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Arts Safety – Color Photo Processing

Color processing is much more complicated than black-and-white processing, and there is a wide variation in processes used. Color processing can be either done in trays or in automatic processors. Color Developing Baths 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 various chemicals including color coupling agents, penetrating solvents (such as benzyl alcohol, ethylene glycol, and ethoxydiglycol), amines, and others.

Things to Consider

Hazards

  1. See the developing section of black-and-white processing for the hazards of standard black-and-white developers.
  2. In general, color developers are more hazardous than black and white developers. Paraphenylene diamine, and its dimethyl and diethyl derivatives, are known to be toxic by skin contact and absorption, inhalation, and ingestion. Recent color-developing agents such as 4-amino-Nethyl-N-[P-methane- sulfonamido ethyl]-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.
  3. Most amines, including ethylene diamine, tertiary-butylamine borane, the various ethanolamines, etc. are strong sensitizers, as well as skin and respiratory irritants.
  4. 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.

Precautions

  1. Wear gloves and goggles when handling color developers. Wash gloves with soap and water before removing them.
  2. Mix powders in a glove box, or with local exhaust ventilation (fume hood).
  3. Color processing needs more ventilation than black-and-white processing due to the use of solvents and other components at elevated temperatures.

 

Color Processing

Bleaching, Fixing, and Other Steps 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
  1. Formaldehyde is toxic by skin contact, inhalation and ingestion. It is a skin, eye and respiratory irritant, and strong sensitizer, and is a probable human carcinogen. Use of formaldehyde requires an exposure assessment by EHS. Contact EHS to schedule.
  2. Succinaldehyde is similar in toxicity to formaldehyde, but is not a sensitizer or carcinogen.
  3. Hydroxylamine sulfate is a suspected teratogen in humans. It is also a skin and eye irritant.
  4. Concentrated acids, such as glacial acetic acid, hydrobromic acid, sulfamic acid and ptoluenesulfonic acids are corrosive by skin contact, inhalation and ingestion.
  5. 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.
  6. Potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet radiation.
Precautions
  1. Local exhaust ventilation is required for mixing of chemicals and color processing.
  2. Use premixed solutions whenever possible.
  3. Avoid color processes using formaldehyde, if possible.
  4. 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.
  5. A water rinse step is recommended between acid bleach steps and fixing steps to reduce the production of sulfur dioxide gas.
  6. Do not add acid to solutions containing potassium ferricyanide or thiocyanate salts.
  7. Control the temperature carefully according to the manufacturer’s recommendations to reduce emissions of toxic gases and vapors.

 

Disposal of Photo chemicals

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.

  1. 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 and disposed by EHS.
  2. 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.
  3. 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 them into a silver recovery unit or dispose as hazardous waste.

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