Gorgias for dating Indian Mughal manuscripts

Titanum white, rutile or anatase?
Titanium white is a general name to indicate a white pigment that is made of one (or a mixture) of the two forms of
titanium oxide: anatase and rutile. These crystals have the same chemical formula, TiO2, but different relative positioning of the 3 atoms (they are 2 polymorphs of titanium oxide).
The standard Pigments Checker v.5 has the rutile titanium white. Nowadays titanium white is all made from rutile. But
this was not always the case. From about 1920 titanium white was made mostly of anatase because it was easier to produce. From about 1940 a cheap production method for rutile was
established and it replaced anatase since it was more lightfast and had a stronger
hiding power.
The new “modern and contemporary art” pigments checker has the “anatase” titanium white. Figure [1] shows the reflectance spectra of the two types of titanium white, anatase, and rutile acquired on the two pigments checkers, “standard” and “modern & contemporary art”.

The two types of titanium white can be distinguished by their reflectance spectra since the absorption band in the UV has the inflection point at 405 nm for rutile and 380 nm for anatase.
We did test the Gorgias spectrometer on an Indian Mughal manuscript that was supposed to be from the 18th century,
likely 1790, figure [2].

We were interested in evaluating the authenticity of the item and, in particular, its dating. As shown in figure [1] the spectrum of the white paint (point 4) is comparable to the spectrum of anatase. This type of titanium white was also confirmed with the Raman Spectroscopy system ElviRA.

We know that anatase was in use from roughly 1920’-1940’. For a manuscript supposedly made in the 18th century, we
were expecting lead white pigment, definitely not anatase. Furthermore, the identification of anatase indicates that the object was created not much later than the 1940’, otherwise, we should have found more of the rutile titanium white.

A. Cosentino “Application note 4: Gorgias Reflectance Spectra Database for Pigments Checker Modern & Contemporary Art” 2022.