1. Photographic Film constriction
2. The Interaction Between The Film with The
3. The Reaction Between Developer with The
4. The Reaction Between The Film with The fixer
5.Safety On Working In The Dark Room
3. 1. photographic film construction
•Photographic film is sheet of transparent
plastic film base coated on one side with a
gelatin emulsion containing microscopically
small light-sensitive silver halide crystals.
• gelatin(is a translucent, colorless, brittle (when
dry), flavorless solid substance)
There are two types of films
•Panchromatic (sensitive to all colors).
orthochromatic (film sensitive to the three
primary colors, red, green, and blue). films
•A typical photographic film contains tiny
silver halide salts such as silver bromide
•*commonly found as "grains" or crystals
•The crystals are suspended in a gelatin
•The silver bromide is in the form of
crystals, or grains,
7. Parts of film
base and emulsion
• made of a clear polyester material
•does not participate in the image-
•clear, strong, consistent thickness
•Tinted pale blue or blue-gray
•coated on 1 or 2 sides with emulsion
•(single emulsion / double emulsion)
•Protective overcoat layered on top of
•Emulsion is a gelatin containing the
•Emulsion is the “active” layer of film
• Active for image forming
• Consists of many small silver halide
crystals suspended in gelatin.
•The gelatin supports, separates, and
protects the crystals.
10. The interaction between the
film and the light
•These compounds of silver are crystalline
in nature and the crystal size is super tiny
with a slight yellow hue.
•When exposed to light, a micro speck of
pure silver forms. In other words, the
crystal starts to reduce (return to an not
•This is the reaction that happens when
the crystals are hit by a few photons (light).
11. Step 1: Light Activation
•It is not fully understood exactly what
happens during exposure but the energy
released when a photon of light strikes a
silver halide crystal frees an electron from
the bromide ion.
•The former bromide ion is released from
the crystal as bromine and is absorbed by
12. Step 2: Movement of electrons
The free electron moves through the
crystal to a 'sensitivity speck' caused
by imperfections in the crystal
structure or created during the
sensitizing process during
13. Step 3: Deposition of Silver Ions
•This now negatively charged speck attracts
positive silver ions which are neutralized to
form silver atoms.
•If enough silver atoms form at a single point
then a latent image is created.
•The latent image is not visible, even under a
microscope so the only way to tell if it is
present is to chemically develop the film to
reveal the image
14. Exposure to a charged particle
A charged particle
energy to the silver
Latent image specks
15. Interaction of silver bromide with
Ag+Br- (crystal) + hv (radiation) -->
Ag+ + Br + e-
The silver ion can then combine with
the electron to produce a silver
Ag+ + e- --> Ag0
18. The free silver produced in the exposed silver
halide grains constitutes what is referred to
as the "latent image," which is later amplified
by the development process
19. 2. The reaction between developer and
Development - The developing agent gives up
electrons to convert the silver halide grains to
Grains that have been exposed to the radiation
develop more rapidly, but given enough time the
developer will convert all the silver ions into
Proper temperature control is needed to convert
exposed grains to pure silver while keeping
unexposed grains as silver halide crystals.
A developer is a solution that has the
ability to recognize the difference
between exposed and unexposed silver
The developer, having identified
exposed silver salts reduces them to
their two component parts.
The silver component is reduced to
metallic silver and remains imbedded in
21. Developer Solution
(6 Ingredients )
The halogen component is soluble in water and
dissolves away into the waters of the developer
1. Reducing Agent: reduce exposed silver halide
to black metallic silver
2. Activator: softens gelatin, maintains alkaline pH
22. Developer Solution
3. Hardener: prevents damage to the film
from over swelling of gelatin in
4. Preservative: Antioxidant that prevents
oxidation of developer
23. Developer Solution
5. Restrainer: prevents chemical fog
protects crystals from chemicals
6. Solvent: dissolves & ionizes the
24. 4. the reaction between the
film and the mixer
•Next the film is immersed in a fixing
•This bath is a solvent for silver salts
but not a solvent for metallic silver.
•Two fixing solutions are in common
usage, sodium thiosulfate and a
rapid acting ammonium thiosulfate.
•Often called hypo a name derived
from hyposulfite of soda.
28. Wash & Dryer film
Wash: Provide thorough removal of
chemical solutions from the film.
-Archival film quality
Dryer: Removes water from film by blowing
warm, dry air
-Between 120 degrees & 130
29. Anybody who is working in a darkroom should
follow these instructions and get themselves
familiar with these health and safety rules
5.Darkroom General Safety Rules:
•Limit access to the darkroom.
•Only approved persons should be allowed to
work in the room.
•Practice good housekeeping.
•Keep the work area clean and uncluttered to
prevent tripping over hazardous chemical bottles.
•Separate the wet and dry areas.
•Always segregate chemicals. (Don’t store acids
•Use the least toxic chemicals
• Avoid cyanides, heavy metals and
developers containing pyrocatechol
or pyrogallol when possible.
•Do not store chemicals on the floor.
•Do not eat, drink or smoke in the
•The darkroom should be well
•Wear appropriate protective
equipment whenever possible, such
as gloves, goggles, etc.)
• Always wash hands with soap and
warm water after working with
•Know how to use emergency
equipment prior to an actual
•Always Add Acid to water, never
water to acid.
•Keep a spill kit in the darkroom.
•Do not use paper towels or saw
dust to clean up acid spills as this
may cause a fire.
•Pregnant women should not be
exposed to powdered developer.
•Store all chemicals in locations that
will minimize the chance of breakage
•Label all containers.
•Keep all containers and trays closed or covered
when not in use to prevent the release of toxic
•Do not wash any chemicals down the sink
(exceptions noted below).
• All spent chemicals should be placed into an
appropriate waste container. (A container the
same as the one the chemical was originally
shipped in is best).