Film conservation hazards

Introduction
Biological hazards
Chemical hazards
Decomposition and off-gassed products
Chemicals used in conservation treatments
Identifying chemical hazards

Introduction

There are several hazards that arise in the treatments used for the conservation of archival motion picture film. Chemical and biological hazards need to be recognised and controlled so that the operations can be carried out with minimal risk to staff. The lynch pin of safety around archival films is careful attention to hygiene.

Biological hazards

Gelatin is an excellent food source for a variety of life forms. Apart from any bacteria that may be found on the film itself there are many vermin that use the film as a food source that may also spread disease unless good hygiene is observed while handling film collections.

Moulds are the primary hazard that needs to be considered. Mould spores are present in large numbers in most environments. Whether there are appreciably more spores present around film is debatable, however due to this unknown mouldy films should be treated with care.

The precise effects that moulds found on film may have on people is relatively unknown. However it is generally assumed that respiratory problems would be the most likely, with eye infections and skin disorders also a possibility.

Mouldy films should be handled in a fume cupboard or other approved extraction system. Disposable examination gloves should be worn and after use the gloves turned inside out and disposed of. Washing hands after handling any archival film, regardless of any obvious signs of infestation, is highly recommended.

Chemical hazards

Exposure to chemicals when treating archival films come from two sources:

  • Chemicals used in the treatment, these are of a known purity and quantity and have health and safety data available
  • Decomposition by products, these are an unknown in terms of purity and quantity and have scant information available.

There are five major classes of chemical hazard – toxics, flammables, reactives, corrosives and pollutants.

Toxics

Toxic chemicals affect the body by destroying cells and tissues, changing enzyme functions and interfering with the operation of the bodies systems such as the nervous system, cardiovascular system, respiratory system, major organs, genetic material or immune system.
The chemical can enter the body by a number of routes.

  • Inhalation – chemicals are breathed in and enter the body via absorption along the airways and lungs. This presents the greatest risk to worker safety.
  • Skin absorption – generally the skin is well protected by an oily film that helps keep the skin supple and protects the skin from water and water soluble (hydrophilic) chemicals. Some chemicals, particularly those that can dissolve or remove the protective layer (called defatting) cause irritation or permit other chemicals to be more readily absorbed.
  • Ingestion this is an obvious route of entry but the effects of the chemical depend on the absorption of the chemical by the gastro intestinal tract and internal transport through the bloodstream.

Flammables

Most chemicals will burn if sufficient heat is applied. Many chemicals will combust at very low temperatures and will create a significant fire hazard under normal temperature conditions.

The assessment of the flammability of a chemical is determined by its flash point(fp). The flash point is the minimum temperature at which there will be sufficient vapour from the chemicals surface to ignite when an ignition source is present.

Description Flash Point (fp)
Flammable between 23-61°C
Highly Flammable between 0-22°C
Extremely Flammable less than 0°C

Some chemicals are not only flammable but also very difficult to suppress once alight. Cellulose nitrate film is one such chemical. The structure of the film contains chemicals that will support combustion without air. Smothering or water sprays are generally insufficient to extinguish nitrate film once it is alight, nitrate film has even been recorded as continuing to burn after it has been placed under water!

Reactives

Some chemicals will combine readily with other chemicals, water or even air, to create a dangerous situation. This might cause a fire, toxic gases or even an explosion depending on the quantity and reactivity of the chemicals involved.

Consideration of a chemicals reactivity should be given not only for its use but also for storage and transport. Even carrying incompatible chemicals from a store to where they are to be used creates a risk that needs to be properly managed.

Corrosives

Corrosive chemicals are acids and alkalis (or bases) which can cause burns on contact with the skin. Again this is a consideration for use, storage and transporting.

Pollutants

These create an environmental hazard. The hazard may be one of toxicity, a high oxygen demand in sewerage and waterways, ozone depletion, soil poisoning or another long term problem.

Decomposition and off-gassed products

In a survey of a black and white film vault, the Image Permanence Institute identified the following chemicals in detectable quantities:

1-butanol hexane toluene
carbon disulfide methylene chloride xylene
cyclohexane pentane
cyclopentane iso-pentane
1,2-dichloropropane perchloroethylene
Freon TF trichlorofluoromethane

Table 9.1 Decomposition and off-gassed products

Many of these would be residual casting solvents, cleaning solvents and decomposition products from plasticisers.

In dealing with decomposing films the main decomposition products of concern are acids and plasticisers, including some of the plasticisers decomposition by-products:

Acetic Acid Nitric Acid Methylene chloride
Butyric acid Phosphoric Acid Triphenyl phosphate
Propionic Acid Diphenyl phosphate Phenol

Table 9.2 Decomposition by-products

Chemicals used in conservation treatments

The main chemicals used in treatments described in this resource are solvents and the salts used to prepare aqueous solutions. Listed below are the commonly used chemicals:

Solvents Salts
absolute ethanol (99.5%) sodium metabisulfite
3M HFE’s, 7100 & 71-DA sodium sulfite
d-limonene sodium tripolyphosphate
methanol
perchloroethylene

Table 9.3 Chemicals used in film conservation

Identifying chemical hazards

Information regarding the hazards posed by chemicals is obtained from Material Safety Data Sheets (MSDS). These sheets are a legal document and must contain certain information, including:

  • Product name
  • Other names
  • UN Number, Dangerous Goods Class and Subsidiary Risk
  • Hazchem Code
  • Poisons Schedule
  • Use
  • Physical description and properties
  • Health information
  • First Aid
  • Advice to doctors
  • Precautions for use
  • Exposure standards and controls, including protective equipment
  • Safe handling information, including spill procedures and disposal

Apart from the obvious biological and chemical hazards working with old film can present some physical hazards including minor (although possibly deep) cuts and abrasions from the edges of the film and scalpels, winding injuries, lifting injuries and eye strain.

Close attention to existing OH&S Policies is important, but beyond this extra care needs to be taken in laboratory cleanliness and personal hygiene.