The art news in brief this week.

1. A study has revealed that Damien Hirsts’ notorious tanks of animals in formaldehyde may have been leaking a toxic gas. The journal publishing these findings, Analytic Methods, has revealed that the two sculptures leaking the most amount of gas are Away from the Flock and Mother and Child (Divided) – the exact level of the gas detected around Mother and Child (Divided) was not written in the journal’s article. The study has been led by Pier Giorgio Righetti at the Politecnico di Milano in Italy. Righetti said the research "was intended to test the uses of a new sensor for measuring formaldehyde fumes and we do not believe that our findings suggest any risk to visitors at Tate Modern". Click here to read more on this story.

2. Os Gemeos (the two Portuguese street artists and brothers) have created their first mural in Italy. The large-scale mural is that of a train jumper and has been commissioned by the Pirelli HangarBicocca, a contemporary art museum in Milan. The mural has been titled Efêmero (which translates as Ephemeral) and harks back to when the building was used to build trains during the 20th century. (via Street Art News)

3. According to Italian art detective Silvano Vinceti, the portrait of Mona Lisa (which hangs in the Louvre in Paris) is not just that of the wife of a wealthy cloth merchant as has often been reputed, but an amalgamation of this woman – Lisa del Giocondo also known as Lisa Gherardini – and, reportedly, Gian Giacomo Caprotti, often known by his nickname, Salai – little Devil. Caprotti appeared in a number of Da Vinci’s paintings as a model, in a portrait of St John the Baptist, and the erotic The Incarnate Angel. Though other experts dispute this revelation, Mr Vinceti told The Telegraph: “The Mona Lisa is androgynous – half man and half woman. The painting was based on two models. The first was Lisa Gherardini and the second was Salai, Leonardo’s apprentice.” It would certainly explain ‘her’ air of mystery… (via The Telegraph)

4. It’s been announced by the National Gallery that J.M.W Turner’s The Fighting Temeraire tugged to her last Berth to be broken up (1839) (pictured) will appear on a new £20 note. The painting, which was voted in a BBC Radio 4 poll as the ‘Greatest Painting in Britain’, was of great personal importance to Turner, who did not sell it in his lifetime; and rather bequeathed it to the nation after his death. The note will begin circulation in 2020 and will also featured a self-portrait of Turner from the Tate Britain and quote of his,  “Light is therefore colour.” (via Art Daily)

5. Controversial paintings, reportedly by Francis Bacon, are being sold by the Herrick Gallery in London. The ten works have been rejected as fakes by Bacon’s first catalogue raisonné, which will be published by the artist's estate in June. The 10 works being sold, include two pastels priced respectively at £795,000 ($1.1 million) and eight drawings. Martin Harrison, author of the catalogue raisonné, has entirely rejected the authenticity of six of the drawings already in 2012, saying: “[These works are] pastiches, or even parodies, and profoundly disrespectful of Bacon's authentic body of work," he told a Cambridge court. (via Art Net)