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What is Collection’s Care?
How Can Museum Objects Deteriorate?
There are numerous factors influencing deterioration of museum objects.
- All objects are subject to decay caused by physical, biological and chemical changes.
- Different materials deteriorate at different rates and in different ways depending on factors such as environmental conditions.
- The rate of decay depends on what the object is made of; is it a delicate cotton textile or a medieval stone fragment?
How Do We Reduce Deterioration?
The museum strives to control the factors that promote the deterioration of museum objects. These are as follows:
- Temperature (T) and Relative Humidity (RH).
- Light both visible and invisible such as UV-light.
- Air pollutants i.e. gasses and dust
- Pests i.e. moulds, insects and rodents
The following is a sample of the measures in place to reduce the risk of deterioration of objects in the museum collection.
Environmental Monitoring / Control
Temperature and Relative Humidity is measured using Hanwell Radiolog System. A total of twenty ml-400 RH/T sensors are placed around the museum, including showcases and collection rooms. These sensors send a signal to the base station located on the ground floor. The base station sends the signal to the Museum Technician’s computer located on the second floor. The data is displayed in graph form. The frequency of readings are set at five second intervals. This data can also be downloaded as raw numerical data in the form of a CSV file which can be incorporated into thermal modelling software.
RH/T spot checks are carried out using the handheld ULM. (RH/T option)
The BMS also records temperature in the building. This data is cross referenced with the hanwell system. Currently the BMS data logger controls each air handling unit, radiators, and under floor heating.
The following is a sample from the environmental monitoring system:
Three CCR 30 RH control units control RH at the museum. The unit combine a humidifier and dehumidifier in order to create a stable environment. The CCR30 works by conditioning the air based on the data it receives from the ml-400 RH/T sensor.
Further control is achieved through the combined use of hermetically sealed showcases and silica gel.
As the museum is constructed using a high percentage of glazing, solar gain must be minimised. This is achieved through the use of three types of solar films applied to the glazing. The following is the performance data on each film.
Light is monitored through the use of four Hanwell LUX/UV dataloggers and a hand held ULM. Light is controlled using various methods such as the use of black out blinds, and the construction of walls to cover the existing glazing.
Air pollutants are controlled through the use of an air bag filtration system. These filters are attached to the air handling units.
All pollutants from human contact are eliminated through the use of acid free cotton gloves.
Galway City Museum implements a detailed pest management policy. The following is a sample of the procedures in place for dealing with museum pests.
Currently the museum uses “AgriScience” sticky traps. These are placed a various location throughout the building. Traps are checked on a weekly basis and appropriate documentation is completed. Traps are replaced every two months.
A condition report is completed for all newly acquired material. As part of this condition assessment, the object is checked for evidence of pests. When appropriate, the museum checks objects before they enter the building. When this cannot be achieved, the object is wrapped in polyethylene and placed in the quarantine area for inspection. Inspection is immediate. The museum has two methods of dealing with pest detection. They are as follows:
- Oxygen Scavenging
The appropriate object is placed in a polyethylene bag and all air is removed. The bag is heat sealed and placed in the freezer for 24 – to 48 hours. The temperature is set a below 44 degrees C. When removed, the object is allowed to acclimatize for at least 24 hours before opening. A detailed examination of the object is preformed in order to ensure the treatment has been successful.
As the freezing method is not suitable for some material types, such as paper, and paintings, oxygen scavenging treatment is compatible with a high percentage of the museum collection, although the treatment time required is much longer.
The object is placed in marvel seal bag with the oxygen scavengers. The bag is then heat sealed and placed on the shelving system in the quarantine room. The object is removed after thirty days and assessed for the presence of pests. All pest carcasses are removed. The condition report is then updated.
For further information on collections care please contact James Reynolds, Museum Technician.
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