Tobit Curteis, conservator, historic wall paintings

I think they’re pretty unusual because they are so extensive and although they’ve been damaged and re-touched on a reasonably regular basis, they’re also one of the most complete schemes in the country. They’re earlier than an awful lot of the staircase schemes that are in the Trust. So, in terms of rarity they are very significant indeed. They’re not the finest art. If you look at court art of the period, there is a lot finer stuff. But it’s rare to have something as complete as this, both on the walls and on the timber, and the arcades.

At the moment, I’m looking at the paintings in the Great Painted Staircase. They’ve been part of a long, long programme of understanding deterioration and conservation, both preventive and controlling the damage; and treatment – stabilising, fixing, re-touching what people tend to think of as conservation treatment. They’re a complicated set of paintings. Like much of Knole, they look rather wonderful, but are not terribly well executed. There’s a lot of stage-set about this place and the paintings are not dissimilar. They’re painted on an incredibly important grand staircase which looks vast and rich and powerful, and then turns out to be made of two thin skins of plaster on rotting lathes. And that’s all that separates it from Kent.

And as a result, from day one, they have suffered, they’ve deteriorated and  they have been re-touched and patched up. And the staircase structure has been patched up, and failed again. And this cycle has just continued throughout their lives. And in recent years, it was very evident that the deterioration was becoming more serious and the only way you were going to stop it, was to deal with the building envelope, to deal with the structure which is very lightweight and insubstantial.

A project, as part of the main (Inspired by Knole) project, there was a phase which involved taking off of the outer skin of the wall, which had been replaced with cement in the past which was cracked and leaking and damaging, generally. And there was a period of some weeks when these wonderful paintings were simply exposed to the exterior because the outer skin had been peeled off the building. And you could see the thin back of the painting. And I think everyone was extremely nervous. It had been planned incredibly carefully; the contractors were extremely good, they knew what they were doing; a very complicated, a very expensive, enclosed scaffolding had been constructed. There were environmental monitoring sensors  talking through radio waves to a little box of tricks which was then talking through the cell-net system to us in our office in Cambridge, so we knew exactly what was going on. So it was all very carefully planned and controlled.

But, like most historic building problems, there are numerous variables you haven’t anticipated; there are numerous things which don’t go quite as you  expected. And it was a risky – a controlled risky – but a risky operation. And I think we all slept a lot better when the wall was put back together, and the paintings were tucked up again, at least from the back.

Most of the paintings we deal with, the painted surfaces we deal with, respond to humidity, to a lesser extent to temperature, and sometimes to light and UV radiation. These paintings aren’t particularly photo-sensitive; the light and the UV radiation isn’t a big problem but the humidity is, which is governed by temperature. So, when you cut off the outer skin of a building, you make it thermally very inefficient. You make the paintings – you put the paintings at risk of big temperature changes which causes the glues, the paint layers, and all the things they’re made out of, to expand and contract. And if it does that too much, it can’t hold together any more. And all the layers start separating out and it peels, it flakes and it all falls off. So that’s what we were watching terribly carefully; and we were also looking at the weather reports every day, as we hit an unseasonably cold period. I told you, there are variables and uncontrolled things – and it was trying to anticipate if things were going beyond an acceptable level of risk – when we actually had to say: stop, and cover it up again straightaway.

In the end, it wasn’t the case and with these sorts of projects, also, it suggests we have more control than we do! Frankly, once you have started it is very difficult to stop halfway through. You’ve got to go the whole way. So, so there was much, much careful planning beforehand.

It’s a funny thing, when we look at an historic building and we see things changing at a rate that we like, we call it ageing, or we call it patination. And when we see exactly the same thing happening at a rate that we don’t like, we call it deterioration. And it’s an entirely subjective thing. It changes from generation to generation. We’re much more fussy than our predecessors were.

So, what I’m doing is looking at the walls to see over the course of the last six to eight months, whether since that rather major intervention took place – has there been any noticeable, any recordable change-stroke-deterioration that we want to do something about.

We have got a phase of treatment coming up. Most people think of conservation not as this stuff at all, but of people with white coats and swabs and hypodermics and things.  There is a phase of that coming up when we’ll actually physically fix the paintings, glue back flakes, re-touch losses but what I’m trying to gauge today is the rate of change, the rate of deterioration since that intervention, since that happened to see if the two might be linked. So far, it’s pretty encouraging. There is a little more than there would have been otherwise, but not, not at an alarming level.

The whole phase will only be a month. It’s a minor phase of work. It’s remedial, it’s stabilisation. It’s not major, you know, cleaning entire surfaces. or re-constructing large things. It’s just a bit of TLC, to keep everything nice and stable, over the next, hopefully, decade.

But it’s constant, it’s ongoing, you’re never going to stop the deterioration here at Knole. It’s too vulnerable a structure. All you can do is slow down the rate of deterioration, and then manage the damage that does happen. So, a little bit from time to time of treatment, a lot of looking at micro-climate, conservation heating: all those things we use to try and slow the damage. Not over-selling ourselves, not trying to convince ourselves we can suddenly stop time. We’re not going to. We can just control it a little better than we used to.