UCT-CCA Negatives-Mustardo Negatives 8-14-12
The University of Cape Town
NEGATIVE
Centre for Curating the Archive
POSITIVE
The Evolution of Negatives
www.thebetterimage.com
info@thebetterimage.com
Structure of Negatives
NEGATIVE
POSITIVE
Generally Layered
Base - Binder - Final Image Material
Base Materials: Paper - Glass - Plastics
Binders: Paper - Collodion - Gelatin
F.I.M.: Silver - Dyes
Paper Negatives
Paper Negatives
Hill and Adamson: Two Fisherwomen, 1845
from Maria Fernanda Valverde s Photographic Negatives Nature & Evloution…
2012-08 Mustardo, The Better Image
1
Paper Negative
Paper Negative
The Process
Characteristics
• Iodize
• Sensitize with silver nitrate
• Expose the paper
• Develop
• Fix (sodium thiosulfate)
• Wash thoroughly
• Wax (optional)
• Thin flexible paper
• Creases, folds
• Variety of tonalities
Collodion on Glass
Wet Plate Negatives
Collodion on Glass
Wet Plate Negatives
The plates had to be exposed and developed while
still moist with the sensitizing chemistry to achieve
sufficient sensitivity or speed.
Collodion on Glass
Collodion on Glass
Wet Plate Negatives
Wet Plate Negatives
The Process
Characteristics
• Clean the glass
• Coat the glass with iodized collodion
• Sensitize the collodion with silver nitrate
• Expose the plate in camera (quickly)
• Develop the plate
• Fix (sodium thiosulfate)
• Wash thoroughly
• Varnish (optional) but protect
• Often thick glass
• Often rough cut edges
• Evidence of flow marks
• Incomplete coverage
• Signs of applied varnish
• Dull milky brown or brown/gray tonalities
• Eventually make your positive print…
2012-08 Mustardo, The Better Image
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Gelatin on Glass
Gelatin on Glass
Dry Plate Negatives
Dry Plate Negatives
The Process
Characteristics
• Purchase the glass negatives
• Open the box
• Expose the plate in camera
• Develop the plate
• Fix (sodium thiosulfate)
• Wash thoroughly
• Varnish (optional) but protect
• Thin glass
• Very uniform
• Clean edges
• Even, complete coating
• Cold black tonality
• Often now heavily mirrored
Film Based Negatives
Film Based Negatives
The Processes
The Processes
• Cellulose Nitrate
1889 - 1950
• Cellulose Acetates 1925 - today
(diacetate - butyrate - propionate - tri-acetate)
• Polyester
1955 - today
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
Film Based Negatives
Cellulose Nitrate - Stages of Deterioration
• Support yellows and shows silver mirroring
• Becomes sticky and gives off nitric acid aroma
• Image darkens and begins to fade
• Film softens and becomes adhesive
• Turns into brown acidic powder
Curling
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Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
Film Based Negatives
Cellulose Acetate - Stages of Deterioration
SAFETY FILM
• Shrinkage and acetic acid aroma (vinegar)
• Begins to warp and may show blue or pink staining
• Bubbles and crystaline deposits form between layers
• Channels form
• Unprintable
Film Based Negatives
Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
www.albumenworks.com
2012-08 Mustardo, The Better Image
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Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
www.albumenworks.com
Film Based Negatives
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
www.albumenworks.com
Film Based Negatives
The Processes
• Cellulose Nitrate
• Cellulose Acetates
• Polyester
2012-08 Mustardo, The Better Image
THE END
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