Collection Care II: Temperature and Humidity
Download as pptx, pdf2 likes1,413 views
The document discusses various tools for monitoring environmental conditions like temperature and humidity that can damage collections, including hygrometers, psychrometers, data loggers, and indicator cards. It explains that temperature and humidity should be monitored together, as temperature affects relative humidity levels. The ideal storage conditions for most collections is a relative humidity between 35-55% along with moderate temperature fluctuations to avoid damage from fluctuations or high levels.
Collection Care II: Temperature and Humidity
- 1. Collection Care: Environmental Factors Part I: Temperature and Humidity Valinda S. Carroll
- 2. Agents of Deterioration High Temperature Humidity Light Pests and Fungi Handling Air Pollution
- 3. Environmental Monitoring Determine current conditions for storage and exhibition, before investing in conservation treatment. It would be a poor investment to conserve an artifact, only to return it to a damaging exhibit gallery or storage space. A monitoring program allows an institution to set preservation priorities according the specific needs of its collection.
- 4. 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.
- 5. Temperature and Humidity Since 1994, published research has measured damage induced by climate fluctuations. In some instances, this research has resulted in wider acceptable climate ranges, adjusted for local conditions. Collections housed in historic buildings may be required to tolerate slight seasonal climate fluctuations in order to preserve the buildings.
- 6. High Temperature High temperatures may Causes cross-linking damage artifacts in (makes materials become several ways brittle) Causes chain scission (makes materials weaker) Makes materials expand (causes splitting and delamination) Lowers relative humidity (causes shrinkage and splitting)
- 7. Temperature and Humidity Relative humidity is directly affected by temperature, so the two factors should be monitored together. An increase in temperature results in a decrease in relative humidity, because warm air has the capacity to hold more water. As the temperature is reduced, relative humidity increases until it reaches 100%, and water condenses on surfaces. This temperature is called the dew point. Dehumidification is important to avoid condensation. A relative humidity range of 35% to 55% is safe for most types of collections, and allows moderate temperature variations.
- 8. High Humidity Excessive humidity is Accelerates chemical damaging to art and damage historic artifacts Promotes swelling, distortions, and delamination Encourages mold growth Increases insect activity (especially combined with high temperature) Warped floor tiles
- 9. Measurement Tools Handheld Recording Thermohygrometer Hygrothermograph Thermometer and Electronic Data loggers Psychrometer Temperature and Humidity Indicator Cards
- 10. Handheld Thermohygrometer Advantages Displays relative humidity Displays temperature Portable Easy to use Does not require additional equipment or supplies Inexpensive
- 11. Handheld Thermohygrometer Disadvantages Does not record over time Does not store readings May be inaccurate, and difficult to calibrate User must purchase batteries
- 12. Aspirating Psychrometer Compares wet bulb and dry bulb temperature to find dew point and relative humidity Contains light to make thermometers easier to read
- 13. Aspirating Psychrometer Uses a fan to evaporate moisture from cloth on wet bulb Can assist in calibrating Wet bulb other instruments More reliable and easier to use than sling psychrometer
- 14. Aspirating Psychrometer Does not record over time Requires slide rule or mathematical calculations Does not generate documentation
- 15. Temperature and humidity guidelines from the psychrometer manual: The temperature range of 70-80F degrees for libraries and museums on this chart is aimed at human comfort rather than collection care.
- 17. Recording hygrothermograph Advantages Shows temperature Red temperature line
- 18. Recording hygrothermograph Advantages Shows temperature Shows humidity Blue humidity line
- 19. Recording hygrothermograph Advantages Shows temperature Shows humidity Records over time: daily, monthly, or weekly User may calibrate to improve accuracy Some types run without batteries or Toggle switch for 1 day, electricity (wind-up clockwork 7 days, or 32 days mechanism) Easy to use Paper chart provides long-term record for comparison over seasons or years Continues to work during staff vacations or even during disasters
- 20. Recording hygrothermograph Disadvantages May require regular winding or battery replacement User must purchase paper charts and replacement pens Expensive Paper charts require storage space Red and blue ink lines may be faint and difficult to see Cannot shift between Fahrenheit and Celsius, nor show dew point, etc. Cannot be included in computer-generated reports and presentations
- 21. 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
- 22. Data logger Disadvantages Requires batteries Inexpensive models cannot be read without computer Inexpensive models must be downloaded individually, by hand
- 23. Humidity Card 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
- 24. Humidity Card Disadvantages Imprecise Not durable Does not record over time Cobalt blue salt is toxic (orange humidity cards are non-toxic)
- 25. Temperature Card Advantages Inexpensive Easy to use Portable Small enough to fit into frame, exhibit case, or shipping crate
- 26. Temperature Card Disadvantages Imprecise Does not record over time Does not generate permanent documentation Not durable
- 27. End of Section Please proceed to Part II: Light