Talbot’s earliest camera images required exposures of an hour or more, but on September 23, 1840, he made a startling discovery that dramatically increased the medium’s potential. He found that an exposure of mere seconds, leaving no visible trace on the chemically treated paper, nonetheless left a latent image that would appear with the application of an “exciting liquid,” essentially a solution of gallic acid. This discovery, which Talbot patented in February 1841 as the “calotype” process (from the Greek kalos, meaning beautiful), opened up a whole new world of possible subjects for photography. In the days that followed, Talbot trained his camera on various features of Lacock Abbey, his home, and its grounds. Made only a few weeks after his September discovery, this photograph reveals Talbot’s newly found ability to render the tones and textures of masonry and glass and the myriad architectural details of the sixteenth-century corner tower, built by the Abbey’s first lay owner.

Although his September discovery radically transformed his ability to make photographic negatives, his positive prints from those negatives remained tentative, recorded in tones of lilac and lavender (as here) when stabilized with a salt solution, or yellow when stabilized with an iodine solution. Within another year or two he would fix his positive prints with hyposulfite of soda (“hypo”), which yielded more permanent prints rendered in deep chocolate brown tones.