Minerals and Metals in Ancient India v1.c28.s2: Mortars, Plasters and Pigments
Minerals and Metals in Ancient India v1.c28.s2
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Mortars, Plasters and Pigments
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In ancient India specific mortars were used to join the bricks and plasters to coat the walls. These contained gypsum, lime, clay and sand. Analysis of some of the ancient samples are provided in Table 20.2.
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Rock wall painting in India has a 2000-year old tradition involving the uses of plasters and pigments. Apart from the pre-historic cave paintings in Panchmarhi, Mirzapur etc., we have in the Jogimara caves of the Ramgarh hill the earliest (2nd century BC) paintings of the Historical Period. The Ajaṇṭā murals spanned across the period second century BC to sixth century AD. The dates of other wall paintings in ancient India (up to 12th century AD) and the materials used therein are presented in Table 20.3. Agrawal (1969-70) has studied the material bases of the mural paintings.
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The fourth-fifth century AD text Viṣṇudharmottara Purāṇa (Shah, 1958: 115-16) provided the earliest textual recipes for the paints and the plasters which had to be prepared and applied before painting. The text recommended the use of lime in the plaster along with organic binders such as guggula (Boswellia Serrata gum), madhucchista (beeswax), guḍ (molasses etc.). Often lime used to be mixed with clay or sand. Abhilāṣitārtha Cintāmaṇi (of king Someśvara 12th century AD) recommended vajra-lepa or binding paste containing lime, white clay, moonshine white mineral nāga from the Nilgiris (most probably kaolin) smeared with oil or plant-exudation gums etc. as the plaster before painting.
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Before we refer to the use of pigments, let us mention the applications of lime and gypsum in whitewashing, plasters and mortars. As in Egypt, gypsum was used along with lime in Mohenjo-Daro and Harappa. Table 20.2 shows the analyses of mortars, lime-washes and plasters in the Harappan civilization, Kauśāmbī, Ajantā and seventh-thirteenth century AD samples in ancient India.
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The thin white coatings on the Paraśurāmeśvara and Mukteśvara temples and on the Koṇārka one are very rich in lime content and do not seem to contain any intentionally added sand; these are therefore simple limewashes. The lime-pasters (like the mortars in Mohenjo-Daro) contain substantial portions of sand (and clay); the lime: sand ratios range from 4 : 1, 3 : 1, 2 : 1 to 4 : 3. In the last case, as in the interior of the vimāna of Koṇārka temple, the coarse plaster is about 0.56 cm in thickness. For the plaster of the Liṅgarāja temple which assays 3.12 per cent MgO, dolomitic limestone must have been used after calcination. Despite having small percentages of SO₃, the plaster samples did not have any substantial amount of gypsum. Gypsum, used in Egypt, Mohnejo-Daro and Harappa, were locally available.
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Gairola (1949) also analysed the red paints on the temples and did not find any organic matter therein. These were simple mixtures of local hematitic ochre and clay mixed to give the desired tint. The red paint from the Mukteśvara temple assayed 36.42 per cent Fe₂O₃ and 40.97 per cent sand and clay. A sample of the red ochre collected from the Bhubaneśwar market assayed 58.80 per cent Fe₂O₃ and 28. 90 per cent sand and clay. None of the two samples contained any manganese oxide which is a common impurity in hematite. Thus local red ochre, free from manganese oxide, must have been used and a thick slurry painted with a brush on the ancient temples. Ochres of different shades are available in the Bihar-Orissa region and must have been used in the works of art.
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Analyses of Some Mortars, Lime-washes and Plasters Used in Ancient India (percentages)
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| Sl. No. | Samples | CaSO₄ | CaCO₃ | Clay and Sand | Fe₂O₃ and Al₂O₃ | Clay and Al₂O₃ | SO₃ Sand* | MgO | CO₂ Phases | Alkali Salt |
| 1. | Monhenjo-Daro wall mortar HR-Site | 74.12 | 2.50 | 20.41 | | | | | | 1.18 |
| 2. | Mohenjo-Daro Vat mortar HR-Site | — | 69.58 | 21.71 | | | | | | 5.44 |
| 3. | Kauśāmbi, Plaster | 27.53 | | | | 38.09 | | 1.29 | 23.07 | |
| 4. | Kauśāmbi, mortar | 27.98 | | | | 29.95 | | 1.29 | 23.42 | |
| 5. | Ajaṇṭā, Rough Plaster | 1.00 | | | | 60.00 | | 0.95 | 1.83 | |
| 6. | Lime-wash, Paraśurāmeśvara temple, 7th-8th century AD | 49.22 | | | | 7.27 | 0.63 | 1.14 | 39.38 | |
| 7. | Lime-wash, Mukteśvara temple, 8th century AD | 53.72 | | | | 4.62 | 0.56 | 0.48 | 40.32 | |
| 8. | Plaster, Liṅgarāja temple, 10th century AD | 37.30 | | | | 19.26 | 0.78 | 3.12 | 33.31 | |
| 9. | Plaster, Nālandā Site no. 3 | 33.95 | | | | 27.52 | 0.27 | 1.13 | 25.84 | |
| 10. | Lime-wash, figure on jagamohana, Koṇārka, 13th century AD | 51.16 | | | | 1.46 | 0.50 | 0.24 | 44.24 | |
| 11. | Plaster, interior of vimāna, Koṇārka, 13th century AD | 30.72 | | | | 35.89 | 0.38 | 0.16 | 25.70 | |
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∗ This portion of the sample insoluble in three per cent HCl showed clear particles of sand and clay under microscope.
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*Viṣṇudharmottara Purāṇa* recommended the following pigments for statues and mural paintings: gold, silver, copper, mica, ultramarine, red lead, lead yellow, orpiment, lime, lac vermilion and indigo; the recommended use of astringent probably helped to fix the pigments on the substrate as tannin complexes. *Abhilāṣitārtha Cintāmaṇi* endorsed the use of pulverised gold, conch, cinnabar, lac juice, copper powder, orpiment and lamp black. Agrawal (1969-70: 112-13) summarised the analytical data for the Indian mineral paints, a gist of which is presented in Table 20.3. He also mentioned, on the basis of chemical analysis conducted, the use of additional pigments for wall paintings in ancient India:
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| Red | : | vermilion, red ochre, red lead |
| Yellow | : | yellow ochre, pulverised gold |
| Blue | : | ultramarine, indigo |
| Green | : | terre verte, malachite, chrysocolla |
| White | : | lime, chalk, kaolin |
| Black | : | lamp black, charcoal |
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Oddy *et al.* (1981: 100-01) analysed the pigments on the selected 121 pieces of Tibetan and Himalayan metalworks. A quarter of them were gold-painted. The other pigments used in the twelfth-sixteenth century AD context were subjected to X-ray diffraction analysis and found to be blue azurite, red lead, cinnabar, some amorphous black component etc.