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SECTION 11: Photography
Black-and-White Photographic Processing (top)
A wide variety of chemicals are used in black and white
photographic processing. Film
developing is usually done in closed canisters. Print processing uses tray processing, with successive developing
baths, stop baths, fixing baths, and rinse steps. Other treatments include use of hardeners, intensifiers, reducers,
toners, and hypo eliminators.
Mixing Photochemicals (top)
Photochemicals can be bought in liquid form, which only
need diluting, or powder form, which need dissolving and diluting.
Hazards
- Developer solutions and powders are often highly alkaline, and
glacial acetic acid, used in making the stop bath, is also corrosive
by skin
contact, inhalation and ingestion.
- Developer powders are highly toxic by inhalation, and
moderately toxic by skin contact, due to the alkali and
developers themselves (see Developing Baths below).
Precautions
- Use liquid chemistry whenever possible, rather than mixing developing
powders. Pregnant women, in particular, should not
be exposed to powdered developer.
- When mixing powdered developers, use a glove box (a cardboard
box with glass or plexiglas top, and two holes in the sides for
hands and
arms), local exhaust ventilation, or wear a NIOSH-approved toxic
dust respirator.
- Wear gloves, goggles and protective apron when mixing concentrated
photochemicals. Always
add any acid to water, never the reverse.
- In case of skin contact, rinse with lots of water. In case of eye contact, rinse for at least 15-20 minutes, preferably
using an eyewash station, seek medical attention.
- Store concentrated acids and other corrosive chemicals on low
shelves so as to reduce the chance of face or
eye damage in case of breakage and splashing.
- Do not store photographic solutions in glass containers.
Developing Baths (top)
The most commonly used developers are hydroquinone,
monomethyl para-amino phenol sulfate, and phenidone. Several other developers are used for special purposes. Other common components of developing baths
include an accelerator, often sodium carbonate or borax, sodium sulfite
as a preservative, and potassium bromide as a restrainer or antifogging
agent.
Hazards
- Developers are skin and eye irritants, and in many cases strong sensitizers. Monomethyl-p-aminophenol sulfate creates many
skin problems, and allergies to it are frequent (although this is thought
to be due to the presence of para-phenylene diamine as a contaminant). Hydroquinone can cause depigmentation and eye
injury after five or more years of repeated exposure, and is a mutagen.
Some developers also can be absorbed through the skin to cause
severe poisoning (e.g., catechol, pyrogallic acid).
Phenidone is only slightly toxic by skin contact.
- Most developers are moderately to highly toxic by ingestion, with
ingestion of less than one tablespoon of compounds such as monomethyl-p-aminophenol
sulfate, hydroquinone, or pyrocatechol being possibly fatal for adults. Symptoms include ringing in the ears (tinnitus),
nausea, dizziness, muscular twitching, increased respiration, headache,
cyanosis (turning blue from lack of oxygen) due to methemoglobinemia,
delirium, and coma. With
some developers, convulsions also can occur.
- Para-phenylene diamine and some of its derivatives are highly
toxic by skin contact, inhalation, and ingestion.
They cause very severe skin allergies and can be absorbed
through the skin.
- Sodium hydroxide, sodium carbonate, and other alkalis used as
accelerators are highly corrosive by skin contact or ingestion.
This is a particular problem with the pure alkali or
with concentrated stock solutions.
- Potassium bromide is moderately toxic by inhalation or ingestion
and slightly toxic by skin contact.
Symptoms of systemic poisoning include somnolence, depression,
lack of coordination, mental confusion, hallucinations, and
skin rashes
- Sodium sulfite is moderately toxic by ingestion or inhalation,
causing gastric upset, colic, diarrhea, circulatory problems, and
central nervous
system depression. It
is not appreciably toxic by skin contact.
If heated or allowed to stand for a long time in water
or acid, it decomposes to produce sulfur dioxide, which is
highly irritating
by inhalation.
Precautions
- See the section on Mixing Photochemicals for mixing precautions.
- Do not put your bare hands in developer baths.
Use tongs instead. If
developer solution splashes on your skin or eyes immediately
rinse with
lots of water. For eye splashes, continue
rinsing for 15-20 minutes and seek medical attention.
- Do not use para-phenylene diamine or its derivatives if at all
possible.
Stop Baths and Fixer (top)
Stop baths are usually weak solutions of acetic acid. Acetic acid is commonly available as pure glacial
acetic acid or 28% acetic acid. Some
stop baths contain potassium chrome alum as a hardener.
Fixing baths contain sodium thiosulfate ("hypo")
as the fixing agent, and sodium sulfite and sodium bisulfite as a preservative.
Fixing baths also may also contain alum (potassium aluminum sulfate)
as a hardener and boric acid as a buffer.
Hazards
- Acetic acid, in concentrated solutions, is highly toxic by inhalation,
skin contact, and ingestion. It
can cause dermatitis and ulcers, and can strongly irritate the mucous
membranes. The final stop bath is only slightly hazardous
by skin contact. Continual
inhalation of acetic acid vapors, even from the stop bath, may
cause chronic bronchitis.
- Potassium chrome alum or chrome alum (potassium chromium sulfate)
is moderately toxic by skin contact and inhalation, causing dermatitis
and allergies.
- In powder form, sodium thiosulfate is not significantly toxic
by skin contact. By ingestion
it has a purging effect on the bowels.
Upon heating or long standing in solution, it can decompose
to form highly toxic sulfur dioxide, which can cause chronic
lung problems. Many asthmatics are particularly sensitive to sulfur dioxide.
- Sodium bisulfite decomposes to form sulfur dioxide if the fixing
bath contains boric acid, or if acetic acid is transferred to the
fixing
bath on the surface of the print.
- Alum (potassium aluminum sulfate) is only slightly toxic. It may cause skin allergies or irritation.
- Boric acid is moderately toxic by ingestion or inhalation and
slightly toxic by skin contact (unless the skin is abraded or burned,
in which
case it can be highly toxic).
Precautions
- All darkrooms require good ventilation to control the level of acetic acid vapors and sulfur dioxide gas
produced in photography.
- Wear gloves and goggles.
- Cover all baths when not in use to prevent evaporation or release
of toxic vapors and gases.
Intensifiers and Reducers (top)
A common after-treatment of negatives (and occasionally
prints) is either intensification or reduction. Common intensifiers include hydrochloric acid and potassium dichromate,
or potassium chlorochromate. Mercuric
chloride followed by ammonia or sodium sulfite, Monckhoven's intensifier
consisting of a mercuric salt bleach followed by a silver nitrate/potassium
cyanide solution, mercuric iodide/sodium sulfite, and uranium nitrate
are older, now discarded, intensifiers.
Reduction of negatives is usually done with Farmer's
reducer, consisting of potassium ferricyanide and hypo. Reduction has also be done historically with
iodine/potassium cyanide, ammonium persulfate, and potassium permanganate/sulfuric
acid.
Hazards
- Potassium dichromate and potassium chlorochromate are probable
human carcinogens, and can cause skin allergies and ulceration. Potassium
chlorochromate can release highly toxic chlorine gas if heated or
if
acid is added.
- Concentrated hydrochloric acid is corrosive; the diluted acid
is a skin and eye irritant.
- Mercury compounds are moderately toxic by skin contact and may
be absorbed through the skin. They
are also highly toxic by inhalation and extremely toxic by ingestion.
Uranium intensifiers are radioactive, and are especially
hazardous to the kidneys.
- Sodium or potassium cyanide is extremely toxic by inhalation and
ingestion, and moderately toxic by skin contact.
Adding acid to cyanide forms extremely toxic hydrogen
cyanide gas which can be rapidly fatal.
- Potassium ferricyanide, although only slightly toxic by itself,
will release hydrogen cyanide gas if heated, if hot acid is added,
or if
exposed to strong ultraviolet light (e.g., carbon arcs).
Cases of cyanide poisoning have occurred through treating
Farmer's reducer with acid.
- Potassium permanganate and ammonium persulfate are strong oxidizers
and may cause fires or explosions in contact with solvents and other
organic materials.
Precautions
- Chromium intensifiers are probably the least toxic
intensifiers, even though they are probable human carcinogens.
Gloves and goggles should be worn when preparing and using these
intensifiers. Mix the powders in a glove box or wear a NIOSH-approved
toxic dust respirator. Do not
expose potassium chlorochromate to acid or heat.
- Do not use mercury, cyanide or uranium intensifiers,
or cyanide reducers because of their high or extreme toxicity.
- The safest reducer to use is Farmer's reducer.
Do not expose Farmer's reducer to acid, ultraviolet light,
or heat.
Toning a print usually involves replacement of silver
by another metal, for example, gold, selenium, uranium, platinum, or iron. In some cases, the toning involves replacement
of silver metal by brown silver sulfide, for example, in the various types
of sulfide toners. A variety of
other chemicals are also used in the toning solutions.
Hazards
- Sulfides release highly toxic hydrogen sulfide gas during toning,
or when treated with acid.
- Selenium is a skin and eye irritant and can cause kidney damage. Treatment of selenium salts with acid may
release highly toxic hydrogen selenide gas.
Selenium toners also give off large amounts of sulfur
dioxide gas.
- Gold and platinum salts are strong sensitizers and can produce
allergic skin reactions and asthma, particularly in fair-haired
people.
- Thiourea is a probable human carcinogen since it causes cancer
in animals.
Precautions
- Carry out normal precautions for handling toxic
chemicals as described in previous sections.
In particular, wear gloves and goggles.
See also the section on mixing photochemicals.
- Toning solutions must be used with local exhaust ventilation.
- Take precautions to make sure that sulfide or selenium
toners are not contaminated with acids.
For example, with two bath sulfide toners, make sure you rinse
the print well after bleaching in acid solution before dipping
it in
the sulfide developer.
- Avoid thiourea whenever possible because of its probable
cancer status.
Other Hazards (top)
Many other chemicals are also used in black and white
processing, including formaldehyde as a pre-hardener, a variety of oxidizing
agents as hypo eliminators (e.g., hydrogen peroxide and ammonia, potassium
permanganate, bleaches, and potassium persulfate), sodium sulfide to test
for residual silver, silver nitrate to test for residual hypo, solvents
such as methyl chloroform and freons for film and print cleaning, and
concentrated acids to clean trays.
Electrical outlets and equipment can present electrical
hazards in darkrooms due to the risk of splashing water.
Hazards
- Concentrated sulfuric acid, mixed with potassium permanganate
or potassium dichromate, produces highly corrosive permanganic and
chromic
acids.
- Hypochlorite bleaches can release highly toxic chlorine gas when
acid is added, or if heated.
- Potassium persulfate and other oxidizing agents used as hypo eliminators
may cause fires when in contact with easily oxidizable materials,
such
as many solvents and other combustible materials.
Most are also skin and eye irritants.
Precautions
- See previous sections for precautions in handling photographic
chemicals.
- Cleaning acids should be handled with great care.
Wear gloves, goggles and acid-proof, protective apron. Always add acid to the water when diluting.
- Do not add acid to, or heat, hypochlorite bleaches.
- Keep potassium persulfate and other strong oxidizing agents separate
from flammable and easily oxidizable substances.
- Install ground fault interrupters (GFCIs) whenever electrical
outlets or electrical equipment (e.g. enlargers) are within six feet
of the
risk of water splashes.
Color Processing (top)
Color processing is much more complicated than black
and white processing, and there is a wide variation in processes used
by different companies. Color
processing can be either done in trays or in automatic processors.
Developing Baths (top)
The first developer of color transparency processing
usually contains monomethyl-p-aminophenol sulfate, hydroquinone, and other
normal black and white developer components.
Color developers contain a wide variety of chemicals including
color coupling agents, penetrating solvents (such as benzyl alcohol, ethylene
glycol, and ethoxydiglycol), amines, and others.
Hazards
- See the developing section of black and white processing for
the hazards of standard black and white developers.
- In general, color developers are more hazardous than black and
white developers. Para-phenylene
diamine, and its dimethyl and diethyl derivatives, are known to
be highly toxic
by skin contact and absorption, inhalation, and ingestion. They can cause very severe skin irritation,
allergies and poisoning. Color
developers have also been linked to lichen planus, an inflammatory
skin
disease characterized by reddish pimples which can spread to
form rough scaly patches. Recent
color developing agents such as 4-amino-N-ethyl-N-[P-methane-
sulfonamidoethyl]-m-toluidine
sesquisulfate monohydrate and 4-amino-3-methyl-N-ethyl-N-[,3-hydroxyethyl]-aniline
sulfate are supposedly less hazardous, but still can cause skin
irritation
and allergies.
- Most amines, including ethylene diamine, tertiary-butylamine
borane, the various ethanolamines, etc. are strong sensitizers,
as well as skin
and respiratory irritants.
- Although many of the solvents are not very volatile at room
temperature, the elevated temperatures used in color processing
can increase the
amount of solvent vapors in the air.
The solvents are usually skin and eye irritants.
Precautions
- Wear gloves and goggles when handling color developers. Wash gloves with an acid-type hand cleaner (e.g. pHisoderm (R)),
and then water before removing them.
- Mix powders in a glove box, or wear a NIOSH-approved toxic dust
respirator.
- Color processing needs more ventilation
than black and white processing due to the use of solvents and
other toxic components at elevated temperatures.
Bleaching, Fixing, and Other Steps (top)
Many of the chemicals used in other steps of color processing
are essentially the same as those used for black and white processing.
Examples include the stop bath and fixing bath.
Bleaching uses a number of chemicals, including potassium ferricyanide,
potassium bromide, ammonium thiocyanate, and acids. Chemicals found in
prehardeners and stabilizers include succinaldehyde and formaldehyde;
neutralizers can contain hydroxylamine sulfate, acetic acid, and other
acids.
Hazards
- Formaldehyde is moderately toxic by skin contact, and highly toxic
by inhalation and ingestion. It
is an skin, eye and respiratory irritant, and strong sensitizer, and
is a probable human carcinogen. Formaldehyde
solutions contain some methanol, which is highly toxic by ingestion.
- Succinaldehyde is similar in toxicity to formaldehyde, but is
not a strong sensitizer or carcinogen.
- Hydroxylamine sulfate is a suspected teratogen in humans since
it is a teratogen (causes birth defects) in animals.
It is also a skin and eye irritant.
- Concentrated acids, such as glacial acetic acid, hydrobromic
acid, sulfamic acid and p-toluenesulfonic acids are corrosive by
skin contact,
inhalation and ingestion.
- Acid solutions, if they contain sulfites or bisulfites (e.g.,
neutralizing solutions), can release sulfur dioxide upon standing. If acid is carried over on the negative or transparency from one
step to another step containing sulfites or bisulfites, then sulfur
dioxide can be formed.
- Potassium ferricyanide will release hydrogen cyanide gas if
heated, if hot acid is added, or if exposed to strong ultraviolet
radiation.
Precautions
- Local exhaust ventilation is required for mixing of chemicals
and color processing.
- Use premixed solutions whenever possible.
- Avoid color processes using formaldehyde, if possible.
- Wear gloves, goggles and protective apron when mixing and handling
color processing chemicals. When
diluting solutions containing concentrated acids, always add the
acid
to the water. An eyewash should be available.
- A water rinse step is recommended between acid bleach steps
and fixing steps to reduce the production of sulfur dioxide gas.
- Do not add acid to solutions containing potassium ferricyanide
or thiocyanate salts.
- Control the temperature carefully according
to manufacturer's recommendations to reduce emissions of toxic
gases and vapors.
Disposal of Photochemicals (top)
There is considerable concern about the effect of dumping photographic
chemicals and solutions down the drain. The following recommendations are for disposing small volumes of
photographic solutions daily.
- Old or unused concentrated photographic chemical solutions, toning
solutions, ferricyanide solutions, chromium solutions, color processing
solutions containing high concentrations of solvents, and non-silver
solutions should be treated as hazardous waste
- Alkaline developer solutions should be neutralized first before
being poured down the drain. This
can be done with the stop bath or citric acid, using pH paper to
tell
when the solution has been neutralized (pH 7).
- Stop bath left over from neutralization of developer can be poured
down the drain, once mixed with wash water.
- Fixing baths should never be treated with acid (e.g mixing with
stop bath), since they usually contain sulfites and bisulfites which
will
produce sulfur dioxide gas.
- Fixing baths contain large concentrations of silver thiocyanate,
well above the 5 ppm of silver ion allowed by the U.S. Clean Water
Act. Collect fixers and either pour into the silver recovery unit or
dispose as hazardous waste.
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