… chose a CLAUDE GLASS (Museum no. P.18-1972), which is a small, treated mirror contained in a box used as a portable drawing and painting aid in the late 18th century by amateur artists. The reflections in it of surrounding scenery were supposed to resemble some of the characteristics of Italian landscapes by the famous 17th-century painter and sketcher Claude Lorrain. The 'glass' consists of a slightly convex blackened mirror, which was carried in the hand and held up to the eye. The mirror's convexity reduced extensive views to the dimensions of a small drawing. The use of a blackened mirror resulted in a somewhat weakened reflection, which stressed the prominent features in the landscape at the expense of detail. It also lowered the colour key.

Upon a Claude Glass

A lady might pretend to fix her face,
but scan the room inside her compact mirror -

so gentlemen would scrutinize this glass
to gaze on Windermere or Rydal Water

and pick their way along the clifftop tracks
intent upon the romance in the box,

keeping untamed nature at their backs,
and some would come to grief upon the rocks.

Don't look so smug. Don't think you're any safer
as you blunder forward through your years

straining to recall some aching pleasure,
or blinded by some private scrim of tears.

I know. My world's encircled by this prop,
though all my life I've tried to force it shut.