We’ve all been there – picking up your bread in the morning ready for breakfast only to find it spotted with that horrible white and green fluffy stuff…mould. You may even been unfortunate enough to have suffered with mould outside the kitchen perhaps on the walls of your house or in particularly dark and damp areas. Mould can be an awful unsightly pain but even worse its a health hazzard and can cause long term damage to your possessions. Historic houses are by no means immune from the problem and we and many other properties face mould battles throughout the year. You can find some great blog posts all about other National trust properties for example Knole in Kent often have to deal with issues of mould and have even studied the growth of mould in their environment, check our their conservation blogs for more information.
This week we will be closing the Dining room at Polesden Lacey for three days while we deal with a mould outbreak. The house suffered with high relative humidity over the winter period and as a result we are taking action to remove the mould that has grown in order to prevent it from damaging the house and collection any further. The Dining Room will be closed for three days from the 29 June to 1 July, reopening on the 2 July. As a result one of Mrs Greville’s most expensive paintings “the Paterson Children” is going on tour to the west corridor of the house. Today we have rehung the painting ready to be seen in its new location by visitors.
What is Mould?
So what exactly is mould, why does it grow and when are historic properties most vulnerable? Mould is the name given to the visible growth of Fungi. we often see it growing on “dead material” such as textiles, wood, leather and on damp walls. Mould can appear as a white fluffy substance growing in spots, but as it develops can change colour and become more vivid in colour. The mould in the dining room is still white and fluffy – hopefully we have caught it before it develops further. You usually see darker coloured mould in damp conditions, we had some grow in the billiard room earlier this year on an exterior wall. We were able to remove the mould and treat the area to prevent regrowth.
Why does it grow?
That horrible white fluffy stuff is made up of mould spores – and spores are always in the air around us. The environmental conditions of the room can have a great impact of the growth of mould. A high relative humidity (read more about relative humidity here) means that there is a greater concentration of mould spores – usually when relative humidity is greater that 65% – and the room is particularly damp. If the room is not well ventilated the trapped air will promote the growth and settling of the mould spores. Mould spores can lie dormant for a long period of time and when conditions are right they will germinate and spread.
How do we deal with mould?
Mould can be toxic to health as well as to the objects in our collections so we deal with it in a very specific way. If the room was particularly damp we may choose to use dehumidifiers before hand to dry the mould out, however this wont be necessary as the dining room is currently within the desired humidity levels. Mould Spores are ever present in the air in small quantities but once an outbreak is disturbed more mould spores can be released into the air. We have closed the room to the public so that only staff wearing the correct Personal Protective equipment (PPE) will enter the room while cleaning is in progress. Each member of staff will wear a disposable white Tyvek suit which covers all their clothes and hair, a specially designed mask which prevents the user from breathing in mould spores, gloves and protective eye wear. The important thing about this PPE is that it is all disposable or washable. It must only be used once so we set up a clean area outside the room where each person can remove their PPE afterwards and dispose of it safely. Any non disposable items will be disinfected afterwards. Next we must make sure that the collection in the room is covered and protected. Once we disturb the mould spores there’s a possibility they could land on collection items and we may be faced with a new outbreak. The collection will be covered for the duration of the clean and the covering disposed of afterwards. Once the room is prepared we have to make sure we have the correct equipment to tackle the job. Using specialist brushes we will gently brush the mould into vacuum cleaners. These vacuum cleaners are all fitted with a HEPA (High efficient particulate arrestance) filter. The filter traps the mould spores rather than dispersing them back into the air. With some materials we can then sterilize the area using ethyl alcohol and water, however this will stain some materials so we only do this if it is necessary.
We hope that this process will take us around 3 days to complete, once the mould has been removed from the silk we will monitor the environment and the walls carefully to ensure that there is not another outbreak. In some cases repeat action is necessary a few months later, it is important to keep up regular environmental monitoring and ensure the room is well ventilated.
Why not come and see the Paterson Children in its temporary home and although for health and safety reasons we cant allow visitors to see us cleaning the mould in the dining room we will be presenting information about the clean outside the dining room for all three days.