Light

Over the centuries, many visitors have found Knole to be a dark house. Back in the 1600s, the diarist John Evelyn was apparently so depressed by greyness of ‘this great old fashioned house’ that he had to hurry out into the sunlight. Today, some of our visitors still comment on the Knole’s often shadowy interior.

 

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A house that ‘smoulders rather than sparkles’.

 

Many find this atmospheric lighting an integral part of Knole’s unique charm. But for the Conservation team, monitoring and controlling the light levels in the house is a key part of how we look after our fantastic collection. Obviously, we want our visitors to be able to see the beautiful objects. However, displaying our collection while minimising the damaging effects of light, is a constant challenge.

 

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This suite in the Brown Gallery was once a vibrant purple colour but has heavily faded in the light. 

 

When light falls on the surface of an object it provides energy. This induces a chemical reaction in the molecules of the material, which causes physical changes including the structural weakening of the fibres and a change in colour. The damage caused by this reaction is cumulative and irreversible. How vulnerable different materials are to light varies, but textiles particularly are highly light sensitive. We have the largest collection of English Stuart furniture in the world to have survived. It is internationally significant and we want to ensure that these magnificent pieces can be enjoyed for generations to come.

A key part of our work involves monitoring the light levels in the show rooms. If you look carefully at some of our furniture, you may notice small rectangular cards with a square of blue wool in the centre. These are called dosimeters and we use them to monitor the effects of light. They are placed on or near light sensitive objects and left in position for a year. Part of the blue wool is exposed while the other part is protected. When the dosimeter is removed and sent off for analysis, a measurement is made of the degree of fading. How much the blue wool has faded depends on the amount of light it has been exposed to. The conservation team also conduct regular checks to measures both the UV and the intensity of the light (lux) and we have two Hanwell LUX/UV monitors on the east and south sides of the building, which send back information to a computer in the office.

 

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Knowing the fade rate of the blue wool allows us to accurately measure how much light objects and rooms are exposed to.

 

 

The most effective way to protect our collection is by preventing it from being exposed to too much natural light. We now have case covers on the furniture in the Spangled Dressing Room, to protect the incredibly fragile and deteriorating fabric. Historically, case covers have been used to protect special pieces of furniture in grand houses from the ill effects of light and dust. Should an important person come to visit the covers could be removed to reveal the textile underneath. Our red custom cotton case covers have been carefully made by upholstery conservator Heather Porter to ensure that each piece of furniture gets the individual protection that it requires.

 

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One of our brand new case covers in the Spangled Dressing Room

 

The most damaging part of the light spectrum is ultraviolet (UV) and sunlight contains a high proportion of UV. Where possible we try to filter UV out by using a film on the windows of the show rooms. The light levels in the rooms are kept low and we only expose the rooms to light when it is necessary. However, the current electric lighting in the show rooms is inefficient and ineffective, meaning our collection is often poorly lit. This is something being addressed by the project. A scheme for new lighting has been designed by Sutton Vane Associates. Historic light fittings will be fitted with LED bulbs, which will not only significantly improve the presentation of the show rooms but will also help protect our collection.

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This is from a trial conducted at Knole in the Brown Gallery. You can see how the proposed LED lighting will not only protect the vulnerable materials but really highlight our fabulous collection.

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Volunteer Experiences

We’ve been very lucky recently to have been joined by a new conservation volunteer at Knole who’s spent a few months with us to lend a helping hand. He has very kindly written a little about his experiences with the team!

Volunteering at Knole

The single greatest and most interesting part of being a Conservation volunteer at Knole has been the immense variety of tasks and small projects that are undertaken by the conservation team.

Involving everything from cleaning 18th century caffoy fabric to waxing the lead fish tank in stone court, it is hard to say that being a Conservation volunteer at Knole entails two even similar days. With the nature of the larger restoration project at Knole, as well as the day to day running of any property of Knole’s size the outlets for conservative work is seemingly endless.

The Monday deep cleans are the best chance to work on the items which are either vast or extremely precious, requiring more time and specialist equipment than many other of the usual but by no means insignificant objects. Utilising specialist material brushes as well as museum vacuums in my opinion the most fascinating part of the deep clean has been the work on the Orangery statues as well as the Roman busts of stone court. Whilst the cleaning of the Great Screen using cloth and ladders is also spectacular, if you think the screen is not amazing enough.

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The Great Screen was built c.1605-08 when Thomas Sackville did much to create the Knole you see today. The impressive edifice is bristling with heraldic symbols.

Being involved in the caffoy cleaning project was also highly rewarding. Once again the opportunity to use specialist conservation equipment and follow the stringent methods used to transform the fabric highlighted how precious Knole’s textiles really are. This time it was novel to use smoke sponges and once again low power vacuums to restore the caffoy. I can say that the process of removing a few hundred years’ worth of grime from the fabric was the most rewarding part of all of the mini projects which I have helped with over the last two months.

The caffoy material normally lines the Cartoon Gallery. During July 2016 we gave this piece a thorough clean!

The caffoy material normally lines the Cartoon Gallery. During July 2016 we gave this piece a thorough clean!

Another untold perk of being a volunteer in the conservation team here at Knole is that you truly get to experience the full character of the property, through objects, the different conditions and periods of each parts of the house, some of which is publicly accessible. Being able to see items which the team have restored or conserved is also fulfilling and history creating in itself.

All in all I have thoroughly enjoyed what seems like a very short couple of months at Knole with the conservation team and cannot overstate how fundamental they are to the condition and running of Knole as one of the country’s greatest properties. I would recommend to anyone who has even a slight interest in conservation or history in general to give conservation volunteering at Knole a go.

-Matthew

 

Spot checks!

One of the most important things we do at Knole is keeping an eye on the environmental conditions in the Showrooms. We do this through a combination of ways. Our primary method is using individual monitoring sensors in each room that send a regular signal back to the office detailing the Relative Humidity (RH) and temperature in each space. By this method we can keep an up to the minute record of what’s going on.

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Our regular ‘Hanwell’ environmental monitors. This one is in a storage space and is showing an RH reading of 58%, right where we want it.

However, because of our current project and the work going on to improve the lighting, conservation heating and all sorts of other things it means that we don’t have proper radio monitors in some rooms right now.

 

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RH in some rooms sometimes reaches worryingly high levels. It’s essential to keep a good watch on what’s happening.

 

This means that our secondary method become more important and we have to do it more regularly. This method is using spot checks. Usually we go into each space in the showrooms and store rooms every two weeks to take temp, RH, lux and UV readings to make sure that our automatic monitoring is consistent with our handheld sensor.

While the sensors are gone in the second half of the house we send the intrepid Zena in with a hard hat and a monitor to take readings every week. This way we know what kind of conditions the historic showrooms are facing on a day to day basis in all weathers.

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Zena taking readings in the Ballroom

Oh the humidity!

One of the most important elements of conservation is making sure that our collection has the best possible environment to live in. In a house like Knole this is very difficult. It’s a large building with no heating or other environmental control. This means that the house can be at the mercy of the elements. Humidity and temperature rise and fall with the weather with no way for us to control it.

photoCondensation in the Second Painted Stair caused by high humidity (RH)

As part of the conservation project at Knole we will be having special conservation heating installed in the showrooms here. Sadly for our visitors and volunteers this does not necessarily mean that the house will be toasty and warm in winter! The heating will purely be there to control the RH (Relative Humidity) of the rooms. Relative humidity is one of the biggest problems we face here at Knole. When it is too high it causes condensation to build up on vulnerable surfaces, attracts dust and makes a perfect home for mould. It can also create perfect conditions for all sorts of pests such as woodworm and deathwatch beetle. When it is too low it can cause some materials to contract and crack, veneers to lift and glues to fail.

Because of the importance of RH and temperature we have to keep a very careful eye on conditions in the showrooms. If there are particular anomalies such as high RH where it is usually lower we can investigate what has happened. Perhaps there is a leak or a heater has failed. Although we don’t yet have control over the showroom temp/RH we have been able to have some control in some behind the scenes areas at Knole. We have special humidistats in special stores that will react to the Rh in a room and turn on heaters when necessary.

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 Humidistat in the storerooms.

The primary method we use to monitor RH is our Hanwell environmental monitoring system. If you visit Knole you may see the sensors dotted around the galleries.

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Here you can see the Painting Store monitor. It has an LCD display showing you the RH and temperature at the time.

 

Each room has a box and each box is equipped with a transmitter that relays the information it’s gathering to a computer in the office. This then plots a graph that allows us to see trends and patterns in individual spaces.

Within the National Trust we try to aim for an RH level of 40-60%. This represents the amount of water vapour present in air as a percentage of the amount needed for saturation at the same temperature. Because National Trust collections are often so varied and in historic settings there is no perfect RH that is ideal for all materials but this range gives us the best chance.

To make sure we have the most accurate readings possible we also take spot readings on a regular basis. This involves taking a handheld RH/temp monitor into each space and taking an extra reading. This is a good way to make sure we are obtaining accurate information. This is also our primary method of keeping an eye on RH/temp in the part of the house currently undergoing conservation work ready to be opened again next year.

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Here is Zena taking environmental readings in the Ballroom during the conservation work.

Knole suffers with frequent high RH which will be addressed when we have our new conservation heating. Until then we do what we can!

 

A Day in the Life of the Conservation Team

 

In a sense the title of this blog is a bit of a misnomer, because no two days at Knole are ever the same. Every day is different and it’s partly the variety that makes Knole such an exciting place to work. However, it’ll hopefully give you a flavour of what we get up to, day to day, in order to look after this magnificent house and its collection.

The work of the conservation team changes with the seasons. Over winter, when the house is closed, we are busy working in the show rooms, condition checking and deep cleaning the rooms and the all the objects in readiness for re-opening.

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Zena cleaning the textile of a chair during winter before carefully condition.

 

This winter has been a bit different because of the project. Although the first half of the house (from the Brown Gallery to the Leicester Gallery) had its normal winter clean, the second half of the house (from the Ballroom to the Cartoon Gallery) was emptied in preparation for the project work that will be going on in there this year. You can see some of the collection from the second half on display in our Great Store.

Now the house is open, our routine changes. In the morning, we spend the first few hours when the house is closed getting the show rooms ready to open. Every room is vacuumed to pick up anything left behind by our visitor’s footwear the day before. We also dust any flat surfaces in front of the rope barriers and check to make sure that no cobwebs have appeared overnight. Any glass is cleaned to get rid of dust or finger prints. The blinds are set, the curtains are opened and then we’re ready to welcome our visitors for the day.

 

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One of several long galleries at Knole that need careful attention every single day.

 

There are several reasons why we do this daily clean in the showrooms. Obviously we want the house looking its best, so people can fully appreciate the incredible collection that we have here. But it’s also a vital part of the preventative conservation work carried out by the conservation team. Monitoring the environment and general good housekeeping is the first step in combating the deterioration of our unique historic collection.

The afternoons at Knole vary hugely. Some days we are in the house working on various objects in front of our visitors. These conservation engagements can involve anything from textile cleaning to treating for woodworm and are a great way to show the public how we care for our collection at Knole. Other days we may be monitoring the environmental conditions in the show rooms or polishing door brass. But one thing’s for sure, no two days are ever the same!

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Injecting a pesticide to treat for woodworm. Something we do fairly frequently!

 

Thanks for reading!

 

Listening to the Furniture

At the beginning of March this year Knole was visited by Nigel Blades, the Preventive Conservation Advisor for the National Trust and a team of researchers from the Polish Academy of Sciences in Krakow. They were here to install some pioneering technology in the world of heritage sciences. With the help of furniture conservator John Hartley they have attached acoustic emission (AE) monitors to some of the most important objects in the house. The basic principal of these sensors is to listen for otherwise imperceptible noises emanating from objects as they react to the changing environment around them. 

Some of the sensors have been attached simply by wedging plastazote (an inert spongy material) into a convenient crevice, whereas others required gluing by a furniture conservator (although a hairdryer was needed to speed the drying process in the freezing temperatures at Knole!). Using a combination of gluing, wedging, and tying all of the monitors have been successfully attached.  

John Hartley preparing the sensor mount (left) and the finished sensor (right).

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Sensor wedged with plastazote into a convenient gap in the 17th century Gole table.

 

These monitors are designed to pick up the tiniest cracks and pops emitted by the furniture as it reacts to the environment around it. The relative humidity (RH) in the Showrooms of Knole can cause certain materials such as wood and metal to expand and contract as it fluctuates. It is impossible to tell how much the objects themselves are moving with the naked eye and so this AE method has been developed to help us better understand what seasonal variations in RH are doing to our collection. The sounds the equipment are monitoring for are so tiny they couldn’t hope to be heard without these specialist sensors. 

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The monitoring equipment in the Spangled  Bedroom

 

Sensors have been attached to 4 objects in the house; the Gole table and a torchere in the Great Store and the Jensen table and a torchere in the Spangled Bedroom. Selecting these objects allows the researchers to compare the effects on similar objects in varying conditions. The Spangled Bedroom currently has no environmental control at all. This means the the temperature and relative humidity change with the weather conditions outside with no human intervention. The Gole table in the Great Store however is subject to environmental control which keeps the relative humidity below 65% at all times. 

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The full setup on the Jensen torchere in the Spangled Bedroom.

 

The ideal conditions for a mixed material collection in the National Trust is between 40% and 65% although this is not always possible. Part of our long term conservation project at Knole is to try and install environmental control throughout the Showrooms so that the RH can be carefully controlled.  

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Every room has an environmental monitoring device like this. The Spangled Bedroom one has been placed behind the table and is recording temperature and RH every 15 minutes.

 

The AE project will run for a full year from now and it will allow us to understand and better manage the change from an uncontrolled to an RH-controlled collection. The sensors and laptops will be left in their current positions permanently and will be checked remotely from Poland once a week to make sure everything continues to function properly. 

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Furniture conservator John Hartley (left) and researcher Marcin Strojecki (right) discuss the placement of an AE monitor on the Gole torchere.

 

It was fascinating to see researchers and conservators of different disciplines come together at Knole to put this project together. Hopefully it will yield some interesting results!

 

Thanks go to Nigel Blades and everyone on the AE project team for providing the information and pictures in this weeks blog.

 

Tamping

As we prepare to reopen the house tomorrow we have our last preparations to take care of. As well as the more glamorous elements of conservation at Knole are the little jobs that people often forget about.  

One such job that gets done a couple of times a year is tamping mats. This is a great stress reliever as things get more and more hectic around here as it involves a lot of jumping up and down using lots of energy! 

The basic goal of tamping is to shake loose the excess dirt and dust that builds up over the course of a year in our mats. We have a number of coconut mats around the house that collect dust from visitors feet. Our biggest mats are on the loggia in front of the main entrance and exit to the house.

 

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Melinda jumping up and down on the Loggia.

 

These huge mats need a really good beating to make sure all of the dust and dirt is cleared out. You can see here just how much dust gets collected from just one mat! 

We flip the mats upside down and jump up and down and stamp and beat until dust and dirt is all loosened and fallen onto the ground. This is the result of jumping up and down and beating the mat once:

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And twice:

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And a final third time:

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And remember this is all from just one mat!

 

 The dust that comes out is incredibly fine, more like sand, thanks to the numbers of feet that repeatedly pound over it every day. You may think that this much dust really should be dealt with on a daily basis but we vacuum these mats every single day! This is why it’s so important to vacuum throughout the house and to try and make sure people have clean feet when they come inside.

 Hopefully they’re now ready to take on another Sahara’s worth of dust!