Gelatin Printed-Out-Prints
(POPs)
Image taken from: http://www.graphicsatlas.org/media/images/GelatinPOP_ID_Tone4_Fullscreen.jpg
Inventor(s)
The invention of Gelatin Printed-Out-Prints (POPs) results
from the coming together of multiple technologies by the work of several
men. In 1871 an English physician named
Richard Leach Maddox introduced gelatin emulsions to the world as an
alternative to—and improvement on—the wet collodion process.[i] Improvements made by Richard Kennett in 1873
and Charles Harper Bennett in 1878 allowed for Maddox’s process to really take
flight.[ii] Several other inventors, including Peter
Mawdsley, Josef Marie Eder, Giuseppe Pizzighelli, and Sir William de Wiveleslie
Abney, can all be credited with important contributions to the research and
development of the silver gelatin photographic process.[iii] The invention of the baryta layer (an
important layer in a silver gelatin POP) is attributed to José Martinez-Sanchez
and Jean Laurent in 1866.[iv]
The first printing-out paper was developed in Munich
in 1867 by Emil Obernetter, and was coated with a collodio-chloride emulsion.[v] In 1885 his son, Johann Baptist Obernetter,
developed a similar paper using a gelatin emulsion.[vi] It is here we really have the birth of the
gelatin POP.
As somewhat of a side-note, it isn’t until 1891 that the
term “printing-out paper” (and the subsequent acronym POP) is first used by the
Ilford Company to describe this kind of paper.[vii]
The Basics
Gelatin POPs were commonly used between 1885 and 1910.[viii] The “printing-out” process itself refers to
the fact that when exposed directly to light the image will gradually appear on
the paper; there is no developing required.[ix]
The
Layers of a Gelatin POP:
The bottom layer of a gelatin POP
will be the paper substrate; then comes
the baryta
layer; then a layer of silver (toned) particles in gelatin (the matting
agent);
and finally a layer surface coating on top.[x]
The Silver Gelatin POP Process:
1. Printing-out paper is placed
under a negative into a special copy frame.
2. The copy frame is exposed to
light (either daylight or artificial light) until the image is developed to the
desired image intensity. Guides for approximate exposure times were usually
available from the paper manufacturers for various lighting conditions.
3. The exposed POP is washed in a
water bath to remove any excess of soluble silver salts.
4. The washed POP is then toned
using different types of gold and platinum toners; or using first a gold, then
a platinum toner.
5. The toned POP is washed again
to remove toning chemicals and fixed using the standard hypo (sodium
thiosulfate) fixer.
6. The toned and fixed photograph
is thoroughly washed in running water or in multiple water changes in a water
tray.
7. The washed photograph is air
dried or surface polished by squeegeeing the print on a clean, polished glass
and letting it dry. The fully dried photograph will usually separates from the
glass surface on its own.
8. Many dried POPs are then
retouched and mounted on a more sturdy paper or paper board support.
9. Some POPS are also varnished or
surface coated to modify their appearance and/or protect them from physical and
environmental damage.[xi]
Uses
The development of the sliver gelatin POP process helped
satisfy the need for “easy” photographic printing from both large-format and
small-format cameras.[xii] The POP paper was sensitive enough that it
could be exposed to daylight, as well as artificial light such as gas lights,
kerosene lamps, or early electrical lightbulbs (without needing the total
darkness of a darkroom), and the image would still come out.[xiii]
Gelatin POPs were most commonly produced as “cabinet cards;”
which are a 4.25” x 6.5” paperboard mount format.[xiv]
The process was widely used for commercial portraiture in the 1890s.[xv] Another application of the POP papers was as image-proofing materials to assess the quality of
negatives.[xvi]
How to Identify
As with all silver printing-out processes, gelatin POPs have
a reddish-brown image color when printed out; however, most were also toned,
usually with gold, which changed the color to more of a purplish-brown.[xvii] Over time, most gelatin POPs are subject to
some level of sulfiding—a process in which residual sodium thiosulfate (the
fixer) causes the image to turn greenish to yellowish-brown, accompanied by
fading.[xviii] Early gelatin POPs were made with glossy, or occasionally
matte, surfaces; after the start of the twentieth century more textures became
available.[xix] This can be a way to approximately date
gelatin POPs. Gelatin POPs can somewhat
resemble albumen prints because of their purplish-brown color; however, at 30X
magnification they can easily be distinguished from albumen by the presence of
a smooth baryta layer which hides all traces of paper fibers.[xx]
Preservation Concerns
There were three types of surface finishing treatments used
with gelatin POPs: matte drying, ferrotyping (where a wet print was dried in
contact with a highly polished surface like metal or glass), and burnishing.[xxi] Each of these has their own problems. Ferrotyped POPs were more brittle and more
prone to cracking than air-dried surfaces.[xxii] As with all prints with gelatin binders,
unmounted gelatin POPs often curled under various conditions. Curling occurs inward under dry conditions
and outward under humid conditions.[xxiii]
A common form of deterioration in gelatin POPs is surface
abrasion. This was most serious with
mounted and burnished prints.[xxiv]
As mentioned earlier, gelatin POPs start out with a
reddish-brown or purplish-brown appearance, but when exposed to moisture and
oxidants over time, the image will fade and become more yellowish-brown. Sulfiding deterioration is more common in
gelatin POPs over albumen prints because its thicker support and baryta layer
tend to hold more thiosulfate than albumen prints do.[xxv] This leads to the very distinctive greenish
to yellowish-brown image color of older gelatin POPs. If the print was washed very well and
there was less thiosulfate retained, and if the print has been kept
under very dry conditions, it’s possible to have an image that has not been
completely faded.[xxvi]
[ii] Ibid. p. 124
[iii] Stulik, Dusan C., and Art Kaplan. “Silver Gelatin.” In The Atlas of
Analytical
Signatures of Photographic Processes. The Getty Conservation Institute, 2013.
las_silver_gelatin.pdf:
p. 4
[iv] Ibid.
[v] Newhall, Beaumont. The History of Photography. New York: The Museum of Modern
Art, 1982: p.126
[vi] Ibid.
[vii] Coe, Brian, and Mark Haworth-Booth. A Guide To Early Photographic
Processes.
England: The Victoria and Albert Museum in association with Hurtwood Press,
1983: p. 23
[viii] “Gelatin POP.” Graphics Atlas. Image Permanence Institue,
2015.
[ix] Coe, Brian, and Mark Haworth-Booth. A Guide To Early Photographic
Processes.
England: The Victoria and Albert Museum in association with Hurtwood Press,
1983: p. 23
[x] Stulik, Dusan C., and Art Kaplan. “Silver Gelatin.” In The Atlas of
Analytical
Signatures of Photographic Processes. The Getty Conservation Institute, 2013.
las_silver_gelatin.pdf:
p. 7
[xi] Ibid. pp.5-6
[xii] Ibid. pp.6-7
[xiii] Ibid. p. 7
[xiv] “Gelatin POP.” Graphics Atlas. Image Permanence Institue,
2015.
[xvi] Stulik, Dusan C., and Art Kaplan. “Silver Gelatin.” In The Atlas of
Analytical
Signatures of Photographic Processes. The Getty Conservation Institute, 2013.
las_silver_gelatin.pdf:
p. 7
[xvii] Coe, Brian, and Mark Haworth-Booth. A Guide To Early Photographic
Processes.
England: The Victoria and Albert Museum in association with Hurtwood Press,
1983: p. 23
[xviii] “Gelatin POP.” Graphics Atlas. Image Permanence Institue,
2015.
[xix] Stulik, Dusan C., and Art Kaplan. “Silver Gelatin.” In The Atlas of
Analytical
Signatures of Photographic Processes. The Getty Conservation Institute, 2013.
las_silver_gelatin.pdf:
p. 8
[xx] Reilly, James M.. Care and Identification of 19th-Century
Photographic Prints. USA:
Eastman Kodak Company, 1986: p. 67
[xxi] Ibid. pp. 44-45
[xxii] Ibid. p. 44
[xxiii] Ibid. p. 45
[xxiv] Ibid.
[xxv] Ibid.
[xxvi] Ibid.
Bibliography
Coe, Brian, and Mark
Haworth-Booth. A Guide To Early Photographic Processes.
England: The Victoria and Albert Museum in association with Hurtwood Press,
1983.
“Gelatin POP.” Graphics Atlas.
Image Permanence Institue, 2015.
Newhall, Beaumont. The
History of Photography. New York: The Museum of Modern
Art, 1982.
Reilly, James M.. Care
and Identification of 19th-Century Photographic Prints. USA:
Eastman Kodak Company, 1986.
Stulik, Dusan C., and Art
Kaplan. “Silver Gelatin.” In The Atlas of Analytical Signatures
of Photographic Processes. The Getty Conservation Institute, 2013.
las_silver_gelatin.pdf
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