Collection Care:Environmental Factors Valinda S. Carroll
Agents of Deterioration High Temperature Humidity Light Pests and Fungi Handling Air Pollution
Temperature and HumidityTraditionally, museum climate controlhas been based on human comfort, thecapacity of the heating and airconditioning system, and the limitationsof the building.
High TemperatureHigh temperatures may Causes cross-linkingdamage artifacts in (makes materials becomeseveral ways brittle) Causes chain scission (makes materials weaker) Makes materials expand (causes splitting and delamination) Lowers relative humidity (causes shrinkage and splitting)
High HumidityExcessive humidity is Accelerates chemicaldamaging to art and damagehistoric artifacts Promotes swelling, distortions, and delamination Encourages mold growth Increases insect activity (especially combined with high temperature) Warped floor tiles
Measurement Tools Handheld Recording Thermohygrometer Hygrothermograph Thermometer and Electronic Data loggers Psychrometer Temperature and Humidity Indicator Cards
Handheld ThermohygrometerAdvantages•Displays relative humidity•Displays temperature•Portable•Easy to use•Does not require additionalequipment or supplies•Inexpensive
Handheld ThermohygrometerDisadvantages•Does not record overtime•Does not store readings•May be inaccurate, anddifficult to calibrate•User must purchasebatteries
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 calibratingWet bulb other instruments More reliable and easier to use than sling psychrometer
Aspirating Psychrometer • Does not record over time • Requires slide rule or mathematical calculations • Does not generate documentation
Data loggerAdvantages 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 loggerDisadvantages Requires batteries Inexpensive models cannot be read without computer Inexpensive models must be downloaded individually, by hand
Humidity CardAdvantages • 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 CardDisadvantages • Imprecise •Not durable •Does not record over time •Cobalt blue salt is toxic (orange humidity cards are non-toxic)
Temperature CardAdvantages•Inexpensive•Easy to use•Portable•Small enough to fit into frame,exhibit case, or shipping crate
Temperature CardDisadvantages•Imprecise•Does not record over time•Does not generate permanentdocumentation•Not durable
Effects of LightLight 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 qualitativeassessment of fading.•They are compact and portable enough to use inframes or exhibit cases.•A spectrophotometer or colorimeter may be usedto detect blue dye fading before it becomes visibleto the human eye.
Blue woolDisadvantages•Blue wool standard swatches only showfading; they cannot indicate future fading orother types of damage.•The extent and rate of fading vary dependingon the spectrum of the light source. Blue woolstandards were designed for use with sunlight,not artificial lights.
Light MeterAdvantages•Can measure output fromwindows and lamps•Can measure incidentlight falling on surface ofobject•Portable•Can be read instantly•Can show lux or foot-candles(1 foot-candle~ 10 lux)
Light MeterDisadvantages•Does not generatepermanent record•Requires batteries
Ultraviolet MeterUltraviolet radiation is expressed relative to the overall light level inlux. The maximum recommended amount of UV is 0.375microwatts per square centimeter, measured at a light level of 50lux (about 5 foot-candles). 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 Some insects eat only eaten by humans one type of material, so Insects seek shelter it is useful to consult an in human identification chart habitations, especially during inclement weather Many insects feed on starches and proteins in museum artifacts
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 •Candles generate soot •Flames in generate very high heat •Genuine candles, working fireplaces, and cigarette smoking may lead to firesUse electric or battery-operated candles and fireplace inserts to avoid unnecessary risks to your collection
Hidden dangers Ozone Photocopiers and laserprinters emit ozone. Keepsuch machines in officespaces separate fromfrom collections storageareas.
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 Plastic films and bags with Easy to use 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)