Disclosing Colors and Pigments on Archaeological Objects from the Aga Khan Necropolis (West Aswan Egypt) through On-Site Analytical Methods: Preliminary Results

: The present study is aimed at the characterization of artifacts excavated in the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt), as part of the Mummies Investigations Anthropological & Scientific West Aswan Necropolis (MIASWAN) project. Four cartonnages and some pottery shards were investigated on-site by means of non-destructive and micro-destructive techniques, such as attenuated total reflection/Fourier transform infrared spectroscopy (ATR/FTIR) and visible reflectance spectroscopy Vis-RS). Thanks to the use of these techniques, several pigments employed in the creation of the artifacts were identified. Due to the impossibility of transporting the investigated objects out of Egypt, a first-ever on-site characterization of the artifacts from this important excavation was carried out through scientific methodologies. These extreme conditions made the use of analytical instrumentation very challenging. Nevertheless, several characteristic pigments and hues were successfully identified.


Introduction
A fundamental aspect of the study of artistically and historically significant painted objects is the identification of the compounds employed in their creation.Important information on the artifact can be obtained through the use of appropriate analytical methodologies, such as the painting technique, the availability of natural pigments, the ability of producing pigments from raw materials, and, consequently, evidence on the technological expertise in a particular historical period.
Furthermore, the physical and chemical characterization of materials can allow the detection of previous restoration or conservation work.In some cases, information on the authenticity and/or dating of the artwork can also be obtained.Indeed, research studies conducted in this field were able to identify the array of colors the ancient Egyptians had at their disposal [1][2][3][4][5][6][7][8].
Throughout millennia, the fascination for hues has always pushed mankind to search for different natural pigments to be used as colors or to find alternative ways to produce pigments synthetically.Evidence of the first synthetic pigment in history, Egyptian blue [9][10][11], dates to the Egyptian era.Indeed, thanks to the known technical skills of the Egyptians, it is thought that the pigment began to be produced around 3000 BC.It was the most widespread pigment in Egypt from the first dynasties to the end of the Roman era.
The symbolism of the colors also allows us to understand why Egyptian pictorial art is often associated with funerary art, where the purpose of the rich religious decorations was to make the afterlife more comfortable for the deceased.
Cartonnage is the term used for plastered layers of canvas or reused papyrus, where an extensive use of color has been made [12][13][14].Cartonnage is flexible enough for molding while wet against the irregular surfaces of the body, making it the preferred choice to be used in funerary workshops to produce cases, funerary masks, or panels to cover all or part of the mummified and wrapped body [15].
In the present study, on-site spectroscopic analyses were carried out on some cartonnages excavated in the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt), as part of the Mummies Investigations Anthropological & Scientific West Aswan Necropolis (MIASWAN) Project.The excavations conducted since 2018 revealed an 800-year period covered by the necropolis, ranging from the 6th century BC to the 2nd AD.The analyzed artifacts were four different cartonnages and two pieces of pottery coming from tombs excavated in the necropolis.
To date, six campaigns of the Egyptian-Italian Mission at West Aswan (EIMAWA) mission, two of which in the framework of the MIASWAN project, were conducted by the scientific multi-disciplinary research group coordinated by Prof. Patrizia Piacentini of the University of Milan.The area of the excavation concession is approximately 100,000 square meters, of which, approximately 25,000 were mapped, uncovering the entrances to approximately 300 tombs (Piacentini, Pozzi Battaglia, Abd El-Moneim 2020).
The finds of the latter study come from two of the excavated tombs: AGH026 and AGH032.AGH026 revealed the presence of at least 46 individuals, including 14 complete mummies and commingled skeletonized and partially mummified remains, along with numerous other objects, including fragments of cartonnages of different sizes, such as foot covers, head covers, collars, and small fragments.All these artifacts still show vibrant and bright colors.In the second tomb (AGH032), 20 mummified bodies of adults and children were found wrapped in bandages with fragments of cartonnage still in place.The skeletonized human remains led to the identification of other 32 individuals.However, the study of the human remains of the Aga Khan necropolis attests to the presence of mummies composed of bones of different individuals.Similar findings are also attested in contemporary necropolises [16].This makes it difficult to establish the exact number of deceased people who occupied the tomb, which could be around 45 individuals or less.
With regards to the artifacts in tombs, Egyptian law states that nowadays no item can be transported out of the country.Therefore, only on-site and non-destructive measurements are permitted using preferably portable instrumentation.
For this reason, the aim of the measurement campaign carried out from May to June 2021 was to evaluate the possibility of acquiring data through on-site analyses with instrumentation coming directly from Italy.Therefore, light and easy-to-use portable devices were employed, including a portable attenuated total reflection Fourier transform infrared spectroscopy (ATR/FTIR) instrument and a visible reflectance spectrophotometer, in order to obtain preliminary results on the investigated objects with the idea of conducting further investigations during subsequent campaigns.

Analyzed Samples
Four cartonnages and two pottery shards coming from tombs AGH026 (Figure 1) and AGH032 were analyzed (Table 1).These samples were chosen from finds that were being restored at the same time, encouraging interactions between the work of the restorers and the chemists.

Analyzed Samples
Four cartonnages and two pottery shards coming from tombs AGH026 (Figure 1) and AGH032 were analyzed (Table 1).These samples were chosen from finds that were being restored at the same time, encouraging interactions between the work of the restorers and the chemists.Table 1.List of the analyzed artifacts and the corresponding performed analysis.

Analyzed Samples
Four cartonnages and two pottery shards coming from tombs AGH026 (Figure 1) and AGH032 were analyzed (Table 1).These samples were chosen from finds that were being restored at the same time, encouraging interactions between the work of the restorers and the chemists.

AGH026-B13
Four cartonnages and two pottery shards coming from tombs AGH026 (Figure 1) and AGH032 were analyzed (Table 1).These samples were chosen from finds that were being restored at the same time, encouraging interactions between the work of the restorers and the chemists.

Visible Reflectance Spectroscopy
The first artifact (AGH026-B14) was discovered in the 2019 excavation campaign.It is a cartonnage helmet, approximately 22 cm in diameter, from which the mask was removed by looters in ancient times.It is found in the south-west corner of the entrance to tomb AGH026 together with a group of other cartonnages, also removed from the mummies to which they belonged.The refined design on the head, characterized by a winged scarab holding a golden solar disk between its front legs and a red solar disk that recalls the shen ring, a symbol of eternity, between its back legs, exhibits the great value of this cartonnage.During the restoration, a fingerprint left by the painter was identified among the feathers of the beetle's wings.The rear of the helmet features a djed pillar surmounted by the head of the god Khnum and other geometric motifs.Particularly striking, however, is the rendering of the hair that framed the face.The hairstyle with rigid rows of black curls, rendered geometrically in a plastic way, is typical of female sculptural portraits of the Ptolemaic period, and is a typical dating element of the 1st century BC [17].
The second item (AGH026-B13), also excavated in 2019, is a foot (approximately 42 cm × 40 cm × 26 cm) coming from the same cartonnage nucleus as the previous one.The feet represented are wearing sandals.Traces of gilding are clearly visible both on the laces of the sandals and on the toenails.In front of them, a winged beetle is depicted.The side decoration is geometric except for a border of white rosettes.The soles of the sandals, decorated with geometric motifs, are separated by the stem of a lotus flower whose corolla opens at the front.From a stylistic point of view, the object could be dated between the 1st century BC and the 1st AD.The first artifact (AGH026-B14) was discovered in the 2019 excavation campaign.It is a cartonnage helmet, approximately 22 cm in diameter, from which the mask was removed by looters in ancient times.It is found in the south-west corner of the entrance to tomb AGH026 together with a group of other cartonnages, also removed from the mummies to which they belonged.The refined design on the head, characterized by a winged scarab holding a golden solar disk between its front legs and a red solar disk that recalls the shen ring, a symbol of eternity, between its back legs, exhibits the great value of this cartonnage.During the restoration, a fingerprint left by the painter was identified among the feathers of the beetle's wings.The rear of the helmet features a djed pillar surmounted by the head of the god Khnum and other geometric motifs.Particularly striking, however, is the rendering of the hair that framed the face.The hairstyle with rigid rows of black curls, rendered geometrically in a plastic way, is typical of female sculptural portraits of the Ptolemaic period, and is a typical dating element of the 1st century BC [17].
The second item (AGH026-B13), also excavated in 2019, is a foot (approximately 42 cm × 40 cm × 26 cm) coming from the same cartonnage nucleus as the previous one.The feet represented are wearing sandals.Traces of gilding are clearly visible both on the laces of the sandals and on the toenails.In front of them, a winged beetle is depicted.The side decoration is geometric except for a border of white rosettes.The soles of the sandals, decorated with geometric motifs, are separated by the stem of a lotus flower whose corolla opens at the front.From a stylistic point of view, the object could be dated between the 1st century BC and the 1st AD.

Visible Reflectance Spectroscopy
The first artifact (AGH026-B14) was discovered in the 2019 excavation campaign.It is a cartonnage helmet, approximately 22 cm in diameter, from which the mask was removed by looters in ancient times.It is found in the south-west corner of the entrance to tomb AGH026 together with a group of other cartonnages, also removed from the mummies to which they belonged.The refined design on the head, characterized by a winged scarab holding a golden solar disk between its front legs and a red solar disk that recalls the shen ring, a symbol of eternity, between its back legs, exhibits the great value of this cartonnage.During the restoration, a fingerprint left by the painter was identified among the feathers of the beetle's wings.The rear of the helmet features a djed pillar surmounted by the head of the god Khnum and other geometric motifs.Particularly striking, however, is the rendering of the hair that framed the face.The hairstyle with rigid rows of black curls, rendered geometrically in a plastic way, is typical of female sculptural portraits of the Ptolemaic period, and is a typical dating element of the 1st century BC [17].
The second item (AGH026-B13), also excavated in 2019, is a foot (approximately 42 cm × 40 cm × 26 cm) coming from the same cartonnage nucleus as the previous one.The feet represented are wearing sandals.Traces of gilding are clearly visible both on the laces of the sandals and on the toenails.In front of them, a winged beetle is depicted.The side decoration is geometric except for a border of white rosettes.The soles of the sandals, decorated with geometric motifs, are separated by the stem of a lotus flower whose corolla opens at the front.From a stylistic point of view, the object could be dated between the 1st century BC and the 1st AD.However, as will be discussed further in the text, analyses revealed the use of madder, which suggests the latter date.
The third artifact (AGH026-B31) was also found in the 2019 mission in the south-east corner of the front part of room B of AGH026.It was removed in ancient times causing damage and overlapping with other parts of the same group of cartonnages.Only the lateral part, about 40 cm long, is well preserved.The deceased is here depicted praying before a god represented as a fantasy animal formed by a ram's head surmounted by a solar disk, four wings, and an elongated body in the shape of a bird that walks with four legs ending in the maat feather and that carries the mummified deceased on its tail, a symbolic viaticum towards eternal life.On a topological basis, also, in this case, the artifact can be dated between the 1st century BC and the 1st century AD [18].
The fourth cartonnage (AGH026-B41) was found in the third excavation campaign (May-June 2021).It is the upper, fragmentary part of the so-called "apron".It is depicted with a winged scarab and the winged goddess Nut holding the maat feather in her hands, both symbols of rebirth.Also, in this case, the dating on a typological basis is 1st century BC-1st century AD.
Lastly, two fragments (about 4 × 4 cm) of a so-called "barbottina" cup (AGH032-14) from the descent of tomb AGH032 excavated in 2021 were examined.Other fragments of this object were found at a later stage.This cup takes its name from the band decorated with vegetal elements painted in relief with ceramic liquid, followed by two phases: a second firing to obtain the glossy coating and the white overpainting of some elements.On a typological basis, the object can be dated back to the 1st century BC-1st century AD [19].
The cartonnages, after being found in the tomb, were transported to the warehouse on the eastern bank of Aswan where FTIR analyses were performed, except for cartonnage AGH0026-B41, which was investigated by visible reflectance spectroscopy directly on-site at the excavation.The measurements on the pottery were also conducted on-site.This instrumentation included an ATR/FTIR spectrophotometer and a visible reflectance spectrophotometer.

Instumental Techniques
The spectrophotometric analyses (FTIR measurements and visible reflectance analyses) were all performed with non-destructive/micro-destructive instrumentation on the artifacts (cartonnages and pottery, Table 1) and on fragments that had already fallen from the cartonnages and were present inside the plastic boxes in the Aswan warehouse.Scientific instrumentation was used and managed in extreme and challenging conditions, especially on the excavation, which included very high temperatures (often exceeding 40 • C) and the presence of desert sand, which is particularly dangerous for the instrumentation (Figure 1).

ATR/FTIR Spectroscopy
The investigations were carried out by attenuated total reflection/Fourier infrared (ATR/FTIR) spectroscopy to highlight the nature of the pigments present in the samples.These analyses were performed with a portable FTIR spectrometer (PerkinElmer Spectrum Two) coupled with an ATR accessory (UATR Two) equipped with a diamond crystal.The spectra were acquired on colored micro-fragments in the 4000-400 cm −1 range with a 4 cm −1 resolution.Each spectrum was acquired in transmittance mode with 64 scans.Moreover, the identification was performed by comparing sample spectra with reference materials or other literature spectra [20,21].Although the instrument can be considered portable (or rather transportable), it allows only micro-destructive analysis since it requires the sample to be placed on the diamond crystal of the ATR accessory.
The instrument was used on-site in a temporary location where objects and mummies coming from the excavation were moved (Figure 2).

Vis-RS Spectroscopy
Visible reflectance spectroscopy (Vis-RS) analyses were performed by means of a Konica Minolta CM 2300d portable spectrophotometer.The instrument was calibrated using its 100% reflective white reference and a 0% reflective calibration box in the 400-700 nm range.All the measurements were carried out directly on the samples' surfaces.
The instrument in this case was employed directly on the artifacts at the excavation site.

Vis-RS Spectroscopy
Visible reflectance spectroscopy (Vis-RS) analyses were performed by means of a Konica Minolta CM 2300d portable spectrophotometer.The instrument was calibrated using its 100% reflective white reference and a 0% reflective calibration box in the 400-700 nm range.All the measurements were carried out directly on the samples' surfaces.
The instrument in this case was employed directly on the artifacts at the excavation site.

Optical Microscopy
A Dino-Lite USB microscope equipped with an includable/excludable polarizing filter and directly coupled to a portable PC was employed to analyze, in detail, the surfaces of the cartonnages.

Results and Discussion
Comprehensive archaeometric analyses in an archaeological Egyptian excavation are limited by the unfavorable conditions, such as high temperatures and the presence of sand.
Therefore, the analytical investigations were carried out by easily transportable instruments (FT-IR and Vis-RS) that do not need special customs permissions, such as those mandatory for diagnostic systems using X-ray fluorescence.Nevertheless, a laborious bureaucratic procedure was followed before shipping the instrumentation to Egypt.

CartonnageAGH026-B14
The first investigated artifact, AGH026-B14 (Table 1), was the headwear.ATR/FTIR analyses were carried out on small, detached fragments that were present in the storage box.It was possible to analyze a black and a red-colored fragment (Table 2).

Optical Microscopy
A Dino-Lite USB microscope equipped with an includable/excludable polarizing filter and directly coupled to a portable PC was employed to analyze, in detail, the surfaces of the cartonnages.

Results and Discussion
Comprehensive archaeometric analyses in an archaeological Egyptian excavation are limited by the unfavorable conditions, such as high temperatures and the presence of sand.
Therefore, the analytical investigations were carried out by easily transportable instruments (FT-IR and Vis-RS) that do not need special customs permissions, such as those mandatory for diagnostic systems using X-ray fluorescence.Nevertheless, a laborious bureaucratic procedure was followed before shipping the instrumentation to Egypt.

CartonnageAGH026-B14
The first investigated artifact, AGH026-B14 (Table 1), was the headwear.ATR/FTIR analyses were carried out on small, detached fragments that were present in the storage box.It was possible to analyze a black and a red-colored fragment (Table 2).Detecting black pigments solely by FTIR is typically complex.However, the technique was useful in identifying other species contained in the sample (Figure 3 and Table 2) such as calcium carbonate [20,22,23] and silicates [22,24].Detecting black pigments solely by FTIR is typically complex.However, the technique was useful in identifying other species contained in the sample (Figure 3 and Table 2) such as calcium carbonate [20,22,23] and silicates [22,24].Furthermore, the presence of Egyptian blue mixed with a black hue (possibly a coalbased pigment) could be hypothesized from the signals at 1160 and 1045 cm −1 , together with the band at 1008 cm −1 .Indeed, the presence of this black pigment can only be confirmed by Raman spectroscopy [7,25,26], which was not available on-site.Furthermore, observations by means of a USB microscope were carried out on this cartonnage, indicating blue grains mixed with a black pigment.This confirmed the use of Egyptian blue (Figure 4).It is interesting to note that in other cases the surfaces of the cartonnages were very homogeneous .Furthermore, the presence of Egyptian blue mixed with a black hue (possibly a coalbased pigment) could be hypothesized from the signals at 1160 and 1045 cm −1 , together with the band at 1008 cm −1 .Indeed, the presence of this black pigment can only be confirmed by Raman spectroscopy [7,25,26], which was not available on-site.Furthermore, observations by means of a USB microscope were carried out on this cartonnage, indicating blue grains mixed with a black pigment.This confirmed the use of Egyptian blue (Figure 4).It is interesting to note that in other cases the surfaces of the cartonnages were very homogeneous.Detecting black pigments solely by FTIR is typically complex.However, the technique was useful in identifying other species contained in the sample (Figure 3 and Table 2) such as calcium carbonate [20,22,23] and silicates [22,24].Furthermore, the presence of Egyptian blue mixed with a black hue (possibly a coalbased pigment) could be hypothesized from the signals at 1160 and 1045 cm −1 , together with the band at 1008 cm −1 .Indeed, the presence of this black pigment can only be confirmed by Raman spectroscopy [7,25,26], which was not available on-site.Furthermore, observations by means of a USB microscope were carried out on this cartonnage, indicating blue grains mixed with a black pigment.This confirmed the use of Egyptian blue (Figure 4).It is interesting to note that in other cases the surfaces of the cartonnages were very homogeneous .It is very common to find silicates within pigments, especially earth pigments.Some bands attributed to silicates can be assigned to quartz or to clays, like those of the kaolin group [20][21][22]27,28].Water signals at about 3300 and 1620 and some sharp signals in the range of 3700-3300 due to the hydroxyl group have also been highlighted.Kaolin was identified as a binder added to the preparation layer by other authors [29].In our case, it is noteworthy that kaolin group minerals are present mainly within red-hued pigments while are absent, for example, in the blue-green ones, allowing to exclude their use in the preparatory layer.
In the spectrum, it is also possible to detect the presence of two bands typically attributable to organic matter, i.e., the bands of the symmetric and anti-symmetric C-H stretching mode at about 2925 cm −1 and 2859 cm −1 (further signals due to organic binders could be hidden by others bands).The presence of signals from organic substances deriving from the underlying cartonnage cannot be excluded.In fact, to achieve this technique in Egyptian funerary art, scraps of linen or papyrus were stuck together with plaster or resins and used to make sarcophagi and mummy masks.Once dried, the material could then be painted or gilded [15,30,31].Another signal due to organic substances is the shoulder at about 1320 cm −1 that could be due to carboxylates (most probably calcium carboxylate) present after the degradation of the binder.
Calcium carbonate deriving from the substrate used to realize the cartonnage [7,31] was also highlighted.

Sample 2-B14 (Red)
Infrared spectroscopy is very useful to deduce the nature of red pigments.Indeed, it is possible to observe the characteristic bands of hematite at [26,28,[32][33][34] (Figure 3 and Table 2).In addition, the specific signals of the red ochre pigment, hematite, and clays [24,28] are present.Also particularly evident are the signals due to the presence of some organic matter.
As for sample 1-B14, calcium carbonate from the substrate was present.

CartonnageAGH026-B13
Analyses were carried out, as for the first cartonnage, on small, detached fragments that were present in the storage box of the artifact.In this case, it was possible to analyze blue-green-, dark red-, pink-, gold-, black-, and yellow-colored fragments.
It would be interesting to understand whether this pigment is an altered blue or a hue (blue tending to green) obtained by mixing Egyptian blue with a yellow pigment [35], despite these bands seemingly not being present in the IR spectrum (see further on in the text how this pigment has been identified in sample 6-B13).
In addition, the color and spectrum of the sample could suggest another pigment that may have been applied to the artifact, namely the so-called green frit or Egyptian green, which is also synthetic and obtained using a preparation technique similar to that for Egyptian blue [38].

Sample 2-B13 (Dark Red)
In sample 2-B13, the typical and characteristic bands of hematite were observed (Figure 5) together with typical signals of silicates [28,33].The presence of clay minerals is in accordance with hydroxyl group bands.Calcium carbonate present in the substrate of the artifact was evidenced.Furthermore, there is an evident signal around 1320 cm −1 that is attributable to a carboxylate (see sample 1-B14).

Sample 3-B13 (Pink)
The pink color represents a particular case (sample 3-B13, Figure 5), which shows a signal in the range of 600-1200 cm −1 that could be due to madder (alizarine) [39].This is a natural organic pigment that has also been identified in other cases [40].Alizarine is an organic compound and a historically important prominent dye.It is an anthraquinone originally derived from the root of the madder plant.Moreover, detailed analysis consisting of substance identification by chromatographic methods could not be performed in this case due to the impossibility of collecting the samples and bringing them back to the laboratory.With regards to pigment identification, it is important to mention that in the cartonnage sample having a similar pink hue, studied by multispectral analysis (MSI) in a follow-up campaign (results not presented in this paper), evident fluorescence induced by UV radiation was observed, suggesting the presence of madder as a dye.
For this sample, the presence of gypsum cannot be excluded because of the intense water signal around 3400 cm −1 (the signal due to sulphate around 1100 cm −1 could also be due to gypsum).Finally, the shoulder around 1320 cm −1 is probably ascribable to a carboxylate, as previously highlighted.

Sample 4-B13 (Gold)
The main signals observed for this sample are due to calcium carbonate (Figure 5).Since elemental analysis was not performed, the presence of gold cannot be confirmed.However, a signal at 1652 cm −1 due to a protein-type binder (attributable to amide (I)) that may have been used for gold leaf application can be observed.A very weak silicate signal at about 1000 cm −1 was also highlighted (Figure 5).As described in great detail in the lit-

Sample 3-B13 (Pink)
The pink color represents a particular case (sample 3-B13, Figure 5), which shows a signal in the range of 600-1200 cm −1 that could be due to madder (alizarine) [39].This is a natural organic pigment that has also been identified in other cases [40].Alizarine is an organic compound and a historically important prominent dye.It is an anthraquinone originally derived from the root of the madder plant.Moreover, detailed analysis consisting of substance identification by chromatographic methods could not be performed in this case due to the impossibility of collecting the samples and bringing them back to the laboratory.With regards to pigment identification, it is important to mention that in the cartonnage sample having a similar pink hue, studied by multispectral analysis (MSI) in a follow-up campaign (results not presented in this paper), evident fluorescence induced by UV radiation was observed, suggesting the presence of madder as a dye.
For this sample, the presence of gypsum cannot be excluded because of the intense water signal around 3400 cm −1 (the signal due to sulphate around 1100 cm −1 could also be due to gypsum).Finally, the shoulder around 1320 cm −1 is probably ascribable to a carboxylate, as previously highlighted.

Sample 4-B13 (Gold)
The main signals observed for this sample are due to calcium carbonate (Figure 5).Since elemental analysis was not performed, the presence of gold cannot be confirmed.However, a signal at 1652 cm −1 due to a protein-type binder (attributable to amide (I)) that may have been used for gold leaf application can be observed.A very weak silicate signal at about 1000 cm −1 was also highlighted (Figure 5).As described in great detail in the literature [41], the gold leaf could have been applied to the cartonnage by means of lime plaster (based on calcium carbonate) and organic binders.The so-called bole [42], i.e., clays and thus silicate-based earths, was also used.

Sample 5-B13 (Black)
In the case of the black sample 5-B13, only the nature of the substrate consisting of calcium carbonate and silicates could be identified.
As already mentioned, it is difficult to identify black pigments by FTIR alone.However, it is known that black color in Egyptian art was typically obtained from carbon, using what is known as carbon black.This pigment could be easily recognizable and identifiable using the Raman technique [7,25,26], which was not employed in this study.

Sample 6-B13 (Yellow)
In sample 6-B13 the typical signals of yellow ochre were observed [43] (Figure 5 and Table 3) together with quartz, a mineral contained in yellow ochre [27,43].Calcium carbonate was due to the substrate.

CartonnageAGH026-B31
In this case it was possible to analyze blue-green and red areas on fragments detached from the artifact and present in the storage box, as for the previous samples.

Sample 2-B31 and Sample 3-B31
On sample 2-B31 (Figure 4, Table 4), the characteristic bands of hematite were observed together with clays typical of the red ochre pigment [28,33].Hydroxyl signals confirmed the presence of these minerals.Calcium carbonate is due to the substrate.
The characteristic bands of hematite were also detected in sample 3-B31, thus confirming the presence of red ochre [27,32,34].As for the other red samples (1-B14, 2-B13 and 3-B13), a shoulder around 1320 cm −1 , probably ascribable to a carboxylate resulting from the binder degradation, is evident.

Cartonnage AGH026-B41
In the case of this cartonnage, measurements were carried out directly on-site at the excavation.Unfortunately, it was not possible to transport the fourth cartonnage to the warehouse (where the other cartonnages were stored) due to permission issues.Therefore, the only technique that was transportable on the excavation, i.e., Vis-RS, was used.The analyzed points are highlighted in Figure 7.  On sample 2-B31 (Figure 4, Table 4), the characteristic bands of hematite were observed together with clays typical of the red ochre pigment [28,33].Hydroxyl signals confirmed the presence of these minerals.Calcium carbonate is due to the substrate.
The characteristic bands of hematite were also detected in sample 3-B31, thus confirming the presence of red ochre [27,32,34].As for the other red samples (1-B14, 2-B13 and 3-B13), a shoulder around 1320 cm −1 , probably ascribable to a carboxylate resulting from the binder degradation, is evident.

Cartonnage AGH026-B41
In the case of this cartonnage, measurements were carried out directly on-site at the excavation.Unfortunately, it was not possible to transport the fourth cartonnage to the warehouse (where the other cartonnages were stored) due to permission issues.Therefore, the only technique that was transportable on the excavation, i.e., Vis-RS, was used.The analyzed points are highlighted in Figure 7. Vis-RS measurements were carried out with the portable spectrophotometer that allowed identification of the color of the sample following comparison with reference spectra.Five groups of samples could be identified by observing the obtained spectra (Figure 8).Samples 1c, 2c, 3c, and 4c were black.In fact, the reflectance spectra show the curve close to the x-axis due to light being almost entirely absorbed.The spectra of samples 5c and 6c show the typical shape of red.Nevertheless, a very bright red has a well-marked inflection point [26], whereas the curve obtained is characterized by a smoother change indicating a more yellowish color [43].
Samples 7c and 8c, on the other hand, show the characteristic shape of a blue-green spectrum: in fact, the curve shows higher reflectance values around 540-620 nm [44].
Samples 9c and 10c resemble samples 5c and 6c but with less pronounced inflection points.The values tending to 700 nm are higher, thus indicating a less red and more brownish color.
Finally, spectra 11c and 12c allow us to deduce the presence of a color tending towards yellow, with low reflectance values at low wavelengths that increase as the wavelength increases in a gradual manner, differently than in the case with the red pigments [45,46].
To better highlight differences among the various hues, the reflectance spectra in the visible range were subjected to treatment by principal component analysis (PCA).In Figure 9, the obtained scatter plot is reported.This type of data processing has been widely used in scientific literature to treat spectral data coming from artifacts of historical and artistic interest [47].
From Figure 8 it can be observed that the black and blue-green colors have a similar behavior, while some variability can be observed for red, brown and pink samples.This might be due to the use of different recipes depending on the type of result, and thus color tone, desired.Vis-RS measurements were carried out with the portable spectrophotometer that allowed identification of the color of the sample following comparison with reference spectra.Five groups of samples could be identified by observing the obtained spectra (Figure 8).Samples 1c, 2c, 3c, and 4c were black.In fact, the reflectance spectra show the curve close to the x-axis due to light being almost entirely absorbed.The spectra of samples 5c and 6c show the typical shape of red.Nevertheless, a very bright red has a wellmarked inflection point [26], whereas the curve obtained is characterized by a smoother change indicating a more yellowish color [43].
Samples 7c and 8c, on the other hand, show the characteristic shape of a blue-green spectrum: in fact, the curve shows higher reflectance values around 540-620 nm [44].
Samples 9c and 10c resemble samples 5c and 6c but with less pronounced inflection points.The values tending to 700 nm are higher, thus indicating a less red and more brownish color.
Finally, spectra 11c and 12c allow us to deduce the presence of a color tending towards yellow, with low reflectance values at low wavelengths that increase as the wavelength increases in a gradual manner, differently than in the case with the red pigments [45,46].
To better highlight differences among the various hues, the reflectance spectra in the visible range were subjected to treatment by principal component analysis (PCA).In Figure 9, the obtained scatter plot is reported.This type of data processing has been widely used in scientific literature to treat spectral data coming from artifacts of historical and artistic interest [47].
From Figure 8 it can be observed that the black and blue-green colors have a similar behavior, while some variability can be observed for red, brown and pink samples.This might be due to the use of different recipes depending on the type of result, and thus color tone, desired.

Pottery
Finally, two pottery shards coming from tomb AGH032 were analyzed by means of visible reflectance spectroscopy on-site at the excavation.The analyzed pottery is of interest to the archaeologists since it belongs to the same period as the examined cartonnages.Reflectance spectroscopy was used mainly to illustrate a methodological approach related to possible field analyses that could be performed in the future on other ceramic fragments

Pottery
Finally, two pottery shards coming from tomb AGH032 were analyzed by means of visible reflectance spectroscopy on-site at the excavation.The analyzed pottery is of interest to the archaeologists since it belongs to the same period as the examined cartonnages.Reflectance spectroscopy was used mainly to illustrate a methodological approach related to possible field analyses that could be performed in the future on other ceramic fragments excavated in the tombs.The different examined points are shown in Figure 10.

Pottery
Finally, two pottery shards coming from tomb AGH032 were analyzed by means of visible reflectance spectroscopy on-site at the excavation.The analyzed pottery is of interest to the archaeologists since it belongs to the same period as the examined cartonnages.Reflectance spectroscopy was used mainly to illustrate a methodological approach related to possible field analyses that could be performed in the future on other ceramic fragments excavated in the tombs.The different examined points are shown in Figure 10.Preliminary information regarding the colors of the samples was collected from the reflectance spectra in the visible range (Figure 11) acquired on pottery.
With regards to points POT1, POT2, and POT4, it was possible to identify an s-shaped spectrum typical of red tones [44].In fact, an inflection point is evident around 580 nm in which the curve starts to rise, hence the sample no longer absorbs but reflects the light.
Points POT3 and POT6 appear to also be lighter to the naked eye, appearing almost white.They do not present a marked inflection point but show a smoother curve that rises towards longer wavelengths, indicating a more yellow color.
For point POT5, it can be observed that the spectrum absorbs at almost all wavelengths, corresponding to a darker hue.Preliminary information regarding the colors of the samples was collected from the reflectance spectra in the visible range (Figure 11) acquired on pottery.

Conclusions
On-site scientific investigations, including ATR/FTIR and Vis-RS measurements, have been carried out for the first time on artifacts coming from the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt).The instrumentation was used under very challenging conditions and, since no object could be taken outside of Egypt, a full analytical characterization could not be carried out.Despite these constraints, in some cases it was possible to disclose the palette of the cartonnages.With regards to points POT1, POT2, and POT4, it was possible to identify an s-shaped spectrum typical of red tones [44].In fact, an inflection point is evident around 580 nm in which the curve starts to rise, hence the sample no longer absorbs but reflects the light.
Points POT3 and POT6 appear to also be lighter to the naked eye, appearing almost white.They do not present a marked inflection point but show a smoother curve that rises towards longer wavelengths, indicating a more yellow color.
For point POT5, it can be observed that the spectrum absorbs at almost all wavelengths, corresponding to a darker hue.

Conclusions
On-site scientific investigations, including ATR/FTIR and Vis-RS measurements, have been carried out for the first time on artifacts coming from the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt).The instrumentation was used under very challenging conditions and, since no object could be taken outside of Egypt, a full analytical characterization could not be carried out.Despite these constraints, in some cases it was possible to disclose the palette of the cartonnages.
Three pigments abundantly used at the time (red ochre, yellow ochre, and Egyptian blue) were detected by means of ATR/FTIR investigations.The spectra of the blue-green samples (1-B13 and 1-B31) and those of the red samples (2-B14, 2-B13, 2-B31, 3-B31) are almost perfectly superimposable in all samples.Some differences were observed for the dark blue and black colors.In fact, a mixture of Egyptian blue and carbon black was employed to obtain a blue-black hue (1-B14).
Looking at other samples, such as the pink one, the use of an organic dye, i.e., madder, was hypothesized.This allowed the cartonnage to be dated probably to the first century AD.
It is also worth underlining that the same or similar pigments (except for pink) have been used in the different artifacts.This indicates that the palette remained the same along the manufacturing period considered (the cartonnages studied are all dated between the first century BC and the first century AD).
Reflectance spectroscopy applied on cartonnage AGH026-B41 revealed that the black and blue pigments applied on the artifact are quite similar, while some differences were observed for pink and red hues.
With regards to the two small ceramics, measurements were made exclusively on-site by Vis-RS in order to provide indications that could be useful if the measurements were to be carried out on other ceramic objects found on the excavation.
In the future campaigns, more accurate and detailed on-site investigations will be performed on the artifacts by other complementary instrumentation transportable on-site (i.e., XRF and Raman portable spectroscopy).

Figure 1 .
Figure 1.Some of the researchers at work on the excavation (on the left) and the entrance of tomb AGH026 (on the right).

Figure 1 .
Figure 1.Some of the researchers at work on the excavation (on the left) and the entrance of tomb AGH026 (on the right).

Figure 1 .
Figure 1.Some of the researchers at work on the excavation (on the left) and the entrance of tomb AGH026 (on the right).

Figure 1 .
Figure 1.Some of the researchers at work on the excavation (on the left) and the entrance of tomb AGH026 (on the right).

Figure 2 .
Figure 2. FT-IR spectroscopy measurements at the warehouse where the objects were moved.

Figure 2 .
Figure 2. FT-IR spectroscopy measurements at the warehouse where the objects were moved.

Figure 4 .
Figure 4. Observation of the surface of cartonnage AGH026-B14 carried out by means of a USB microscope (on the left) and an image acquired on a black area where blue grains mixed with the black pigment are evident (on the right).

Figure 4 .
Figure 4. Observation of the surface of cartonnage AGH026-B14 carried out by means of a USB microscope (on the left) and an image acquired on a black area where blue grains mixed with the black pigment are evident (on the right).

Figure 4 .
Figure 4. Observation of the surface of cartonnage AGH026-B14 carried out by means of a USB microscope (on the left) and an image acquired on a black area where blue grains mixed with the black pigment are evident (on the right).

Figure 7 .
Figure 7. Cartonnage AGH026-B41 and the list of the points analyzed by portable visible reflectance spectroscopy.

Figure 7 .
Figure 7. Cartonnage AGH026-B41 and the list of the points analyzed by portable visible reflectance spectroscopy.

Figure 9 .
Figure 9. Scatter plot obtained after PCA analysis carried out on visible reflectance spectra acquired on different points on cartonnage AGH026-B41.

Figure 9 .
Figure 9. Scatter plot obtained after PCA analysis carried out on visible reflectance spectra acquired on different points on cartonnage AGH026-B41.

Figure 10 .
Figure 10.Pottery AGH032-14 and the list of the points analyzed by Vis-RS.

Figure 10 .
Figure 10.Pottery AGH032-14 and the list of the points analyzed by Vis-RS.

Figure 11 .
Figure 11.Visible reflectance spectra of all samples of pottery acquired on the points (POT1-6) indicated in Figure 10.

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List of the analyzed artifacts and the corresponding performed analysis.

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List of the analyzed artifacts and the corresponding performed analysis.

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List of the analyzed artifacts and the corresponding performed analysis.