‘It glows’: restorer removes queasy look from first world war painting Gassed

John Singer Sargent picture of soldiers blinded by mustard gas, the most popular at the Imperial War Museum, is seen in new light

Since it was unveiled just months after the end of the first world war, John Singer Sargent's monumental painting Gassed has been hailed as an era-defining artwork, going on to be the most popular in the collection of the Imperial War Museum in London.

Enormous in scale - it is more than 6 metres wide - the painting depicts lines of soldiers, blinded by mustard gas, picking their way through a crowded battlefield, each with a hand on the shoulder of the man in front. In later decades many viewers have admired Sargent's uncharacteristic use of a greenish-yellow colour scheme, emphasising the flat khaki of the soldiers' uniforms and perhaps even a queasy atmosphere tinged with poison gas, in which two men lean over to vomit.