In the framework of the restoration of the amphitheater, what new approach are you considering? 1b
Our work comes after some experimentations
that enabled a scientific committee to raise some questions.
As these questions were raised,
studies were undertaken that opened some avenues of inquiry.
However, none of them came up with a definitive response
because the questions are fundamentally rather complex.
I think everyone experienced the need to make a comprehensive study.
Which is what we are doing today.
And we're starting to see some elements emerge
through which the studies that were conducted have been applied a particular situation.
The diagnosis we made
is one that concerns the entire amphitheater
its outside facades, the interior of the cavea,
the wide corridors for circulating, the staircases…All of that forms an ensemble.
The conclusion of this diagnosis is that we cannot
separate too distinctly the facade from the interior of the cavea.
There's an outside block--a crown with the facade and
the tiers that are below this crown, and an inside block.
All of that houses the wide hallways for circulating within.
This ensemble should be treated as a whole,
part by part, given the scale of the monument,
then, in a second phase, the remainder of the cavea. 22b
What are the decisive factors in terms of the damage?
The first observation we made immediately
was of a very specific pathology:
sorts of large flakes had formed
and were continuing to form,
including on the stone used for previous restoration.
That's important because it's a process
specific to this stone and in this configuration.
We looked at what was happening on the amphitheater
but also on other monuments built of Barutel stone.
There's an ancient entrance in Nîmes that is built of Barutel stone
and of which all that really remains is an arch, with not much of a load to support.
So it's an arch with a light load. There's one facade that's nearly intact,
and the other that has exactly the same kinds of degradation, the pathology
we observe on much of the amphitheater.
Which is linked to its exposition to rain.
We made an overall list of all of the parts damaged
and a map that sums up all of our observations.
When we really observe on this map the location and the degree of this deterioration
we realize that the most severely damaged parts are those that are the most exposed to wind and rain
so there's an absolutely obvious correlation.
So that's for the water that comes from the exterior.
The second element, which is really new,
is that by drilling core samples at the joint lines,
which we opened up like a book
we realized that the interior of these joints
was covered with calcite brought by the movement of water
within the masonry that was pieced together with no mortar.
If the masonry had been put together with mortar, the mortar would have been a sponge
and the water wouldn't have circulated.
Here, it circulates as if it were in a karstic network.
Then from time to time there are resurgences.
It functions like a limestone plateau. 54b
What are the aggravating factors?
There's a very clear relationship with water.
Stone does not deteriorate if it is sheltered from water.
There's also a relationship with the load: the more substantial the load is, the more the stone deteriorates.
But ultimately, it's a factor that's not that important.
There's another element that comes into play, but it's role is not absolutely clear:
the susceptibility to frost.
Nîmes may well be in the South of France,
but there are quite a few days per year below freezing.
We did some freeze cycle studies
and we observed that there is deterioration, but which remains relatively reasonable.
So frost is only an aggravating factor, and not a decisive factor
because the damage is quite general,
and more or less serious according to the exposure.
If there were certain stones that were sensitive to frost and others not,
a certain type of stone would be damaged
while a whole other series of stones would not be affected by that pathology.
We focused our set of hypotheses
around a combination of causes that would lead to that pathology.
We haven't yet established in what order
the succession of factors produces the result.
We're advancing
but we haven't yet exactly reached our destination.
We know that if we block off the entrance of water from the outside
and the water running inside
we will have resolved, I believe, 90% of the problem. 79b
Are there any other factors for damage?
The laboratory that worked with us looked at these stones very attentively.
It noticed that there were stone facies
that is the appearance of the stone,
which were geologically different:
some stones contained seashells of a certain kind.
That implies different quarries
or areas in the same quarry that were different.
We're going to continue this advanced research
to see if there's a correlation between the facies of the stone
and the extent of the damage.
But those are all secondary factors.
If there were a certain type of facies that gets damaged and not the others,
we would have noticed that long ago.
It's clearly not the case.
I think that it's really a combination of factors,
which in certain conditions cause this damage. 95b
What factors have you dismissed?
Yes, there is one element, which is the constraint,
the load on the stone.
At one time, it was thought that the Barutel stone,
which is very strong and can bear a heavy load
when it is wet, the lower part for instance,
would lose 30% to 50% of its load-bearing capacity.
In the work on the first section, some stones were changed,
which exposed the beds of the stone.
On these beds of the stones, there was a kind of edge for adjustments,
and the inside part was hollowed out. So the load was concentrated on these edges.
The accumulation of all of that, along with the stone that expanded due to the effects of humidity
could explain according to some studies which concluded
that this stone
which was weakened by all of these factors
and bearing a significant load
but far from its load-bearing capacity,
that this stone would break.
But the reality we discovered
is that the margin of the bearing capacity is huge, so that can't be the explanation.
We see examples of stones bearing little weight
that are nevertheless very damaged.
There may be perhaps a correlation:
if the stone is bearing a heavy weight, it can be a bit more damaged.
However, it does not get damaged because it's bearing weight. 119b
How do you define a restoration?
We worked with an Italian restorer, Carlo Usai,
with whom we had worked at the Louvre
and on the tomb of the kings in Jerusalem.
He came to do a cleaning test,
which we could observe because it was done at the ground level.
He also performed joint sealing tests and others with mortar.
That gives a rather good idea of the spirit in which we wanted to carry out the work.
It's a technique.
But it goes beyond the technique: we're trying to manage the image.
The cleaning consists in removing the black,
but we don't remove what are called the oxalates
that is these somewhat orange traces
which are at the same place as the black traces.
We try to not to remove everything.
If you "rewhiten" all of the facades
and in Nîmes, there's lots of sun
all of the hollow parts appear to be very dark
they are accentuated by the shadows created against a white background.
We're tempted to fill in the holes that cause these shadows
and break the architectural lines.
As a result, we slide quite naturally toward increasingly significant reconstitutions.
Whereas, if we don't completely clean the facade,
it appears rather naturally
with lines that compete a bit with the architecture,
but not too much. Which means that we can leave some shadows.
We will work then on the hollow parts of the shadows,
not by filling them in, but by working with the mortars,
in a way that creates an image that it a bit "tighter" than
its current appearance that is distorted by the black and the white traces.
Our goal is to achieve something more homogeneous, while changing the minimum number of stones.
When I say minimum, it's really as few as possible. 150b
How are your actions inscribed in time?
Of course, in an ancient monument, one must feel the thickness of time.
If the restoration cancels that effect,
you remove a great amount of the value from the monument.
That is even truer when the building is 2,000 years old.
Our analysis has always taken account of time.
For instance, we tried to understand if the areas that were long protected
by the presence of houses,
which had protected the facing materials,
were more exposed to the forces of decay.
It's not completely obvious.
Or rather, was it when the outer arches were re-opened
and these areas were exposed to the rain?
We also tried to understand that.
It's similar for the lower part of the buttresses, which were buried under 1.5 m of debris.
In the photographs taken shortly after the excavation of the Arena
to its original level, we can clearly see
whether or not these stones had been severely damaged.
Apparently, they were not. Yet today, they have been replaced.
Which means that in 100 to 150 years, stones that were relatively well preserved,
because they were buried--thus protected from the cold and the wind--,
as soon as they were unearthed, they deteriorated very quickly.
So we see there is an interpretation of the pathologies over time.
And time is not counted in decades, but in centuries.