This is an excellent variety of Prussian Blue and we appreciate Golden's dedication to testing. We will update this as more information from Golden becomes available. As a general note on Prussian Blue, we advise doing one's own lightfastness tests in different white paints to see how this pigment may behave. Some preliminary research may indicate that the lightfastness of PB27 may be affected by the use of various mixing whites. One resource on this topic is a video from Rublev/Natural Pigments which shows their tests from their own variety of Prussian Blue (PB27) in various mixing whites. In this case the combination with white created different lightfastness ratings: https://www.youtube.com/live/xFn74zdaDHc?feature=share&t=1286.