The games of childhood were a favourite theme with Mercier and he often painted children playing soldiers, cup and ball and cards. He also produced a number of portraits of children blowing bubbles including 'A boy and girl blowing bubbles' (Mrs Michael Freeman, Detroit, in 1976) and 'Three children blowing bubbles' (1747, Mrs J.T. Christie). In the latter, one of the children holds a piece of paper inscribed 'sic transit Gloria Mundi', compounding the theme of vanitas implicit in pictures of such transient objects.
Mercier, born in Berlin, probably came to England in 1716. His most important English patrons were the Hanoverian courtiers and on the arrival of Frederick, Prince of Wales from Hanover, Mercier became his 'Principal Portrait Painter' and 'Library Keeper'. In 1733 Mercier painted his celebrated conversation piece, 'The Music Party' (Royal Collection, Windsor Castle), showing Frederick and his sisters making music in Kew Gardens. He settled in York between 1739-51 and painted many of the Yorkshire gentry but returned to London where he died in 1760.