Thursday, 10 March 2016

VIBRATIONS: NO EXCITATIONS IN CONSERVATION

CONSERVATION TIPS & TRICKS

BY: NIKITA JOHNSTON

As most who work with collections know, it is the handling and moving of collections and objects that often poses the most danger. When packed away in storage or placed in display cases, most objects fair relatively well, even with light, humidity and dust posing potential risks. However, there is another unseen danger that must be considered by those who care for collections, and that is the danger and damage that vibrational forces can pose to collections.

The vibrations most commonly encountered in museums, historic houses and historic sites are a consequence of visitor circulation. Vibrations caused by foot traffic can be particularly pronounced on poorly supported wooden floors, found in older buildings. Objects displayed in drawers can also suffer from vibrations as the drawers are opened and closed, shifting inside the drawer each time. Vibrations can also be caused by construction work on nearby buildings, heavy road traffic or roadwork, subway systems and trains, and in the case of the St. Catharines Museum and Welland Canals Centre, by ship traffic through the Welland Canals locks. Finally, in many parts of the world earthquakes and the destructive damage they can cause through vibrations is a very real threat.

Man made vibrations! Source

Vibration can cause damage through a number of mechanisms. Toppling is a serious concern during earthquakes, but less likely from flooring vibrations. The forces caused by vibration can directly damage weakened or fragile objects, particularly ones with friable pigments, unsecured components, and loose corrosion products. If objects are restrained or supported by mounts, impact with the mount through vibrational forces could damage the piece, or cause abrasion of the surface. Unrestrained objects have been known to move or ‘walk’ on shelves under the influence of vibrations, even subtle vibrations caused by foot traffic. ‘Walking’ objects can impact with other objects or fall of shelves.

While an earthquake can be disastrous, there are some relatively simple steps that can be taken to ensure that objects in storage and on display are not damaged by vibrational forces.

In storage areas, fragile materials and those prone to toppling because of their centre of gravity can be stored in boxes with dividers. The St. Catharines Museum and Welland Canals Centre uses this method for storing glass bottles.

Glass bottles are kept in plastic containers and padded with foam to mitigate damage caused by vibrations from the ships moving through the lock at the St. Catherines Museum and Welland Canals Centre. Nikita Johnston, 2016.

Objects in storage can also be supported by sand snakes.

Not those Sand Snakes! Source

No, not the Game of Thrones Sand Snakes, but weighted snakes or bags like those below. Made from simple cotton sleeves filled with either washed sand or metal weights, they can be coiled around the base of the object or place inside to lower the centre of gravity and give them additional stability and support.

Weighted bag filled with metal shot. Source

Within storage areas, bars or straps can be purchased or retrofitted to shelves to keep objects from falling off, and can be padded out with foam to avoid damage through impact. Rolling compact storage when kept closed provides additional protection as objects cannot fall out or between the closed shelving.

Fabric straps have ben installed on some of the shelves holding ceramics at St. Catherines Museum and Welland Canals Centre. Putting foam in between the ceramics would provide additional protection against impact if they 'walk' into each other. Nikita Johnston, 2016.

The Museum of Anthropology UBC has come up with a simple but successful mounting system referred to as black trays that are used for objects both on display and in storage. The mounting system was developed not only for earthquake mitigation, but is useful for objects installed in drawers as a stabilizing measure against drawer bounce and slamming. The trays support the object by utilizing a stable, non-reactive, high-density foam product (Plastizote Foam) that should maintain its shape and provide support for many years. The trays also reduce direct handling of the objects they support. Instructions and a supply list for these trays can be found here.

A simple black tray designed by the Collections and Conservation staff at the Museum of Anthropology, at UBC. © MOA UBC, Vancouver. Source

For objects on display, supports and mounts should be padded out to reduce impact damage and abrasion caused by vibrations. Non-porous objects on shelves can be fixed in place using a small amount of museum wax, or objects  can be placed on a thin sheet of Plastizote, which should keep them from ‘walking’.

This crayfish salt cellar at the Victoria and Albert Museum won't be 'walking' or 'crawling' anywhere, now that it sits on a sheet of Plastizote (V&A C.73-1938) © Victoria and Albert Museum, London. Source

Coming from a number of different sources, both man made and natural, vibrations can pose a risk to collections. But, those caring for collections simply have to...




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