**3. Methodological approach and principle of the physico-chemical analysis plan for materials taken from museum objects**

The success of a heritage approach requires a preliminary or even permanent interaction with the holders of endogenous knowledge and skills. To this end, an ethnobotanical study was carried out on the materials historically used in the making of cultural heritage objects in the region of southern Benin [6]. The target of this survey was mainly aimed at artisans and artists as well as resource persons invested in local cultural awareness. This is a survey based on a semi-structured interview, followed by demonstration sessions on the use of natural materials used by the craftsman, as well as their harvesting for analytical purposes. The analysis plan used is based on a succession of physicochemical analysis techniques which consist in promoting, at each stage, the choice of the appropriate method for the rest of the analysis. This procedure made it possible to reduce the number of experiments to be carried out on the samples taken while increasing the quality of the results obtained. Indeed, very small quantities of dye material the size of a pinhead, are taken from the sampled objects. Then, using a binocular magnifier, the pigments are sorted in order to have the best homogeneous material which is analyzed using an infrared Fourier transform spectrometer (IR-TF) [7]. The interpretation of the results obtained, and their comparison to direct witnesses or to the IR-TF database, conditions the choice of the following analysis. Thus, the coloring matter undergoes either microchemical tests to complete or confirm the results derived from the IR for the inorganic compounds, or an HPLC analysis with a view to identifying the organic dyes. The schematic summary of the sample analysis plan is presented in **Figure 1**.

The IR-TF analysis consists in preparing translucent KBr pellets from the materials taken from the objects, which are subjected to the beam of a spectrometer (Nicolet AVATAR Thermo-360 FT-IR, DTGS KBr detector/OMNIC treatment version 6.0/ acquisition of 64 scans). Colored textiles are directly subjected to the infrared beam in ATR mode. IR-TF spectra were collected in the mid infrared (400–4000 cm<sup>−</sup><sup>1</sup> ).

Microchemical analysis consists in highlighting the constituent ions of mineral pigments. It is carried out by the wet route in a drop of solution under a binocular magnifier. The detection of iron(II) was carried out by reaction with thiocyanate (KSCN, 160 g L<sup>−</sup><sup>1</sup> ) in an acid medium according to the conventional protocol [11]. That of iron(III) was confirmed by reaction with potassium ferricyanide (K3[Fe(CN)6], 100 g L<sup>−</sup><sup>1</sup> ) in an acid medium [12]. The presence of the sulfide ions S2<sup>−</sup> was visualized in an acid medium by reaction with the addition of the reagent iodine-sodium azide and that of the Al3+ ions by the addition of the acetic buffer and

*Heritage*

The recurring problem with ethnographic collections is linked to the lack of documentation or its imprecision, particularly for objects collected in the past [4]. The example of the objects presented in this work is indicative of these shortcomings. However, it has been clarified, according to certain inscriptions and/or characteristics of representation, that these are objects collected around 1900 and coming from the Yoruba-Nago region currently located on the territory of the Republic of Benin. These objects belong to the collections of two museums located in the city of Lyon-France; it is about the African museum and the museum of Confluences. These objects are particularly important because beyond the esthetics, they were all intended for a specific use in their locality of origin. Indeed, the Guèlèdè masks, the Ibéji statuettes, the Shango or hunter costumes ..., worn during specific rituals, or other propitiatory ceremonies increase the spiritual vision of the wearer. This shows, in fact, that ethnic objects remain characterized by the genius of assembling or mixing materials, and

In recent decades, ethnic objects have gained value by circulating between galleries, auction houses and foreign museums; it is important to safeguard and enhance the objects of Beninese cultural heritage in this flourishing art market. To this end, an ethnobotanical survey was therefore carried out upstream, with

the aim of selecting as well as characterizing the coloring principles of the dye plants most used in South Benin in the making of artistic and craft objects [5, 6], followed by an analytical chemical study by Liquid Chromatography (HPLC-UVvisible), by infrared spectroscopy and *via* microchemical tests of dye materials taken from ancient ethnic objects, in order to identify their matrix origin [7]. Overall, this paper is a social and scientific contribution to the knowledge of natural dyes and materials historically used in the artistic field in Benin in order to improve

and revive, ultimately, knowledge of traditional skills as well than for better

We cannot separate the historical context of the chemical characterization of the materials formerly used by African artisans and artists in the making of cultural heritage objects, in particular with regard to the identification and the geographical origin of the objects that have been deported, sold or exchanged. Indeed, works of art from the African continent were formerly relegated to second place, calling them gross or magical. In 1898, the Great Encyclopedia affirmed that "Among the Negroes who seem, however, like all the races of central and southern Africa, very backward in matters of Art, we find idols representing men and reproducing with a grotesque fidelity the characters of the Negro race" [8]. This attitude of Eurocentric academics, which consisted in classing peoples according to their level of artistic technicality, can be explained for a reason which is twofold: the lack of written documents capable of allowing a study is the first; the second finds its foundation in slavery and colonization. A few decades later, voices were raised against this mechanical determinism; this is the case of R. Andree cited by Laude (1988) [9]. The latter mentions in his book that in 1885 Andree wrote that: "Peoples situated at a lower degree of culture may have reached a relatively high degree in the field of art, [...] it does not appear not always as the highest state in the evolution of a people". It follows a material influx from Europe on the question of Negro art which generates more curiosity. Indeed, the Europeans will be interested in the products of the civilization of the negroes which they bought in mass and accumulated them in their museums. At the same time, some missionaries (SMA: Society of African Missions) collected these objects, most of which were described as fetishes and which they deported to Europe. This

conservation-restoration of heritage objects.

**2. Historical overview on ethnic objects**

moreover by the genius of the expression of matter and of the verb.

**22**

#### **Figure 1.**

*Schematic principle of the physico-chemical analysis plan for materials taken from museum objects.*

of aluminon III according to the protocol of Odegaard et al. [13]. The recognition of the binders was carried out by means of the experiment on the heating plate [12].

Regarding the identification of organic dyes by HPLC, the samples were prepared according to the nature of the pigment, favoring a non-denaturing decomplexation method of Bourhis et al. [14]. In fact, the dye material taken from the objects was treated with an acetic buffer solution (pH = 4.3) and then subjected to ultrasound (SOLEX 180 prototype). However, the colored textiles are extracted directly with the mixture of methanol-dimethylformamide solvent (MeOH-DMF, 1:1; v/v). The extract obtained is filtered, evaporated to dryness and then taken up in methanol before being injected into the system. The prototype used includes a Waters 600 quaternary gradient pump, equipped with an autosampler and a Waters 2996 photodiode array detector (PDA). The stationary phase used is a C18-e column (Symmetry Shield RP-18, Waters 5 μm; 4.6 × 250 mm) and the mobile phase consists of a binary mixture of solvents, acetonitrile-water acidified with TFA (0.01%) in gradient mode. The compounds were detected between 190 and 800 nm and the data were processed under control of Empower 2 software.

Overall, the references used for the characterization of materials taken from ethnic objects, consist of coloring principles purified or isolated from the most used dye plants in the region of South Benin, and about 50 commercial standards of phenolic, flavonoid structures, quinones, etc. In addition, the laboratory database contributed in particular to the IR-TF analysis of the samples.

### **4. Ethnobotany survey, a springboard for promoting ethnic objects**

The ethnobotanical survey carried out with resource people, in particular craftsmen and artists, made it possible to draw up a list of natural materials, mainly the dye plants most used in arts and crafts, especially in basketwork, pottery, sculpture, weaving, ..., in southern Benin. Around, 26 plant species belonging to 14 botanical families (**Table 1**) provide various colors usable by these artisans.

These plants were the subject of a report published in 2014 in the journal *Ethnopharmacologia* [6]. The methods of preparing the dyes listed are decoction, grinding, kneading, pressing, crushing, pounding and maceration with the possible addition of mordant. This study revealed that almost 97% of the listed species are also valued for medical care by the respondents, since they are used to treat common ailments such as anemia, malaria, diarrhea and hemorrhoids. In addition, the local Yoruba-Nago names reported for these plants mostly refer

**25**

**Table 1.**

is nearing extinction.

*Cultural Heritage Objects of Southern Benin: Plant Dyes and Exudates Used in Their Confection*

to dye use or the medicinal properties of the plant. This is the case of *Pterocarpus osun* whose vernacular name "osun" refers to the miracles attributed to the soft red substance prepared from this plant. Indeed, this substance is used in the form of an ointment by women right after delivery to announce not only the birth of the baby because of its color but especially for its antifungal properties. It is the same for "Orukpa", local name Yoruba, of the plant *Hymenocardia acida* which literally designates "release of red smoke which kills", because of the toxicity of its wood under the effect of heat. Regarding the indigo dye, it should be mentioned that Benin is distinguished by the low diversity of these blue plants, but also by their quality as well as that of the tank technique used. *Philenoptera cyanescens* (liana indigo) is the most used species accompanied by *Indigofera tinctoria* (indigotier). In addition, in the Yoruba culture (Nigeria and Benin), the application of certain dyes requires special provisions, in particular a good state of purification of the artist so that the dye stays on the support. Sexual intercourse the day before or before dyeing is detrimental to its tenacity. Indigo dye is associated with the worship of a deity named *Iya Mapo* who protects the female world and its activities, such as pottery, oil pressing or soap making. However, it should be noted that this practice

*Directory of dye plants used by artisans and artists in the region of southern Benin.*

*DOI: http://dx.doi.org/10.5772/intechopen.91294*

*Cultural Heritage Objects of Southern Benin: Plant Dyes and Exudates Used in Their Confection DOI: http://dx.doi.org/10.5772/intechopen.91294*


#### **Table 1.**

*Heritage*

**Figure 1.**

of aluminon III according to the protocol of Odegaard et al. [13]. The recognition of the binders was carried out by means of the experiment on the heating plate [12]. Regarding the identification of organic dyes by HPLC, the samples were prepared according to the nature of the pigment, favoring a non-denaturing decomplexation method of Bourhis et al. [14]. In fact, the dye material taken from the objects was treated with an acetic buffer solution (pH = 4.3) and then subjected to ultrasound (SOLEX 180 prototype). However, the colored textiles are extracted directly with the mixture of methanol-dimethylformamide solvent (MeOH-DMF, 1:1; v/v). The extract obtained is filtered, evaporated to dryness and then taken up in methanol before being injected into the system. The prototype used includes a Waters 600 quaternary gradient pump, equipped with an autosampler and a Waters 2996 photodiode array detector (PDA). The stationary phase used is a C18-e column (Symmetry Shield RP-18, Waters 5 μm; 4.6 × 250 mm) and the mobile phase consists of a binary mixture of solvents, acetonitrile-water acidified with TFA (0.01%) in gradient mode. The compounds were detected between 190 and 800 nm and the

*Schematic principle of the physico-chemical analysis plan for materials taken from museum objects.*

Overall, the references used for the characterization of materials taken from ethnic objects, consist of coloring principles purified or isolated from the most used dye plants in the region of South Benin, and about 50 commercial standards of phenolic, flavonoid structures, quinones, etc. In addition, the laboratory database

**4. Ethnobotany survey, a springboard for promoting ethnic objects**

These plants were the subject of a report published in 2014 in the journal *Ethnopharmacologia* [6]. The methods of preparing the dyes listed are decoction, grinding, kneading, pressing, crushing, pounding and maceration with the possible addition of mordant. This study revealed that almost 97% of the listed species are also valued for medical care by the respondents, since they are used to treat common ailments such as anemia, malaria, diarrhea and hemorrhoids. In addition, the local Yoruba-Nago names reported for these plants mostly refer

The ethnobotanical survey carried out with resource people, in particular craftsmen and artists, made it possible to draw up a list of natural materials, mainly the dye plants most used in arts and crafts, especially in basketwork, pottery, sculpture, weaving, ..., in southern Benin. Around, 26 plant species belonging to 14 botanical

data were processed under control of Empower 2 software.

contributed in particular to the IR-TF analysis of the samples.

families (**Table 1**) provide various colors usable by these artisans.

**24**

*Directory of dye plants used by artisans and artists in the region of southern Benin.*

to dye use or the medicinal properties of the plant. This is the case of *Pterocarpus osun* whose vernacular name "osun" refers to the miracles attributed to the soft red substance prepared from this plant. Indeed, this substance is used in the form of an ointment by women right after delivery to announce not only the birth of the baby because of its color but especially for its antifungal properties. It is the same for "Orukpa", local name Yoruba, of the plant *Hymenocardia acida* which literally designates "release of red smoke which kills", because of the toxicity of its wood under the effect of heat. Regarding the indigo dye, it should be mentioned that Benin is distinguished by the low diversity of these blue plants, but also by their quality as well as that of the tank technique used. *Philenoptera cyanescens* (liana indigo) is the most used species accompanied by *Indigofera tinctoria* (indigotier). In addition, in the Yoruba culture (Nigeria and Benin), the application of certain dyes requires special provisions, in particular a good state of purification of the artist so that the dye stays on the support. Sexual intercourse the day before or before dyeing is detrimental to its tenacity. Indigo dye is associated with the worship of a deity named *Iya Mapo* who protects the female world and its activities, such as pottery, oil pressing or soap making. However, it should be noted that this practice is nearing extinction.
