In the library at Heide 1, a weatherboard house that used to be home to the gallery’s founders, Sidney Nolan’s 1945 painting Nobody knows anything about my case but myself is propped up on an easel. A pair of wonky eyes stares out from behind a black tin mask – it’s Nolan’s iconic rendering of Ned Kelly, who was the muse for the modernist’s most famous series. Next to the painting there's an Oculus Rift virtual reality headset, an incongruous hunk of black plastic among oak furniture and leather-bound books.

Put the two together and something happens. The headset transports you into a reconstruction of the library, in which you can see beneath Kelly’s helmet to an odd, angular face.

Art conservators from Heide and the Art Gallery of New South Wales have worked with Australian Synchrotron, a research centre, to get a glimpse under Kelly’s head armour. Heide curator Kendrah Morgan and Paula Dredge of the AGNSW had long suspected there was something beneath the finished layers of paint. Synchotron’s fluorescent X-ray beamline proved the canvas had indeed been used before. By cross-referencing the X-ray findings with the paints that Nolan used, Kelly is unmasked.

In Nolan’s Kelly series the bushranger’s identity is always obscured by his mask, which Nolan generally portrayed as a black box. Art historian and noted Nolan fan Sir Kenneth Clark says in a comment displayed next to the painting, "we never see Kelly's face. That is how myths should be created."

The Oculus provides a glimpse into Nolan’s process more than it offers resolution to the mystery of the enigmatic figure inside the mask. In this case, it appears Nolan painted what looks to be a self-portrait (Morgan points out the uncovered painting’s similarity to Nolan’s 1943 Self Portrait), then turned it upside-down for unknown reasons and started again, leaving just the eyes pointing out from behind the helmet.

This isn’t the first time Synchrotron has made this kind of discovery. Last year the technology was used to uncover an Edgar Degas portrait beneath another portrait.

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But this bit of Australian art history, unveiled on the 100th anniversary of Nolan’s birth, and put on show in the very house where Sidney Nolan painted so much of his career-defining Kelly works, is something special.

You’ve got until Sunday to see it.

Sidney Nolan Unmasked is at Heide until May 14.

Broadsheet is a proud media partner of Heidi Museum of Modern Art.