OK, the big two oh oh is usually the one you pop the champagne and light the fire crackers for but, you’ve got to admit, a one hundred and seventy-fifth birthday isn’t too bad either. It is one hundred and seventy five years ago that Sir John Herschel discovered the process we are celebrating in this exhibition. All you needed was ammonium ferric citrate, potassium ferricyanide, and light. That was it! It was so simple, but oh, look at that blue. Blue, the most sublime the most pure of all the colours — the colour of the sky, the colour of the ocean when it was smiling, maybe the colour of Heaven, certainly, in its lighter version, the colour of the Virgin’s cloak. A colour so pure and airy, but laid down in that chemical reaction with a ferric fist of iron. Herschel’s amazing discovery of what, on 16 August 1842 he called, chemist that he was, the cyanotype (I would have called it the skyograph, but that may not have caught on) endured and endured. In the twentieth century it became the blueprint. Every steel-girded skyscraper, every streamlined jetliner, started out as cyanotyped lines on an engineer’s diagram. The technical blueprint gave three-dimensional form, through physical construction, to our modernist aspirations. But earlier artists had already discovered that through the magic of light modulation the cyanotype also gave three-dimensional form to physical objects that were laid on the sensitive paper out under the sky. When Anna Atkins laid two specimens of dictyota dichotoma, one in its young state the other in fruit, on cyanotype paper for her book Photographs of British Algae: Cyanotype Impressions she was the first of thousands to discover that the seaweed recorded itself in a magically volumetric way — floating in a virtual space of blueness. One hundred and seventy four years later the seaweed is still suspended there as though not a second has ticked past. How do I know it is dictyota dichotoma? Because Anna Atkins wrote a label, using all of her knowledge of biology, and placed that on the sensitive paper as well. Herschel’s implacable reaction photogrammed Atkins’ Linnaean knowledge and the seaweed’s objective existence together into the same stuff of knowing.

So cut the cake. In a hundred and seventy five years’ time people will still be knowing the world by making cyanotypes. Of that I have no doubt.

My words for ‘Out of the Blue’, curated by Ursula Frederick and Kerry Martin, opening tonight  at Photospace in the ANU School of Art & Design. Featuring work from 1981 by Mazie Karen Turner, Bronwyn Rennex, and others