The artist Patrick Heron was invited by the architects of Tate St Ives to design a colourful glass window for the new building. The costs were supported by Friends of the Tate Gallery (now Tate Members) and it was installed in March 1993.
The artist and Feary and Heron Architects worked with the glass studio Wilhelm Derix GmbH & Co of Taunusstein, near Franfurt in Germany. The window is made of coloured antique glass sheets laminated onto two large panels of thick clear plate glass. It measure 4.6 by 4 metres.
Heron insisted that the window should not have the usual black leading used in coloured glass windows. This was because his main interest was the exploration of colour and how areas of colour respond in juxtaposition to each other. The colours combine to create a soft purple reflection.
Heron also required that the gridded proportion system should not be symmetrical nor central with the window rectangle. The window is one of the largest unleaded coloured glass windows in the world.
Heron’s design began as a small gouache study. This was then scaled up and translated by Derix into coloured glass. Different combinations of antique glass colours, as well as variations in individual sheets of the same colour, were examined and eventually selected. Today the large north-facing window is set in the Mall.