When conservators lifted Odilon Redon's library panels at the Abbaye de Fontfroide for loan earlier this year, they found small trial drawings by the Symbolist painter on the wall behind them, hidden for more than a century. The find came to light as La Nuit was taken down, the first time the panels had left the library since installation.

The three panels, La Jour, La Nuit and Le Silence, were finished and put in place in 1911 for collector Gustave Fayet, who had bought the 11th-century former monastery in 1908. They are now heading to Paris for a Fondation Louis Vuitton show devoted to Fayet; the exhibition gathers roughly 250 of the 750 works that once passed through his hands.

What makes the wall sketches puzzling is how little they look like the finished panels. The figures are far smaller, the two women modelled on Redon's wife Madeleine and daughter Simone measure only about 30 to 35 centimetres on the wall, and the colours are brighter than the final works. Abbaye director Alexandre d'Andoque de Sériège, Fayet's grandson, doubts they were a fresco trial: a full fresco would have demanded a long stay and gruelling physical work, and he believes Redon painted them for pleasure, most likely during a ten-day visit in March 1910, when the restored library let him judge how the commission would sit in the room and the window light.

Fayet and Redon had known each other since 1900, and Fayet eventually owned around 300 of the artist's works. He bought Fontfroide partly to save it: after a 1901 law suppressed religious orders and seized their property, historic sites were being sold off for their stone, and Fayet, outbidding rivals, paid 49,925 francs for the abbey in January 1908. The panels are said to be the only Redon decorations still in their original setting in France, and the Paris loan, which needed special authorisation from the culture ministry, will be their first and only time away; afterwards they return to Fontfroide, where the director says the abbey must do far more to tell visitors who Fayet was.