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This blog is a behind the scenes look at the Roman Baths in Bath. We hope you enjoy reading our stories about life surrounding the Roman Baths.

Wednesday, 14 December 2011

How To Let Your Objects Know You Care

Museum objects need to be cared for, especially because they are extremely old, so proper handling and storage is very important. When handling objects, the first thing you really need is common sense – like knowing you shouldn’t throw objects around or make tea with one in your hand! It’s also useful to have a gently padded strong surface to place objects on, and to wear gloves.

Gloves are incredibly important when handling all objects, but particularly when working with metal. This is because your skin constantly secretes sweat, which contains all sorts of nasty chemicals that can actually etch into metal surfaces! Sweat also contains potassium lactate, which means that the fingerprints will attract moisture and cause dust to cling to the surface, risking corrosion and mould growth. Wearing gloves stops your fingerprints from attacking the object.

There are also plenty of airborne pollutants that can cause damage to artefacts without any human contact. In the air outside, chemicals such as sulphur and nitrogen dioxides cause metals to tarnish, and affect other objects too; damaging textiles, dyes, and photographic materials. Objects containing calcareous materials like limestone and bone can also be affected by chemicals in the air such as acetic acid from glues and sealants.

To prevent objects from all sorts of dangers, including physical damage, pests, dust, pollution and light, they are stored in polythene boxes. These also buffer changes in temperature and humidity. All the packaging involved, including the box, should be inert and as non-biodegradable as possible to prevent any chemicals from leaking out and causing damage.

Not your average lunch box: A storage box holding boxed objects safely cushioned in acid free tissue.
Objects are packed in nests of acid free tissue, and the climate within each box can be controlled with silica gel, which is conditioned to maintain a specific humidity level by absorbing moisture from the air. The most commonly used silica gel changes colour when it needs to be replaced, and can dried by gentle heating for reuse.

The graph below shows the different conditions preferred by various materials, for example wood is best preserved in a very humid environment, whereas metals require the air to be much drier. When an object is made of more than one material, it is much harder to protect, but it could be kept at a mid-range relative humidity to prevent any damage.

Graph showing recommended ranges for relative humidity
 If you would like to learn more about how to care for objects why not come along on a ‘Behind the Scenes Tour'? see the link below for forthcoming dates…


More about our 'Behind the Scenes' Tours in January....

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