Self-portrait - Janez Puhar
Photo: Tina Kosec/BOBO
Janez Puhar is not the general inventor of photography and built on the already known daguerreotype. However, he developed a unique process and significantly reduced the cost of production and considerably shortened the exposure time. This year marks the 210th anniversary of his birth and 160 years of his death (August 26, 1814, Kranj – August 7, 1864, Kranj).
Puharotype / Heliotype
In his photographic work, Puhar used only material that was cheap and could be obtained everywhere: glass plates, bromine, sulfur, iodine, mercury and alcohol. He covered the process of taking photographs on a glass plate, which he coated with a thin layer of sulfur and then exposed to iodine vapor. The product was then fixed in alcohol. We have several names for this: feather type, heliotype, hyalotype, light type, translucent daguerreotype on glass. Unfortunately, he could not present the invention to the public because he did not know how to simplify it and because of its toxicity. The exposure time was much shorter than in the experiments of contemporaries - only fifteen minutes. Puharotype differs from other related inventions in its manufacturing process, which is toxic. It was a one-step process. In doing so, a latent image (negative) was formed on the glass, which was already developing under steam. Puhar discovered that a positive is reflected if the image is lined with a dark background. There is only one original here.
Puhar thus made a major, pioneering contribution to the history of photography. He was already using emulsion reversal and darkening of the back side of the photo. In official circles, he is not considered the inventor of the daguerreotype on glass, but Abel Niepce De St. is recognized for it. Victor, but both inventors worked in ignorance of each other. Puhar's works are kept by the National Museum in Ljubljana.
Process
In the light, Puhar cleaned a small plate of ordinary glass. Then he lit a sulfur candle, which was his specialty. He mixed the sulfur with mastic, a natural resin that is sticky and dissolves in alcohol or ether. With this mixture, he impregnated a piece of flambable slag. He put the candle made in this way into a narrow metal tube that let in enough air for it to burn. Sulfur fumes rose and covered the glass plate that Puhar held over the flame. The panel was covered with a pearly white coating, it was bluish-red in the translucent light.
In a darkened room, he exposed a glass plate covered with a transparent layer of sulfur to iodine vapors. He inserted the glass plate prepared in this way into the holder on the back of the camera. In the light, Puhar chose his motive. He adjusted the focus with the movable part of the background of the photographic camera. He then poured the mercury into a metal container and placed it on the metal bottom of his camera. He heated the mercury so that it began to vaporize. Puhar's objective was a large lens made of ordinary glass with a focal length of two inches.
He illuminated the thus prepared plate in the photographic camera; a minute at the beginning, but only 15 seconds later. The chemical process in which mercury vapor settled on the illuminated places thus began to take place. When illuminated, more mercury settled on those places on the plate where more light fell. The camera created a weak image on the glass. That is why he had to strengthen the weak mercury picture on a sulphur-iodine base in a darkened room with bromine vapors. He fixed the resulting negative image on glass in alcohol. His photographic process was a dry photographic process, he worked only with vapors and did not use a bath. The whole process took 5 to 8 minutes.
He got a negative in a nice bluish tone. According to Puhar's instructions, the pictures were exhibited against a dark background, as this was the only way the eye could recognize his original negative image on glass as a positive. Puhar secured the painting layer with a veneer and rotated the glass panel with the painting in such a way that it got the correct position of the motif from left to right. At that time, in the age of the daguerreotype, whose drawback was the irregular position of the motif, this was an extraordinary innovation. He additionally protected the picture from moisture and dust by laying another piece of glass and gluing the edges. Each picture on the glass was unique.
Puhar was constantly perfecting the process. Later, he replaced the term heliotype with the term hyalotype, which means a picture on glass or photolithography, later photolithography. To date, no one has been able to restore his process. Inventor Janez Puhar thus still remains a mystery.
In 1839, John Herschel made the first negative on glass, but his process was difficult to reproduce. The Slovenian Janez Puhar invented the process of making photographs on glass in 1841; it was presented to the public on June 17, 1852 in Paris - Académie Nationale Agricole. In 1847, Nicephore Niépce's cousin, the chemist Abel Niépce de St. Victor published his process for making a glass plate and used egg white for the emulsion.
