I have posted my bw paper example here for what it is worth (apparently nothing to certain listees) for an illustration of color under tungsten not UV light:As usual, I can speak only about my experience with my printer and UV light source, but at first I confirm one of your observations: the black of R2400 is not as UV blocking like other colors. This fact can be added to the "nonsenses" about inferring UV absorption exclusively on the visible color.
It is nonsense, but not to Twentysomethings :) But apparently Loris, myself, and others find yellow in the Ultrachrome inks to be the densest, whatever the reason if not its color (on 6 different printers for me, but all Epson) but that is not a quantative fact, because it does not related necessarily to dye based printers or HP printers...but it seems I should be careful to "couple" its UV blocking nature to its color opposite the UV spectrum as I think you are saying. I will stand corrected.I have under my eyes the color calibration for kallitype, copper print and oilprint. The first two have the whites printed in the green/green-yellow region, say from H=127° (S and B=100) to H=87°. The third has the whites printed in the yellow region, from H=73° to 52°.
So, iron and dichromate processes (with my printer, etc...) are absorbing in different region. Nothing new...
One source of differences among observations might be the shape of the absorption region of the inks, that of the sensitive compound (iron, dichromate, silver...), and that of the UV emitting source. All are more or less bell-shaped so that this mix gives back a peak with its maximum in a different region of the spectrum. As I have previously said, this is only a probable description which should be confirmed by instrumental measurements.
4. Alberto, did you at all get affected by the earthquake? It has been on the news lots here and I offer condolences.Thank you, Chrstina. I live in Venice (and work in Milan) so I have not been affected at all. The damaged region is up to about 50 km from the epicentre, close to l'Aquila. There are at present 293 dead, about 1500 injuried and about 38,000 evacuees, with the need of 5,000 temporary wood houses in the next three months.
It seems that suddendly we are remembering that most part of Italy is sensitive to earthquakes:
though here and there the anti-seismic building laws have been not applied by some builders in the last decades, and we cannot hope that the ancient buldings (many of them a thousand of years old, or more) can be resistant for ever.