Head VI was the first of Bacon 's paintings to reference Velázquez , whose portrait of Pope Innocent X haunted him throughout his career and inspired his series of " screaming popes " , a loose series of which there are around 45 surviving individual works . Head VI contains many motifs that were to reappear in Bacon 's work . The hanging object , which may be a light switch or curtain tassel , can be found even in his late paintings . The geometric cage is a motif that appears as late as his 1985 – 86 masterpiece , Study for a Self @-@ Portrait — Triptych .