*3.10. Black Ink*

The black ink used for writing all through the manuscript was composed of iron-gall ink, as revealed by the characteristic FORS spectrum with the reflectance level raising in the NIR [31]. The metal composition of ink is homogeneous in all the pages, being rich in iron and copper; at f. 9r a different ink, richer in copper and zinc, was highlighted (XRF spectra in Figure 10a), giving material evidence to the hypothesis of a later insertion for this folio, as suggested by the different style in the writing (Figure 10b,c).

**Figure 10.** (**a**) XRF spectra of the black inks at f. 9r (red line) and at f. 42r. (blue line). (**b**) Black ink at f. 9r (later addition). (**c**) Black ink at f. 3r (original).
