The Goetheanum's single-coloured window panes, their forms cut away with a diamond bit, finished as art only when sunlight passes through.
Engraved Glass Windows in Anthroposophy is the name for the window art Rudolf Steiner devised for the first Goetheanum at Dornach and described in his lecture of 28 December 1921, printed in The Ideas Behind the Building of the Goetheanum (GA 289). Each window starts as one pane of single-coloured glass. The motif is not painted on and not leaded together from fragments: it is scratched out of the coloured surface with a diamond bit, in a method Steiner called Glasgravieren, glass engraving. He held that the finished pane, standing in the workshop, is no more a work of art than a musical score is: the score waits for performance, the pane waits for its wall. The artwork begins when the pane sits in its right place and sunlight comes through. The window is therefore an organ of seeing, not a decoration: at Dornach the wall opens to the cosmos instead of closing the building off.
Engraved glass windows are the coloured panes that close the lower storey of the Goetheanum, each one a single tone of glass with its imagery cut away by a diamond point rather than laid on with pigment. Steiner treated them as unfinished until installation: the sun outside, changing hour by hour, is the co-author. The window is an event, not a picture on a wall.
In Steiner's Own Words
These windows are designed in such a way that they are created from single-coloured glass panes according to a method that one could call glass engraving: a single-coloured glass pane, from which the form is carved out with a diamond bit. This sheet of glass, when it is finished and placed somewhere, is of course not a work of art, any more than a score is a work of art. Only when it is put in its right place and the light of the sun shines through, then the work of art is there. Only with outer nature, with the outer world, does it make sense.
What it Means Today
The claim that an artwork stays unfinished until outer nature completes it has one exact counterpart in recent art. James Turrell, the American light artist, builds rooms he calls Skyspaces: chambers with a clean aperture cut through the ceiling, open to the weather. His Meeting, begun in 1980 and completed in 1986 at MoMA PS1 in Queens, New York, is a bench-lined room whose opening frames a rectangle of sky. Nothing in that room is coloured. The colour arrives at dusk, when the tuned artificial light inside meets the fading daylight and the sky reads as a solid plane. Switch the piece off and it is a plain room, exactly as Steiner's engraved pane in the Glashaus at Dornach was a plain sheet of coloured glass until it went into a wall.
Thalira synthesis: what Steiner and Turrell share is not a style but a refusal, the refusal to let an artwork be portable. A painting can be crated and rehung anywhere without loss. A Goetheanum window and a Skyspace both die in transit, because part of their material is the local sky. The practical consequence at Dornach is a rule of use rather than a matter of taste: go twice, at two different hours, because the same engraved window is not the same window at ten in the morning and at four in the afternoon.
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