What lurks under the microscope? Dust detective work

On the surface of it, dust can seem like a mundane nuisance, but it's of great interest to Scientists and Conservators who can zoom into this hidden microscopic world. Staff across the Museum work together to rid the galleries and stores of this dusty danger, helping to preserve and protect the collection.

Layers of dust can obviously affect an object's appearance, but dust can do more than just impact on the looks of an object. Dust poses a health threat to humans, and can also be a risk to museum collections.

Dust has been identified as one of the 'ten agents of deterioration' that can cause damage to museum collections. It doesn't just affect the aesthetics of the collections, but in combination with other environmental factors (temperature and relative humidity) it has the potential to cause serious damage to objects. This is especially true for objects outside display cases like the totem poles in the Great Court. But first, let's take a look at what dust actually is.

What is dust?

We can define dust as particulate matter that can be suspended in the air. The sizes of these particles vary from really small with a diameter of less than one micrometre (μm, which is one thousandth of a millimetre), to larger particles with a diameter of 20 μm or more. The components of this particulate matter vary greatly and can have organic sources (originating from people, animals, plants and insects etc.) or inorganic sources (for example plastics, silt or metal particles). Dust can be composed of many different things – keep reading to find out what we've found lurking in the microscopic world of dust at the Museum.

How can dust damage collections?

Damage to objects can happen in a variety of different ways. Dust particles can get ingrained in objects over time, making it extremely time consuming to remove without damaging the surface material. Organic and particularly inorganic dust particles can also be abrasive to the object's surface, meaning that they slowly wear away the material underneath. Dust particles are hygroscopic (i.e. they absorb water from the air), which can corrode metallic objects. It can also contain mould spores which can thrive in certain temperature and humidity conditions. Mould can stain material surfaces as well as affect their structural stability, and mould spores are also a health and safety concern for people accessing the collections.

Lastly, dust and debris with organic particles in can be a source of food for insect pests that could cause damage with their activity. Common insect pests in a museum setting might be the webbing clothes moth Tineola bisselliella and carpet beetles Anthrenus and Anthrenocerus.

Knowing what type of dust is present, as well as its source, is useful so we can prevent or mitigate its potential damage as much as possible. Using different scientific tools we are able to be transported into a fascinating microscopic world and see what hides behind that familiar layer of dust.

How do we analyse dust at the Museum?

First we need to sample the dust. We do this by using carbon-based, electrically conductive, double-sided adhesive discs on microscope slides to collect the dust that will then be analysed under a scanning electron microscope (SEM). We then place the glass slides either on the object or on the plinths surrounding the object – eagle-eyed visitors may have seen some of these around the Museum. After four weeks, we collect them and take them to be analysed in the lab.

Behind the scenes in one of the Scientific Research laboratories, we analyse the dust samples using the SEM. The SEM can produce high-resolution images by scanning the surface of the sample with a focused beam of electrons. This gives us a lot of information about the topography (features on the surface) of the samples and can see details down to about 5 nanometres (nm). This means that we can see very small insects or grains of pollen in a lot of detail. The SEM can also be paired with an energy dispersive X-ray spectrometer (EDX), which allows us to identify the chemical elements present in the samples so we can tell if a small piece of something that looks like a seed might actually be a piece of metal.

What does dust look like under the microscope?

Looking at the samples under the SEM allows us to see dust in a new light, and reveals so much more than we can see with the naked eye. Some images can be easy to recognise – like insects or fibres – but others were surprising. Small things can look very different up close! Have a look and see if you would recognise our findings.

The work we do at the Museum to protect the collection from dust is a good example of collaborative work across the institution. It requires several departments and colleagues to work together to identify its constituents, understand the risks associated with the particulates present, and work on different strategies to mitigate against them.

Top ten tips for keeping your home dust-free

If all this talk of dust has got you preparing for a spring clean, we've compiled our best advice to keep your home and any artworks free from dust!

• Frame your work
• Display art in a closed cabinet or sealed case
• Move it away from an open window
• Have an entrance mat to remove dirt from your shoes
• Clean and vacuum the nearby area regularly
• Use a dry, soft brush to carefully dust off a sculpture or painting
• Use a damp microfibre cloth to gently wipe off dirt or stains and then a dry cloth to remove moisture from a ceramic surface
• Use a dry, soft brush to remove dust or a small air brush to blow away any dirt from a photograph or print
• Use a vacuum with adjustable suction and small nozzle on your tapestry or textile through a mesh screen
• Read The National Trust Manual of Housekeeping for more comprehensive information!

Read our colleagues' blog post to find out how we went about removing dust from an 18th-century suit of samurai armour.