Rebecca
SGF, Supreme Grumble Framer
Ron's photo posting and Charles's phone tutorials have inspired me. I just finished consolidating/editing my notes on photographs that I use for workshops on preserving family archives, and thought they might be of general interest here. This is the first installment. I am by no means an expert on photos, so if any of you out there are, and have anything to add or correct, please do!
Photographs – survey of common types and problems
Notes for workshop R. Pavitt, draft
Daguerrotypes – 1840’s to mid 1850’s
The first commonly made photographs. The image is developed on a highly polished, silver plated, copper support. These images are very fragile and are protected by a presentation case with glass cover. Daguerrotypes are easily tarnished when the case seal is broken, letting in polluted air.
Ambrotypes – early 1850’s through the 1860’s
These are essentially glass negatives with a black coating on the reverse. The black coating makes the negative appear as a positive. The emulsion layer is collodian, (cellulose nitrate) an early plastic. Like daguerrotypes, ambrotypes are housed in a presentation case. Sometimes the black lacquer backing separates or flakes from the glass.
Cases
Daguerrotypes and ambrotypes cases are made from various materials, including leather, composition, paper mache and fabric. The most typical problems are tears along the hinge or, in the case of daguerrotypes, broken seals.
Tintypes – mid 1850’s though the early 20th century
These images are made from collodian on black lacquered iron. These were very popular because they were fast and easy to make. Some cameras had multiple lenses so that several images could be produced at a time. The carte-de-visite size (2 ½ x 4 inches) was the most popular format. By the 1860’s photo albums with special cutouts were made to hold tintypes. Decorative paper holders were also made to hold single pieces. Tintypes are stable unless bent. This can crack the emulsion and lacquer layers, allowing rust to form.
Albumen photographs – early 1850’s to about 1900
Egg white (albumen) emulsion on very thin paper. The paper is mounted on a paperboard backing for a finished presentation, and to keep them from curling. The backings are often printed with important information regarding the photographic studio where they were made. The albumen binder in these photographs tends to irreversibly yellow, especially when exposed to high humidity. This is caused by a decomposition of sugars and proteins (Maillard reaction). The emulsion is also prone to cracking.
The stability or instability of photographic images has been a problem right from the beginning. In 1847 Punch printed a poem bemoaning this fact:
Behold thy portrait – day by day
I’ve seen its features die;
First the moustacios go away,
Then off the whiskers fly!
Silver is a very reactive material, and the finely divided silver particles found in photographs are quite vulnerable to chemical damage. Typical problems caused by poor processing, high humidity and pollutants (from poor quality contact materials and air borne industrial/combustion contaminants) include fading, yellowing and tarnishing. There were early experiments with more stable pigment techniques – carbon and other pigments were used instead of silver – but these were limited to upmarket portraits and art prints.
Gold and platinum toning, where some of the silver particles are replaced with the more stable toning metal, became one way to stabilize silver images, as well as manipulate the final color of the photograph. Gold toned albumen photographs, for example, have a characteristic purple/brown color. Modern silver gelatin photographs may be selenium toned (cheaper than gold).
(for more info see http://aic.stanford.edu/jaic/articles/jaic38-02-002_2.html)
Gelatin emulsions
Unlike albumen, gelatin is resistant to yellowing (if properly processed). Gelatin emulsions were first used in the 1880’s. Gelatin is a stable binding material, although long term exposure to pollutants can increase its water solubility.
After the 1880’s, gelatin photographs came to include a baryta layer (white barium in gelatin) underneath the emulsion. This layer gives the photograph a smooth reflective surface with bright highlights.
Rebecca
Photographs – survey of common types and problems
Notes for workshop R. Pavitt, draft
Daguerrotypes – 1840’s to mid 1850’s
The first commonly made photographs. The image is developed on a highly polished, silver plated, copper support. These images are very fragile and are protected by a presentation case with glass cover. Daguerrotypes are easily tarnished when the case seal is broken, letting in polluted air.
Ambrotypes – early 1850’s through the 1860’s
These are essentially glass negatives with a black coating on the reverse. The black coating makes the negative appear as a positive. The emulsion layer is collodian, (cellulose nitrate) an early plastic. Like daguerrotypes, ambrotypes are housed in a presentation case. Sometimes the black lacquer backing separates or flakes from the glass.
Cases
Daguerrotypes and ambrotypes cases are made from various materials, including leather, composition, paper mache and fabric. The most typical problems are tears along the hinge or, in the case of daguerrotypes, broken seals.
Tintypes – mid 1850’s though the early 20th century
These images are made from collodian on black lacquered iron. These were very popular because they were fast and easy to make. Some cameras had multiple lenses so that several images could be produced at a time. The carte-de-visite size (2 ½ x 4 inches) was the most popular format. By the 1860’s photo albums with special cutouts were made to hold tintypes. Decorative paper holders were also made to hold single pieces. Tintypes are stable unless bent. This can crack the emulsion and lacquer layers, allowing rust to form.
Albumen photographs – early 1850’s to about 1900
Egg white (albumen) emulsion on very thin paper. The paper is mounted on a paperboard backing for a finished presentation, and to keep them from curling. The backings are often printed with important information regarding the photographic studio where they were made. The albumen binder in these photographs tends to irreversibly yellow, especially when exposed to high humidity. This is caused by a decomposition of sugars and proteins (Maillard reaction). The emulsion is also prone to cracking.
The stability or instability of photographic images has been a problem right from the beginning. In 1847 Punch printed a poem bemoaning this fact:
Behold thy portrait – day by day
I’ve seen its features die;
First the moustacios go away,
Then off the whiskers fly!
Silver is a very reactive material, and the finely divided silver particles found in photographs are quite vulnerable to chemical damage. Typical problems caused by poor processing, high humidity and pollutants (from poor quality contact materials and air borne industrial/combustion contaminants) include fading, yellowing and tarnishing. There were early experiments with more stable pigment techniques – carbon and other pigments were used instead of silver – but these were limited to upmarket portraits and art prints.
Gold and platinum toning, where some of the silver particles are replaced with the more stable toning metal, became one way to stabilize silver images, as well as manipulate the final color of the photograph. Gold toned albumen photographs, for example, have a characteristic purple/brown color. Modern silver gelatin photographs may be selenium toned (cheaper than gold).
(for more info see http://aic.stanford.edu/jaic/articles/jaic38-02-002_2.html)
Gelatin emulsions
Unlike albumen, gelatin is resistant to yellowing (if properly processed). Gelatin emulsions were first used in the 1880’s. Gelatin is a stable binding material, although long term exposure to pollutants can increase its water solubility.
After the 1880’s, gelatin photographs came to include a baryta layer (white barium in gelatin) underneath the emulsion. This layer gives the photograph a smooth reflective surface with bright highlights.
Rebecca