Revealing the Nature of Black Pigments Used on Ancient Egyptian Papyri from Champollion Collection.

Although numerous papyri from ancient Egypt have been collected and preserved over the centuries, the recipe used to prepare black inks was only reported in manuscripts from the late Greco-Roman period. Black inks were mostly obtained after mixing carbon black with a binder agent and water. In previous studies performed on black inks apposed on papyri from ancient Egypt, additional chemical elements such as lead, iron, or copper were also identified, and the resulting chemical contrast with the papyrus support was used to virtually decrypt highly degraded or rolled papyri. Combining a series of synchrotron-based techniques with Raman spectroscopy and scanning electron microscopy, we investigated 10 papyri fragments from J.-F. Champollion's private collection. For each fragment, the carbon-black pigment found in the ink is identified as flame carbon (lampblack or soot). Using X-ray diffraction computed tomography, we show that the diffraction signal of the carbon-based pigment itself can be isolated. As a result, a contrast with the papyrus support is obtained, even in the absence of a specific chemical element in the ink. This is opening up new opportunities to decipher words written millennia ago, as part of our Cultural Heritage.

Illustrating papyrus in Ancient Egypt.

Illustrated papyruses from Ancient Egypt have survived across millennia, depicting with vivid colors numerous stories and practices from a distant past. We have investigated a series of illustrated papyruses from Champollion's private collection showing scenes from the Book of the Dead, a document essential to prepare for the afterlife. The nature of the different pigments and their distribution are revealed by combining optical microscopy, Raman spectroscopy, and synchrotron X-ray powder diffraction and fluorescence. The standardized three-step process from the New Kingdom period was used, comprising a preparatory drawing made of red hematite, a coloring step using pigments from the Egyptian palette, and a final black contour drawn with a carbon-based ink. Interestingly, specific pigment mixes were deliberately chosen to obtain different shades. In some parts, the final contour significantly differs from the preliminary drawing, revealing the artist's creativity. These results enhance our knowledge of illustrative practices in Ancient Egypt.

Association of indigo with zeolites for improved color stabilization.

The durability of an organic color and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidizing conditions, using Raman and ultraviolet-visible (UV-Vis) spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In the absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high color stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment.

Synthetic hydrocerussite, 2PbCO(3) x Pb(OH)(2), by X-ray powder diffraction.

Synthetic hydrocerussite [trilead dihydroxide dicarbonate, Pb(3)(CO(3))(2)(OH)(2)] can be easily obtained, as a white powder, by the action of carbon dioxide and water on either lead or litharge at pH 4-5. This compound is also found in lead corrosion technological products as a fine-grained phase. Ab initio crystal structure determination was carried out on X-ray powder diffraction data. The heavy-atom method and the Patterson function helped determine the crystallographic model and the atom locations. The Rietveld fitting procedure was used for the final refinement. The atomic arrangement is closely related to the structures of other lead hydroxide carbonates. The hydrocerussite structure can be viewed as a sequence of two types of layers stacked along [001]. Layer A is composed of Pb and CO(3), and layer B is composed of Pb and OH. The stacking sequence is ...BAABAA...