CECILY GRZYWACZ

The Getty Conservation Institute

GCI POLLUTION RESEARCH : WHAT WE HAVE LEARNED AND WHERE DO WE GO FROM HERE ?

The Getty Conservation Institute has been involved in environment research since the mid 1980's.

1. Investigation of infiltration of outdoor pollutants was initiated and this continued through the early 1990's.
2. In 1987, we began investigating organic carbonyl pollutant concentrations in museum environments.
   - This was shortly after the Hatchfield and Carpenter study on formaldehyde levels.
   - We used active sampling to quantify the levels of aldehydes, specifically formaldehyde and acetaldehyde, low molecular weight carboxylic acids; formic acid and acetic acid.
3. Our findings indicated that organic carbonyl pollutants were not as prevalent in museum environments as feared. As logic would have it, the concentrations increased as the ventilation decreased.
   - Hence, typically galleries and storerooms have the lowest concentrations.
   - The highest concentrations were detected in show cases and storage cabinets.
4. A survey was undertaken in the UK and Amsterdam. Experiments were performed in areas with known damage, and high concentrations of acetic acid were observed. This pollutant is thought to be the most damaging of the organic carbonyl pollutants.
5. The technology is there to monitor formaldehyde,
   - But how readily does formaldehyde oxidise to formic acid and,
   - Do we detect relatively low concentrations of formic acid because it is so reactive ?
6. High molecular weight aldehydes and ketones have also been detected inside display cases, one was identified as a cyclohexanone. Has anyone else seen this ?

Currently, there is no formal pollution research program.
- The knowledge gained is implemented into new research projects.
- It is known that we cannot consider preservation without considering all environmental factors such as; temperature, light, relative humidity, pollutants and meteorological data for outdoor sites, etc.

When questions arise that we don't understand, it provides an opportunity to conduct more research, e.g., sustainable technologies in hot and humid climates. We will investigate the effectiveness of zeolites for pollutant mitigation. As well as the effect of increasing ventilation to decrease humidity and mould growth, will that increase the risk of damage from outdoor pollutants within museums ?

Do we need qualitative or quantitative data to measure the efficacy of mitigation strategies ?

Blindly investing time, energy and fiscal reserves into mitigation measures is a waste of precious resources.
- Initial test : determine if there is still a problem, what is the extent of the problem, what are the likely sources, and what is the best mitigation strategy ?
- Implement mitigation methodology
- Test again to determine how effective
- Observe again for continued damage
- Test again for long term effectiveness
- Observe regularly as in any preventive conservation protocol for a collection

Many instances when mitigation measures actually made it worse !

1. Replacing one type of wood cabinet for another, especially plywood for new wood.
2. Improperly cured baked enamel on steel cabinets.
3. Mixing of media of objects within cases or cabinets.
4. Exposure of fresh wood, or wood product surfaces.
5. Improper installation of sorbents
6. Improper sealing of wood products, both barrier foils and coatings.

What causes the damage ?....
        What should we monitor for ?

Detected on Objects:

• acetates and formates on surfaces and in corrosion products.
• chlorides: external sea salts, internal to the artefacts, or HCl
• sulfides: H₂S and / or COS
• sulfites: extreme situations
• ammonia seems to increase damage risk to metals (ref : D. Scott, GCI)

What about oxidation and breakdown of compounds...

• oxidation of formaldehyde to formic acid
• oxidation of acetaldehyde to acetic acid

Chemically both reactions are feasible, but is this the issue at hand ? In our labs, visible corrosion or changes to the surfaces of inorganic materials were observed after 100 d exposure to 1.2 ppm (1200 ppb) formaldehyde, T = 20°C, RH = 50 - 55 % (ref : M. Striegel, GCI)

What about higher molecular weight carbonyl compounds ?

• Do these degrade to lower molecular weight compounds which then damage artefacts?
• Especially significant if the high molecular weight compound breaks down to acetates or formates.

Passive sampling devices (PSDs)
- Direct reading, no laboratory analysis required would be great

• available for ozone - very economical, but usually want a suite of pollutants.
• Direct reading is subject to interference

• These are sensitive, typically pollutant specific, and simple to deploy and retrieve.
• Can be expensive, especially if a complete pollutant survey is required organic acids - £65 per site (both acetic and formic acid measurements given, three tubes provide mean results as well as replicate blank measurements)
  aldehydes - £25 per site (for 1 measurement only of formaldehyde and blank)
    - with acetaldehyde £42 total
    - with cyclohexanone £60 total
  hydrogen sulfide - £180 per site (replicate measurements taken)

Conclusion :
Damage to collections is a function of an object's composition, its history, pollutant type and concentration, time, relative humidity and temperature.
HIGH concentrations with susceptible objects and long exposure time : potentially an immediate problem
MODERATE concentrations and susceptibility of artefact : may be a problem depending on exposure time.
LOW concentration : assume that risk is low. Damage may occur, but it may be beyond our lifetimes.

ADDITIONAL NOTES

Pollutants have been known to lead to the complete destruction of artefacts. The effect is irreversible, thus there are no safe acceptable threshold levels.

Damage can be caused by a number of factors : Biological, pollution, RH, light, temperature, natural disasters, human ignorance and physical factors.

Testing materials : All materials should be tested before use. After construction, 'they say' you should typically let the building off-gas for 9 - 12 months. However, HVAC systems can clean the building galleries within an hour of tours coming through.

Note : Palliative measures do not always eliminate the problem. For example, medite is found to be formaldehyde free, but releases acetic acid and formic acid. Barrier foils significantly reduce pollutant levels, but do not eliminate them. There needs to be effective communication between the sorbent and the display cases. Even baked enamel on steel cabinets was deleterious to lead coupons which were destroyed after only 3 months. The formaldehyde concentration was found to be 3 ppm. These cabinets were not properly cured.

Conclusions:
Need to gather information on damage correlations
Understand the susceptibility of materials
Need to consider the levels at which damage occurs
Continue to analyse corrosion products
Understand the role of temperature and relative humidity
Remember that any improvement is valuable.