Surrey Museums Partnership Conservation Seminars continued on 7th April with an informative, in-depth look into the world of data-loggers and software given by Michael Hall and Samantha Greatbatch from Meaco Measurement and Control Ltd.
They brought us up to date with the latest developments in environmental equipment, explained the levels of accuracy that are now achievable and the importance of annual calibration. They stressed that while the eminently affordable min/max digital devices have their uses, they cannot provide reliable, downloadable annual data which is crucial to understanding the museum environment.
There is equipment for every museum situation:
- Wireless telemetric systems transmit data from remote loggers, directly to the computer. They provide live as well as recorded data and will send warning emails if alarms are triggered by unexpected peaks! These systems are independent of Building Management Systems, providing an additional stop-check should anything go awry.
- Tinytag data-loggers. A very user friendly logger which holds up to 5 months of data at the recommended 15 minute recording intervals. They are accurate to +- 3% RH +- 0.3C. The software is easy to use as it shows the data in a graphical and tabular format; the data can also be exported into an Excel spreadsheet or as an image of a graph into a word document. Min/max and average readings are available and LED displays on the front of the logger flash if the battery is low or there has been an unexpected peak. The Tinytag [ at least the most affordable option] has no digital screen, difficult to source batteries and the software is not free.
- Rotronic 1D data-loggers are comparable to the Tinytag in terms of accuracy and reliability though have a digital screen for spot readings, easily sourced batteries and free software. If stopped and started without downloading the existing data will be saved [ not the case with Tinytag]. The software highlights battery life but is less user friendly than the Tinytag equivalent.
As with all environmental equipment, the data produced is only relevant if the machines are calibrated annually. Meaco offer a calibration service or, if feeling confident, calibration can be undertaken in-house with a handheld reference device and calibration chamber and salts.
Michael and Samantha recommend downloading regularly to really grasp environmental conditions. Simple procedures, such as making people leave wet umbrellas and coats in a cupboard or at the entrance, could remove an unpleasant rise in RH levels. Remember stability is all important.
In September 2014 the IIC [International Institute for Conservation of Historic and Artistic Works] issued the Bizot Interim Guidelines for Hygroscopic Materials:
- For many classes of object[s] containing hygroscopic material (such as canvas paintings, textiles, ethnographic objects or animal glue) a stable relative humidity (RH) is required in the range of 40–60% and a stable temperature in the range 16–25°C with fluctuations of no more than ±10% RH per 24 hours within this range.
More sensitive objects will require specific and tighter RH control, depending on the materials, condition, and history of the work of art. A conservator’s evaluation is essential in establishing the appropriate environmental conditions for works of art requested for loan.