Church Monuments Society


How Not to Clean a Monument

By CMS in CMS news, Heritage

A lot of us were worried by this article in last week’s Observer

The article was describing with what seemed like approval attempts to clean gravestones with acid and steel scrubbing brushes. Several of us took to social media to explain, with as much detail as you can get into a tweet, why this was Not A Good Idea. At the AGM last Saturday I was able to discuss it with our Conservation Officer, David Carrington – here is his response.

‘This is truly appalling! If the article is to be taken at face value the grave markers are white marble. The sizzling of the stone is the marble literally being dissolved – no wonder it’s clean. But the stone is gradually getting eaten away, and the surface is left more open so that organic matter will recolonise more quickly, so it’s a short-term and unsustainable solution.

‘Steel brushes are a bad idea as (a) the steel is harder than the marble so will physically abrade it and (b) tiny little flecks of iron can sometimes be left on the stone leading to disfiguring rust spots.

‘Using hydrochloric acid is a serious health risk (erm, ‘coughing as acid vapours blew in his face’ – lucky it didn’t splash in his eye) as well as bad for the environment.

‘If headstones are to be cleaned I advise carefully removing moss by hand followed by scrubbing using bristle brushes (such as a tooth brush or nail brush depending on context) and accepting a certain level of retained patina. One needs to know when any cleaning might be causing damage, and there is a danger that less durable stones could be damaged. For example, a fissile sandstone slab might be best just left alone.

‘Even without acid cleaning one has to accept that carved stone outside, especially in a hostile environment, does not last forever and recording inscriptions and keeping those records in an accessible place is an important facet of conservation.

‘But under no circumstances should cleaning any sort of grave marker with hydrocholric acid and steel brushes be encouraged.’

It’s understandable that people want to keep gravestones clean, tidy and legible – but the message is, do as little as possible, as gently as possible and as carefully as possible. Ultimately, you have to remember that good conservation practice never does anything irreversible, and that it is often better to do nothing at all.

The Church Monuments Society is always happy to advise on conservation, or anything to do with monuments. You can contact us using the contact form on this web site.

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