[8] His writings on Abanindranath Tagore and the Santiniketan artists have contributed a new perspective on them by shifting the critical focus from nationalist revivalism to a context sensitive modernism.

Among his curated exhibitions Santiniketan: The Making of a Contextual Modernism commissioned to mark the fifty years of Indian independence, Benodebehari: A Centenary Retrospective (co-curated with Ghulam Mohammed Sheikh) and The Last Harvest : Paintings of Rabindranath Tagore commissioned to mark the 150th birth anniversary of Tagore are considered landmark exhibitions.

The reputed Indian Magazine, Frontline reported, "The best show was the one (celebrating 50 years of Indian Independence) curated by R. Siva Kumar of Santiniketan, 'The Making of a Contextual Modernism', exhibiting about a hundred works each of Nandalal Bose, Rabindranath Tagore, Ram Kinker Baij and Benode Behari Mukherjee".

In a review of Rabindra Chitravali in The Statesman, German scholar Martin Kämpchen (de) writes, "It collects excellently faithful reproductions of Rabindranath's paintings in large format.

Siva Kumar, has spent his entire working life researching the Bengal School of Art, especially the Santiniketan crop of painters.

"[10] For the Royal Asiatic Society, Cambridge Journals, W. Andrew Robinson wrote, "The unparalleled quality of the volumes' reproductions, made from new scans of the original works kept in Santiniketan, in New Delhi and elsewhere, and printed by India's leading art printer, Pragati Offset, based in Hyderabad, is thrillingly good.

An art historical journey that began with and has continuously returned to the work of K. G. Subramanyan, has tracked its course backwards in time to mark out its significant inheritance, not just of the Santiniketan masters (Nandalal Bose, Rabindranath Tagore, Benode Behari Mukherjee and Ramkinkar Baij), but also in the little-known oeuvre of the later Abanindranath.

Those European modernities, projected through a triumphant British colonial power, provoked nationalist responses, equally problematic when they incorporated similar essentialisms.”[16] R. Siva Kumar, being an authority on Tagore's paintings, curator of his largest Exhibition and the author/editor of the most comprehensive reference work on Rabindranath's paintings has played an important role in preventing Tagore-fakes.

In 2011 the Government College of Art and Craft in Kolkata, under principal Dipali Bhattacharya, had organised an exhibition of 23 Tagore paintings.

Siva Kumar, who had already seen digital images of the paintings and, convinced that they were all fakes, had warned the college principal, Dipali Bhattacharya, against holding the exhibition.

Times of India quoted him,"A national-level investigation agency should set up a team of specialists who follow only such cases so that they can see pattern or notice the involvement of same people or part of the same network.

The book presents entire body of Ramkinkar's sketches, watercolours, etchings, oils and sculptures, together with many invaluable period photographs.

[23] Drawing distinction between Benode Behari Mukherjee and Ramkinkar Baij, Siva Kumar notes, "If his friend and colleague Binodebihari painted the starker side of Santiniketan landscape, and saw himself as a lonely palm tree in the middle of the barren and parched Khoai, Ramkinkar saw himself as the Palash in full bloom: No leaves, bare branches, fully ablaze".