CULTURE
Does your Thanjavur have fake gold?
Real glitter:Using gold foil adds to the life of a painting.R.M. RajarathinamThe Hindu
Real glitter:Using gold foil adds to the life of a painting.R.M. RajarathinamThe Hindu
Now there is an easy way to tell without taking it apart — Raman spectroscopy
People have long known that not every Thanjavur painting that glitters is gold. There was, however, no way to find out if the gold foil and gemstones used in these traditional crafts were authentic or fake – not without ruining the painting. Now there is: Raman spectroscopy.
The gold foil used liberally in Thanjavur paintings serves two objectives: the glitter makes the painting more attractive, and it also prolongs the life of the artefact. Foils made of fake material look similar to genuine gold, making it difficult for consumers to tell the difference.
Ramanathan Venkatnarayan from the Department of Chemistry at the Indian Institute of Technology (BHU) Varanasi, and his team of researchers from SASTRA University, Thanjavur, Tamil Nadu have found a solution that uses Raman spectroscopy to tell whether the foil used in the paintings is made of gold or some other cheaper material.
The researchers tested ten ‘gold foils’ and found only three to be genuine. In the case of paintings, only one or two out of ten turned out to be genuine gold foil. The gold foils and paintings (most of them made recently) used in the study were sourced from artisans from in and around Thanjavur.
Art with GI tag
Thanjavur paintings have Geographical Indication tags, which puts a premium on their authenticity, but there are no regulations governing the quality or authenticity.
The researchers validated their detection of fake gold by carrying out an energy dispersive X-ray analysis (EDX) of the paintings, which confirmed the Raman spectroscopy findings. “EDX can also be used to find out if the foil is made of gold. But unlike in the case of EDX, Raman spectroscopy does not require the removal of the frame and the glass,” said Dr. Venkatnarayan, the corresponding author of a paper published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy .
Raman spectroscopy, which helps identify molecules in ‘gold’ foil is attractive as it is non-destructive. “We are working to find out the composition of the fake material,” Dr. Venkatnarayan said.
The research paper also suggested framing of regulations for Thanjavur paintings.
People have long known that not every Thanjavur painting that glitters is gold. There was, however, no way to find out if the gold foil and gemstones used in these traditional crafts were authentic or fake – not without ruining the painting. Now there is: Raman spectroscopy.
The gold foil used liberally in Thanjavur paintings serves two objectives: the glitter makes the painting more attractive, and it also prolongs the life of the artefact. Foils made of fake material look similar to genuine gold, making it difficult for consumers to tell the difference.
Ramanathan Venkatnarayan from the Department of Chemistry at the Indian Institute of Technology (BHU) Varanasi, and his team of researchers from SASTRA University, Thanjavur, Tamil Nadu have found a solution that uses Raman spectroscopy to tell whether the foil used in the paintings is made of gold or some other cheaper material.
The researchers tested ten ‘gold foils’ and found only three to be genuine. In the case of paintings, only one or two out of ten turned out to be genuine gold foil. The gold foils and paintings (most of them made recently) used in the study were sourced from artisans from in and around Thanjavur.
Art with GI tag
Thanjavur paintings have Geographical Indication tags, which puts a premium on their authenticity, but there are no regulations governing the quality or authenticity.
The researchers validated their detection of fake gold by carrying out an energy dispersive X-ray analysis (EDX) of the paintings, which confirmed the Raman spectroscopy findings. “EDX can also be used to find out if the foil is made of gold. But unlike in the case of EDX, Raman spectroscopy does not require the removal of the frame and the glass,” said Dr. Venkatnarayan, the corresponding author of a paper published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy .
Raman spectroscopy, which helps identify molecules in ‘gold’ foil is attractive as it is non-destructive. “We are working to find out the composition of the fake material,” Dr. Venkatnarayan said.
The research paper also suggested framing of regulations for Thanjavur paintings.
Raman spectroscopy
Raman spectroscopy (/ˈrɑːmən/; named after Indian physicist Sir C. V. Raman) is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.
It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy yields similar, but complementary, information.
Typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the illuminated spot is collected with a lens and sent through a monochromator. Elastic scattered radiation at the wavelength corresponding to the laser line (Rayleigh scattering) is filtered out by either a notch filter, edge pass filter, or a band pass filter, while the rest of the collected light is dispersed onto a detector.
Raman spectroscopy (/ˈrɑːmən/; named after Indian physicist Sir C. V. Raman) is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.
It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy yields similar, but complementary, information.
Typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the illuminated spot is collected with a lens and sent through a monochromator. Elastic scattered radiation at the wavelength corresponding to the laser line (Rayleigh scattering) is filtered out by either a notch filter, edge pass filter, or a band pass filter, while the rest of the collected light is dispersed onto a detector.
Tanjore Paintings
Tanjore Painting is one of the most popular forms of classical South Indian painting. It is the native art form of Thanjavur (also known as Tanjore) city of Tamil Nadu. The dense composition, surface richness and vibrant colors of Indian Thanjavur Paintings distinguish them from the other types of paintings. Then, there are embellishments of semi-precious stones, pearls and glass pieces that further add to their appeal. The relief work gives them a three dimensional effect. Tanjore Painting of India originated during the 16th century, under the reign of the Cholas.
Maratha princes, Nayakas, Rajus communities of Tanjore and Trichi and Naidus of Madurai also patronized Indian Thanjavur Paintings from 16th to 18th century. Most of these paintings revolve around the theme of Hindu Gods and Goddesses, along with saints. The main figure is always painted at the center of the painting. Since Tanjore paintings are mainly done on solid wood planks, they are locally known as 'Palagai Padam' (palagai meaning wooden plank and padam meaning picture).
Making of Tanjore Painting
Of the numerous steps involved in the making of a Tanjore Painting, the first involves drawing of the preliminary sketch of the image on the base. The base is made up of a cloth, which is pasted over a wooden base. The second step consists of mixing chalk powder or zinc oxide with water-soluble adhesive and applying it on the base. Thereafter, the drawing is made and ornamented with cut glass, pearls and even semi-precious stones. Laces or threads may also be used to decorate the painting. To further augment the effect, wafer thin sheets of gold are pasted in relief on some parts of the painting, while the other parts are painted in bright colors.
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