Hello everyone! As this week is all about the objects and artefacts we have here at the museum service we thought a blog about conservation and the threats to the objects in our collection might be an interesting topic for you to read about. So without further ado, here are the threats we face, and how we tackle them:
(measured in ‘Lux’ -used to measure the intensity of light hitting a surface)
I’m sure we have all seen something in our lives that has been bleached by the sun, whether that’s garden furniture or curtains near a window or a wall where a picture has been. This phenomenon, unsurprisingly, can do a tremendous amount of damage to museum artefacts. The best way to combat the effects of light on museum objects is to reduce the amount of natural light directed onto them. At Sandwell Museums we use blinds to block out the sun, use solar control film, which has a tinting effect which filters out the harmful amount of light but leaves enough for people to see. Plus of course, keeping the most light-sensitive objects away from windows. These are some examples of materials most affected by light:
– Costumes and other textiles (which is why we keep the blinds down in the bedrooms at Oak House and Haden Hill House.
– Fur and feathers
– Dyed leather
Here we see how light has bleached a tapestry, reducing how vivid the colours should be. (blog.hrp.org.uk)
(measured in degrees Celsius)
Temperatures between 10 and 20 degrees Celsius are what we aim for, as anything less is too cold for visitors, and anything higher is both a bit too warm for staff and visitors and can also speed up the deterioration of some museum objects. Museum stores can be colder than ten degrees as they don’t tend to see many visitors aside from staff. It’s also very important to ensure that temperatures don’t change from hot to cold and back again too quickly. As this can have a freeze-thaw effect on artefacts, whereby the heat makes the material expand, and the cold makes it contract, leading to cracking and shattering. Thermometers are the tried and tested method of measuring temperatures, if an area is discovered to be too cold, heaters (or central heating if applicable) can be used as long as they are set to a low temperature. Fortunately, being in the UK, rooms being too hot are a fairly rare occurrence, however, when this happens ventilation, if possible, is the preferred option though in some cases artificial fans and air coolers can be used.
Here we see the freeze thaw effect on rock, whilst the interior of museums never get cold enough for ice to form, heat and cold causes similar damage. Objects expand in heat and contract in cold. (twinkl.co.uk)
(measured in ‘RH’ – ‘relative humidity’)
Humidity (the amount of moisture in the air) can have a very serious impact on museum artefacts, if there is too little in the air, artefacts can become dry and brittle, which can do permanent damage, even if humidity is returned to acceptable levels within a short time frame. Relative humidity should not drop below 40% or rise above roughly 70%, as too much moisture in the air encourages fungal growth. When that happens, even if the fungus is removed the stains left can be permanent. To measure relative humidity we use devices called hygrometers, which act in a similar way to thermometers. To combat the effects of too much humidity we have a number of dehumidifiers, and in areas with too little humidity we have humidifiers. (Visitors to Wednesbury Museum and Art Gallery may have seen a pair in the Richards gallery).
Here we can see evidence of mould staining some wooden furniture. (environix.com)
Pests probably constitute the biggest threat to our collections as they’re rather good at sneaking in and setting up shop without anyone realising. I have included some pictures of the main culprits, which are carpet beetles, clothes moths and woodworm.
Carpet beetles, as their name implies, tend to infest carpets. However, they will also eat any other items composed of wool, fur, felt, silk, feathers, skins, and leather. Such materials contain keratin, a fibrous animal protein which their larvae are able to digest. Cotton and synthetic material like polyester and rayon are rarely attacked unless blended with wool, or contain food stains or other natural materials.
A Varied Carpet Beetle. (inoculandpestcontrol.co.uk)
This is an example of the type of damage they do to carpets. (thesuffolkpestcontrolcompany.co.uk)
Clothes moths, behave in a very similar way to carpet beetles, they destroy fabric and other materials. They feed exclusively on animal fibre, especially wool, fur, silk, feathers, felt, and leather, as these materials contain keratin, a fibrous protein that the worm-like larvae of the clothes moth can digest. In nature, the larvae feed on the nesting materials or carcasses of birds and mammals. Which means that when museums have birds nesting in the roof, or any rodents on site, it is actually a very serious problem! Serious infestations of clothes moths can develop completely undetected until it’s too late, causing permanent damage to vulnerable artefacts.
This picture shows a clothes moth and the damage they can do to textiles. (countryliving.com)
The common furniture beetle or woodworm, is believed to be the main cause of damage to timber in the UK over the last 100 years! During the last 50 years, insecticidal treatments have been widely used to treat timbers in buildings thought to be at risk. The worry of woodworm infestation has become so integral to the culture of property management and building repair in the UK that most buildings which are more than 50 years old have been treated at least once, and many have been treated repeatedly on each change of ownership!
This floorboard showed absolutely no evidence of infestation by woodworm until sanding and polishing revealed tunnelling beneath the surface. (buildingconservation.com)
This is what woodworm actually looks like when munching through wood. (rentokil.co.uk)
To tackle the issue of insect pests all museums will use pest traps to monitor what creepy crawlies are visiting the site, with having 6 of the same type of pest warranting an infestation. Of course not all insects and spiders are a problem, we have to look carefully for the critters we’re concerned about. It is the job of staff on site to periodically check the pest traps and report their findings – this isn’t their favourite task! If an infestation is detected measures must be taken to isolate and remove the infestation. This will sometimes involve literally removing an object from the collection and putting it in isolation, to prevent the infestation spreading. To actually kill the insects, depends on what material is currently suffering from infestation. Some examples of treatments are:
Low temperature treatment, whereby an object is placed inside a specially designed freezer which kills the insects without damaging the object.
High temperature treatment, similar to the above method, however this time the temperature is raised. A short exposure of no more than 55 degrees Celsius.
Controlled Atmosphere Treatment, in this example, an object is placed inside an air-tight container and carbon dioxide is slowly pumped inside. The lack of oxygen leads to increased respiration, which eventually leads to dehydration of pests.
We hope you enjoyed this small glimpse of the monitoring work that goes into ensuring historic artefacts remain in as pristine condition as possible here at Sandwell Museums Service.
Jack – Collections Officer