collection care: environmental factors
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Collection Care:Environmental Factors
Valinda S. Carroll
Agents of Deterioration
High Temperature
Humidity Light Pests and Fungi Handling Air Pollution
Temperature and Humidity
Traditionally, museum climate control has been based on human comfort, the capacity of the heating and air conditioning system, and the limitations of the building.
High Temperature
High temperatures may damage artifacts in several ways
Causes cross-linking (makes materials become brittle)
Causes chain scission (makes materials weaker)
Makes materials expand (causes splitting and delamination)
Lowers relative humidity (causes shrinkage and splitting)
High Humidity
Excessive humidity is damaging to art and historic artifacts
Accelerates chemical damage
Promotes swelling, distortions, and delamination
Encourages mold growth Increases insect activity
(especially combined with high temperature)
Warped floor tiles
Measurement Tools
Handheld Thermohygrometer
Thermometer and Psychrometer
Recording Hygrothermograph
Electronic Data loggers Temperature and
Humidity Indicator Cards
Advantages
• Displays relative humidity• Displays temperature• Portable• Easy to use• Does not require
additional equipment or supplies
• Inexpensive
HandheldThermohygrometer
Disadvantages
• Does not record over time
• Does not store readings
• May be inaccurate, and difficult to calibrate
• User must purchase batteries
HandheldThermohygrometer
Aspirating Psychrometer
• Compares wet bulb and dry bulb temperature to find dew point and relative humidity
• Contains light to make thermometers easier to read
Aspirating Psychrometer
Uses a fan to evaporate moisture from cloth on wet bulb
Can assist in calibrating other instruments
More reliable and easier to use than sling psychrometer
Wet bulb
Aspirating Psychrometer
• Does not record over time
• Requires slide rule or mathematical calculations
• Does not generate documentation
Recording Hygrothermograph
Recording hygrothermographAdvantages
• Shows temperature
Red temperature line
Recording hygrothermographAdvantages
• Shows temperature• Shows humidity
Blue humidity line
Data logger
Advantages Records over time Small enough to fit into
exhibit case or packing crate
Data can be loaded into standard spreadsheet software to generate reports
May be less expensive than hygrothermograph
Data logger
Requires batteries Inexpensive models
cannot be read without computer
Inexpensive models must be downloaded individually, by hand
Disadvantages
Advantages
• Small enough to fit into frame, exhibit case, or shipping crate
• Inexpensive unit cost
• Does not require batteries
• Does not require computer or slide rule
Humidity Card
Disadvantages
• Imprecise
• Not durable
• Does not record over time
• Cobalt blue salt is toxic (orange humidity cards are non-toxic)
Humidity Card
Advantages
• Inexpensive
• Easy to use
• Portable
• Small enough to fit into frame, exhibit case, or shipping crate
Temperature Card
Disadvantages
Temperature Card
• Imprecise
• Does not record over time
• Does not generate permanent documentation
• Not durable
Effects of Light
Light is necessary for exhibits, but excess exposure can lead to many problems
Fading
Yellowing
Weakening and breakage of fibers and polymers
Light Monitoring Tools
Blue Wool standard
Light meter
UV meter
Light data logger
Blue woolAdvantages• Blue wool swatches provide a qualitative
assessment of fading.
• They are compact and portable enough to use in frames or exhibit cases.
• A spectrophotometer or colorimeter may be used to detect blue dye fading before it becomes visible to the human eye.
Blue woolDisadvantages
• Blue wool standard swatches only show fading; they cannot indicate future fading or other types of damage.
• The extent and rate of fading vary depending on the spectrum of the light source. Blue wool standards were designed for use with sunlight, not artificial lights.
Light MeterAdvantages•Can measure output from windows and lamps•Can measure incident light falling on surface of object•Portable•Can be read instantly•Can show lux or foot-candles (1 foot-candle~ 10 lux)
Light MeterDisadvantages•Does not generate permanent record•Requires batteries
Ultraviolet radiation is expressed relative to the overall light level in lux. The maximum recommended amount of UV is 0.375 microwatts per square centimeter, measured at a light level of 50 lux (about 5 foot-candles).
Ultraviolet Meter
Ultraviolet (UV) meter showing 9 microwatts per square centimeter, a rather high level.
UV-filtering materials
Ultraviolet filtering materials can be used in windows, light fixtures, exhibit cases, and/or frames
• Acrylic (Plexiglas UF, Acrylite OP, TrueVue Optium)
• Polycarbonate (Lexan)• Laminated Glass (Schott
Amiran)• Filtering window films• Fluorescent tube sleeves
Mitigation Strategies
Store collections in closed boxes and cabinets, rather than open shelves
Close shutters (in historic buildings), shades, or blinds
Use UV-filtering glazing in frames and exhibit cases and UV-filtering sleeves on lights
Hang curtains in front of vulnerable artwork or drape cloth over exhibit cases when museum is closed
Use motion detector switches for gallery lighting
Mold Safety Always wear personal protective
equipment: N95 respirator, gloves, goggles
Use a HEPA vacuum and a soft brush ( a HEPA or ULPA filter prevents the vacuum cleaner from filling the air with microscopic mold spores)
Create a work area separate from collections storage to avoid cross-contamination
Insects
Many insects are attracted to food eaten by humans
Insects seek shelter in human habitations, especially during inclement weather
Many insects feed on starches and proteins in museum artifacts
Some insects eat only one type of material, so it is useful to consult an identification chart
Rodents
Rodents are attracted to food eaten by humans
Rodents seek shelter in human habitations, especially during inclement weather
Rodents feed on starches and proteins in museum artifacts
Pest Control Methods
Seal entry points (caulk, weather-strip, etc.)
Remove food sources and breeding places
Use outdoor bait stations to control rodents before they enter the building
Monitor insect activity with sticky traps and pheromone lures
Pest Control Methods
Lower temperatures, possibly to freezing point
Reduce relative humidity Remove sources of oxygen
(nitrogen or argon chamber, Ageless™ oxygen absorber)
Air Pollutants
Soot and smoke Outdoor pollutants Volatile organic compounds Off-gassing from collections and exhibit
materials Ozone
Open Flames
Use electric or battery-operated candles and fireplace inserts to avoid unnecessary risks to your collection
• Candles generate soot
• Flames in generate very high heat
• Genuine candles, working fireplaces, and cigarette smoking may lead to fires
Outdoor Pollutants
Car exhaustFactoriesForest fires
Outdoor Pollutants
Keep windows and doors closed
Change filters in HVAC system
Store artifacts in protective enclosures
Volatile Organic Compounds
Regular Paint Low VOC Paint
Off-gassing
Protect artifacts from contact with materials known to release harmful gasses
Unstable plastics (cellulose acetate, cellulose nitrate, etc.)
Unsealed wood (interior grade plywood, oak, etc.)
Paints or cleaning materials of unknown or untested composition
Volatile acetic acid(cellulose acetate film deterioration)
Controls
slight
severe
severe
moderate
Oddy Test
Hidden dangers
Ozone
Photocopiers and laser printers emit ozone. Keep such machines in office spaces separate from from collections storage areas.
Protective Housing Materials
Absorb or adsorb chemical pollutants from the air
Thin sheets can be incorporated into frames and exhibit cases
May act as mechanical barriers to pollutants
Easy to usePlastic films and bags with Intercept ™ technology (finely divided copper)
Protective Housing Materials
Microchamber ™ paper Bainbridge Alpharag
Artcare ™ Scavengel ™ cloth Activated charcoal
cloth Corrosion Intercept ™
films and bags (plastic impregnated with finely divided copper)
Protective Housing Materials
Activated charcoal and potassium permanganate
sheets
Zeolite-containing alkaline rag board
Protective Housing Materials
Capacity to counteract pollutants not easily determined
Shelf life not easily determined
More expensive than traditional housing materials
END
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