Author: Ellen Moody

In this presentation Anna Serotta and Andrew Smyth presented their efforts to assess and mitigate vibrations in the Metropolitan Museum’s Egyptian galleries during a large-scale renovation of the spaces directly below. Having worked in museums that remained open during renovations, and now at one that is about to expand, I was particularly interested in the subject of construction-induced vibration, and appreciated the experiences and tips shared in this case study.
At the end of the summer of 2011, staff at the Met began preparing for the renovation of their Costume Institute to commence in April 2012. Forming a project team of curators, conservators and collection managers, and partnering with a group from the Department of Civil Engineering and Engineering Mechanics at Columbia University, the museum aimed to safeguard 20,000 objects spread over 27 galleries. The project team would first assess risk posed by the construction and then implement preventive conservation to protect objects in adjacent galleries—while allowing as many objects as possible to remain on view. It didn’t help that many of these works were fragile, consisting of friable wood, brittle basketry, ancient restoration materials, etc.  Many had not been moved for 40 years.
As the title of the presentation makes clear, the main risk of construction in a museum is posed by its vibrations. A concise review in slides titled “Vibrations 101” explained that vibrations may cause stresses, fatigue and extant crack-growth in objects. Vibration affects any object with mass and flexibility—pretty much anything. Published vibration threshold standards were designed to assess risk to buildings and therefore could not be applied to fragile museum objects.  The Met decided to take an empirical approach: piggybacking on the tests performed by the construction contractors, the project team placed accelerometers on pedestals and shelves while various demolition tools were tested below. The tests showed that machinery that was less user-dependent caused less vibration, i.e. high speed coring drill was preferred over sledgehammers. Testing also confirmed that certain mounting systems, such as cantilevered shelves, magnified vibration.
Several preventive conservation approaches to mitigate the vibrations – within the extant display strategies – were shared. Sorbethane – “a highly damped, visco-elastic polymeric solid that flows like a liquid under load” – was placed under pedestals and other mounting systems to absorb vibrations. Cantilevered shelves were stiffened by putting Sorbethane-capped posts below the shelves. Large masses placed on isolation springs were added (discreetly under benches) to the floor so that they would both absorb and dampen the floor’s vibration. Lighter objects were placed on trays with ethafoam tri-rod to keep them from shifting off the shelves.  To keep track of changes in condition, fragile objects were photodocumented in raking light, and white paper was placed under objects to make any flakes or particles that detached more visible. Lastly, some objects that could not be adequately protected under these circumstances were deinstalled and placed in closed galleries that were not affected by the construction. All in all, some 14,000 objects were isolated, padded or relocated.
Sensors were placed on pedestals and shelves and connected to a wireless network on a central server. Emails and texts would be sent to involved parties when vibrations exceeded established thresholds. Hands-on monitoring by conservators was necessary to monitor objects beyond the sensors’ range.
I was grateful to learn of the unforeseen challenges and minor damages that occurred during construction. When it came to museum objects, some friable wood and gesso powdered; an old join in a wooden figure failed, causing a piece to detach; and small objects migrated on their trays (but didn’t fall off due to preventive foam linings). Sorbethane also posed challenges: it would shift out of place if there wasn’t sufficient pressure holding it in place. Likewise, it could be crushed and lose its absorbent properties if the pressure was too great. In one alarming case, a liquid – likely plasticizer – oozed out of a piece of Sorbethane. All in all, vibrations were greater than expected and hard to predict. Sometimes they were localized and evaded the sensors, which made the additional hands-on monitoring so crucial.
At the conclusion of the talk, the presenters stressed the value of communication and ingratiation with contractors and project team members. Collection tours were arranged and chocolate chip cookies were baked for the contractors. When the vulnerability of the collections was made clear, they agreed to work in one place at a time and only during working museum hours, which in turn facilitated monitoring and shortened response time. Getting involved early (a recurring theme at this year’s meeting!) and playing nice will get you a long way in safeguarding objects as walls crumble around – or below – them.