color. We went through hundreds & hundreds of formulations. As an important part of the R&D process we conduct lightfastness testing for every color.
This testing is done independently under museum conditions using the ASTM Lightfastness Standard†. We formulated and re-formulated until we maximized the lightfastness of each color. The resulting lightfastness rating for each color is shown on all our packaging, and color charts.
Colors are measured before and after light exposure according to the CIE-L*a*b* method (i.e.”Commission Internationale de l’Éclairage”). L*a*b* stands for a worldwide standardized method of color measurement, represented by a three-dimensional color system, where L* indicates the position on the grey axis, a* the position on the green/red axis, and b* the position on the yellow/blue axis. The color difference is represented by ∆ E *, calculated from: ∆ E * = √ (∆ L*)² + (∆ a*)² +(∆ b*)². The classification is determined on the basis of this ∆ E*.
If the ∆ E * is less than 4, the colors will show no visible color change under museum conditions for at least 100 years. This group is denoted by Lightfastness Category I. If the ∆ E * is between 4 and 8, the colors will show a slight amount of color change after 50 years. This group is denoted by Lightfastness Category II. Between 8 and 16, is Lightfastness Category III etc.
Our colors relate to the above standards as follows:
**** = I
*** = II
** = III
†As there isn’t an ASTM lightfastness standard for pastels, we used the standard for Colored Pencils, which in our judgement is the closest standard to use.