Despite being a nice break away, from hectic city and business life. A couple of days in a beautiful historic building in the middle of a green valley with a fresh river & roaming sheep with their new baby lambs seemed to sooth the soul.
West Dean was an eye opening experience to learn Masonry Cleaning.
Starting with an evening lecture on the first day (very different)
We had a look at some of the old ways of cleaning buildings.
Before the times of heat, pressure or abrasive methods, people used to literally scrub buildings, statues and monuments by hand.
With very little safety to add, with men literally hanging off statues tens of metres into the sky.
Another popular method used back then was continually soaking buildings with copious amounts of water to loosen what was mainly heavy deposits of soot back in that time. Then scrubbing with bristled brushes to remove some of the heavy surface staining. A painful, time consuming job to say the least.
Even the fire Brigade back then would regularly get involved in ‘cleaning’ or soaking public buildings with copious amounts of water to rinse them down.
The second day, we started in the classroom and got an overall understanding of what causes buildings to get ‘dirty’.
The use of inverted commas to highlight the fact that this is often completely natural and organic.
The main take away from the morning was the how buildings in urban areas can often be dissected into three types of areas when you look at them.
The areas most exposed to the weather, the areas most sheltered by the weather and the areas in between.
What’s interesting here is the difference in soiling between the three areas. The areas most exposed, have the most organic growth and the least carbon staining.
Whereas the more sheltered areas suffer from the highest carbon staining and little organic growth. The areas in between are often the cleanest in appearance, as they almost receive a natural wash from the rain water without allowing water to build up for a long time.
Building design can play a huge part in how a building looks into the future and how it reacts to the elements.
Square and flat surfaces were very popular with architects but often little though has gone into how water will behave when it hits the surface
Anywhere where the patina can remain damp for long periods is going to lead to organic growth in these areas such as alga, lichen and moss growth.
Drip detailing is a way of channelling water away from the substrate to prevent build up.
Architects and developers also need to be careful with the materials selected as metals such as bronze., lead and copper can all cause salt deposits in stone or brickwork which appear to produce staining.
This can be on the surface or even beneath the surface in more porous materials making it harder to remove.
Surface and sub surface Staining
The main types of surface stains include carbon, organic and other man made products like paints.
All of these can also migrate beneath the surface in porous materials.
That’s why you need to be super careful when trying to remove the stain to ensure you are not removing the substrate at the same time to try and get down to the stain if it has gone sub surface.
Possibly the most effective way of removing sub surface staining therefore is by using poultices or gels which draw the sub surface stain out to the surface so it can be removed.
The practical part of day two involved us using some of these poultices on some sample sandstone slabs.
With a mixture of graffiti, cement based paint, acrylic paint and even linseed oil and permanent marker pen being our sample contaminants to try and remove.
With a range of methods at our disposal to use including
The Thermotech machine
The wet abrasive machine
Small dry abrasive machine
Poultices , gels, paint softeners and dry steam machine
It’s here where we really learnt the importance of trying to establish exactly what it is you are trying to remove.
For example the paint type. As different types of paint would have completely different removal methods, with some methods being completely useless against some types of paints
It’s here we were also introduced to the Mors
Hardness testing kit
Where you can test the hardness of the ‘stain’ you are trying to remove as well as the substrate.
In an ideal world the item trying to be removed is a lot softer than the material you are trying to remove it from.
Especially with any wet or dry abrasive methods. This would mean selecting an aggregate which is harder than the hardness of the stain, but less hard than the hardness of the material the stain is on.
This would give the best chance for a successful removal with the least risk of damaging the substrate.
To end the evening we had a lecture on war monument cleaning/ restoration David was the director of Nebulous.
From a conservation background before the time of the internet, his knowledge and expertise made him a man high in demand all over the world for cleaning old buildings and monuments.
His latest project being a four year internal clean of St Paul’s cathedral
He spoke about how soo much damage has been done to these monuments over the years by wrong cleaning methods , too much cleaning and sometimes Poor initial design.
An interesting belief , which he disagreed with, but believed the large majority of the public supported, was that to show respect for the people these monuments represent they must remain regularly maintained and ‘clean’ in appearance.
His view which was slightly controversial to hear on a cleaning course, that often the correct course of action is not to clean them at all
That most methods of cleaning will actually open the pores of the stone and make the stone more susceptible to growing algae’s and getting dirtier more quickly, therefore requiring more and more frequent cleaning.
He spoke about trying different stone sealers on these monuments and how sealers are not in his opinion the correct solution, as just like anything they break down over time and can lead to trapped moisture.
He spoke about how biocides are not the answer as they can pollute local waterways for one, but also are becoming less and less effective.
What was really interesting is that essential oils for monument cleaning has proved highly effective in Sone areas of the world with more test and development being done on low concentrations of essential oils for the removal and prevention of organic growth (watch this space!)
The other thing covered was; Covering in
This is where stone masons close in the pores of stonework where it has opened.
This changes the surface of the stone to make it less porous and reduces the amount of space where organic growth can grow.
On the final day we had a closer look at the different types of stone used in building materials.
Certain areas and cities have a particular stone that is most common in building use, this is often due to the location of nearby quarries and the stone available at the time of building.
We looked closer at the porousity of stones and how to test how porous and permeable a stone type is with two main tests
The very simple water drop test and also the ( insert name test)
Where you use a plastic device and some putty to seal the device to a stones surface , fill the tube with water and then record the time it takes the water to penetrate into the stone.
This information is useful in distinguishing whether certain stones or areas of stonework on a building are allowing water through and even if any sealers have been used to prevent water penetration. This type of test could help to verify the cause of damp issues and help people understand why covering natural stones with man made paints or cements often results in damp issues.
Laser for cleaning
I wasn’t expecting to get the opportunity to try out a £30,000 laser for cleaning on this course. I had watched videos on line of these tools stripping carbon effortlessly from brickwork and thought could this be the next big thing?
However like all cleaning methods it has its strengths and limitations.
The laser was good for removing dark staining such as sulphation or dark paints while causing minimal effect to the substrate. It was very useful for removing staining from
Biological Growths
Bacteria, Algae and Cyanobacteria ( slimy white) , Fungi, Lichen and Moss all grow naturally especially in damp conditions. These growths like porous materials .
Lichens are a combination of algae and fungi living in symbiosis.
For these organisms a regular light clean can be the most suitable. When trying to kill these growths the local surface temperature needs to reach at least 60 degrees, for this reason super heated systems like the DOFF or Thermotech Systems are the most suitable.
To summarise there are many different methods for masonry cleaning. and restoring buildings, each method has suitable applications depending on what is trying to be removed.
Depending on whether the surface staining is flexible or brittle will determine whether a wet steam cleaning is more suitable ( organic flexible staining) or an abrasive method is more suitable ( brittle staining eg carbon)
Even when the most suitable method of masonry cleaning. is selected the task of cleaning without causing damage or causing minimal disruption to the surface as is more likely comes down to the operator. A highly skilled & experienced operator who cares about the petina of the building will perform a much better cleaning task that an inexperienced operator who just wants to get the job done quickly.
The best practice for ensuring buildings can remain clean looking without leading to increased deterioration is by cleaning earlier on before any staining reaches a level that requires stronger methods for removing the staining. As these understandable risk causing more damage to the material being cleaned . To sum up clean early, clean often and clean carefully.
