Hello all, I promised a while ago to give you some more details about materials that can be used to protect silver.
There are many products on the market, however not all are suitable for protecting our silver in the store, as we need a long-term solution and therefore a material that will last. One obvious option is to cover each individual object with a tarnish protection layer, such as a surface lacquer; however this is very time consuming and may not be suitable for contemporary pieces, as some have clear instruction by the artist and maker of how they should be kept and cleaned.
There are also M3 anti tarnish strips, they are special absorbent paper strips that absorbs sulphides and other pollutants that cause silver to tarnish. They are placed in a sealed container with an object and last for about six months, so again not really a suitable long term option. So at the moment the following three materials seem to be the most suitable for this project: Tranprufe, Charcoal Cloth and Intercept.
Tarnprufe (fig 1) is a textile that has been impregnated with a zinc salt and sodium carbonate that reacts with the hydrogen sulphide (the gas that affects silver, leading to a tarnished surface) in the air and neutralises it. Once all of the reacting molecules have been exhausted, the bag looses its protective purpose. The objects need to be fully covered by the material and some conservators have experienced a 13 year life expectancy. The only down side being there is no obvious indicator as to when the fabric is exhausted, so there is no way of telling if the bag still protects the silver, unless you sent the bags off to be tested in a laboratory but that can be quite expensive.
Charcoal cloth (fig 2) works on a similar basis as the Tranpruf bags, but it uses activated charcoal as a mechanism, as it has a large surface area to absorb pollutants. It can be ordered in large sheets with various thicknesses and then cut into the shape that is needed.
It is not recommended to use this material in direct contact with the silver objects, so it is advisable to use a barrier layer such as acid free tissue or melinex.
This has highly reactive copper particles, bound into a polymer matrix (fig 2). When the copper turns black all the reactive molecules have been exhausted and it needs to be replaced. This is very useful as it enables us to see if the bag needs changing. The manufacture suggests that 1mm thickness will give about 10 years protection.
So far we have put some of the objects into already existing Tarnprufe bags and we are still in the process of deciding how to protect the remaining objects in the store, it probably will be a combination of materials stated above.
I am afraid this will be my last blog as my time at Birmingham Museums Trust has come to an end. I hope you found this blog useful and interesting.
ICON HLF Intern in Preventative Conservation
Hi my name is Rose I am the new, ICON intern in preventive conservation at Birmingham Museum and Art Gallery and I will be here for 12 months. ICON (Institute of Conservation) gives people the great opportunity to gain valuable work experience through their internship scheme by closely working together with institutions such as Birmingham Museums Trust. These internships are funded by the National Lottery Fund.
My background, I have recently been awarded with the Masters in Conservation of Historical Objects from Lincoln University and with a degree in History of Art with Museum Studies. My practical work experience within conservation and the heritage sector is as a volunteer. I feel very lucky to have been given the opportunity by ICON and Birmingham Museums Trust to work as part of a professional team to gain some much needed work experience in the field of conservation. I am particularly interested in preventive conservation and collections care, because I believe preventing objects from damage should always be the first approach when dealing with heritage objects.
Being a preventive conservation intern I am involved in a large number of projects related to collections care. This means I am dealing with objects that are on display in the galleries but also objects that are in storage. For example one of my key roles is looking after the Hanwell environmental monitoring system that records relative humidity (amount of moisture held in the air) temperature and light, as any of these factors can have long term damaging affects if not controlled. My role in relation to this is to check the incoming environmental data for any abnormalities.
Rose checking the Hanwell environmental monitoring system at BMAG.
When objects are not on display in the gallery they need to be stored in a stable environment for their long term preservation, so a big chuck of preventive conservation deals with creating suitable storage solutions. As an intern I have been given a project to assess the silver collections storage environment. Silver is quite vulnerable to gaseous pollution as it easily tarnishes, which can be quite disfiguring. Unsuitable gaseous pollution can be given off by various things such as other objects, made of other kinds of materials, in close proximity.
To see if there are any particular areas of concern in the silver store I have started to set up an environmental monitoring system that records relative humidity and temperature, as high relative humidity in collaboration with gaseous pollution can support tarnishing.
The button loggers that record the temperature and relative humidity in the silver stores.
In January I will also place little samples of silver, copper and lead throughout the store to see if they react to the surrounding environment, which could indicate if there is a problem of gaseous pollution.
Video of Rose explaining the environmental monitoring of the silver collection stores:
This kind of assessment can take up to a year and will be my main, ongoing project. Please check my blogs for updates on my progress.
ICON HLF Intern in Preventative Conservation