At the beginning of March this year Knole was visited by Nigel Blades, the Preventive Conservation Advisor for the National Trust and a team of researchers from the Polish Academy of Sciences in Krakow. They were here to install some pioneering technology in the world of heritage sciences. With the help of furniture conservator John Hartley they have attached acoustic emission (AE) monitors to some of the most important objects in the house. The basic principal of these sensors is to listen for otherwise imperceptible noises emanating from objects as they react to the changing environment around them.
Some of the sensors have been attached simply by wedging plastazote (an inert spongy material) into a convenient crevice, whereas others required gluing by a furniture conservator (although a hairdryer was needed to speed the drying process in the freezing temperatures at Knole!). Using a combination of gluing, wedging, and tying all of the monitors have been successfully attached.
John Hartley preparing the sensor mount (left) and the finished sensor (right).
These monitors are designed to pick up the tiniest cracks and pops emitted by the furniture as it reacts to the environment around it. The relative humidity (RH) in the Showrooms of Knole can cause certain materials such as wood and metal to expand and contract as it fluctuates. It is impossible to tell how much the objects themselves are moving with the naked eye and so this AE method has been developed to help us better understand what seasonal variations in RH are doing to our collection. The sounds the equipment are monitoring for are so tiny they couldn’t hope to be heard without these specialist sensors.
Sensors have been attached to 4 objects in the house; the Gole table and a torchere in the Great Store and the Jensen table and a torchere in the Spangled Bedroom. Selecting these objects allows the researchers to compare the effects on similar objects in varying conditions. The Spangled Bedroom currently has no environmental control at all. This means the the temperature and relative humidity change with the weather conditions outside with no human intervention. The Gole table in the Great Store however is subject to environmental control which keeps the relative humidity below 65% at all times.
The ideal conditions for a mixed material collection in the National Trust is between 40% and 65% although this is not always possible. Part of our long term conservation project at Knole is to try and install environmental control throughout the Showrooms so that the RH can be carefully controlled.
The AE project will run for a full year from now and it will allow us to understand and better manage the change from an uncontrolled to an RH-controlled collection. The sensors and laptops will be left in their current positions permanently and will be checked remotely from Poland once a week to make sure everything continues to function properly.
It was fascinating to see researchers and conservators of different disciplines come together at Knole to put this project together. Hopefully it will yield some interesting results!
Thanks go to Nigel Blades and everyone on the AE project team for providing the information and pictures in this weeks blog.