Basically solarigraphic camera is a pinhole camera, very slow one. These pinhole photographs taken with a lensless pinhole camera with a extra long exposure. I use black&white paper which is 5-10 ASA. Exposure time can be very long, in some photos up to six months. Usually average camera is hidden in city for one to two months. The picture will appear without developing photographic paper with any kind of chemicals. Exposured paper is scanned in darkness and developed in Photoshop. All the cameras are very low tech, cheap boxes, canisters or film cans. This method in is antidope for digital photographic madness. I can take only like 5 pictures in month.
Sun draws many interesting traces in photos, you can really see the time passing by. Some times camera is tilted by passerby or tape just goes loose. Double exposures or traces of humidity can be seen in photos.
(via William Gibson's Twitter feed)