Good afternoon. Thank you so much for
braving the winter weather or threat of
winter weather to join us today. My
name is Diana Warring, I am the director
of the Department of the Interior Museum
and it is my great pleasure to be
welcoming you to our ongoing lunchtime
lecture series. Each month we highlight
one of the workings of our various
bureaus here at the Department of the
Interior. This month of course we're
highlighting the work of the National
Park Service -- we have a lot of National
Park Service colleagues in the audience,
so welcome to you -- and we will be
highlighting the rather interesting
and wonderful conservation work that's
been going on at the Jefferson Memorial.
I've been passing by week by week and
watching what Justine finally says is
the the skunk stripe, hopefully it's
okay that I call it that too, but
watching it grow and watching the Jefferson Memorial be brought back
to its original white coloration.
So, Justine Bello serves as the
architectural conservator for the
National Mall and Memorial Parks where
she oversees the ongoing preservation of
a wide variety of memorials and
sculptures throughout the urban park. She
maintains extensive expertise in the
preservation of historic structures and
outdoor sculptures with an emphasis on
masonry and bronze materials.
Ms. Bello earned her master's of
science in historic preservation at
Columbia University in 2007 and prior to
joining the National Mall in 2016,
she worked as a senior conservator and
Vice President of Operations at
Conservation Solutions Incorporated, a
Washington DC-based conservation firm.
She was named a professional associate
of the American Institute of
Conservation in 2010, and please help me
in welcoming Ms. Justine Bello.
Well, thank you Diana and thank you all for being here today. Diana gave a great introduction
so we can just skip my first slide and get right to it. We have only 45 minutes or so today and
I have a lot to tell you about a park and
a memorial and bio film and lasers, so
without delay let's have at it.
So when most folks think of the Jefferson Memorial this is the image
that's in his or her head. It's proud, it's
solitary, it's gleaming white, it's iconic
and the word iconic is really no
understatement.
So, at NAMAs, and forgive me if I slip into
using the acronym, the Jefferson
Memorial is one of our three icons, along
with the Lincoln Memorial and the Washington Monument. And icon is a word that we take
really seriously. This is a word that implies a lot of meaning it has a
lot of symbolism both for us in the park
and nationwide, so the picture today is a
little bit more like what you see,
I guess that's on your right there.
The clean image is taken in 2003 and the soiled one is in 2016.
So you can see there's a really big
disconnect between the ideal and the
reality. So the question before us is how
do we get back to that ideal.
The ideal that exists originally for any
memorial, any monumental structure,
is the original design. So, the design
that we have here is from the famed
architect John Russell Pope. This is one
of several designs that were put forward.
He actually died before the memorial
could be completed, so we actually don't
even have his full rendering of what his
vision might have been, but we can get
pretty close. And so this is a really
beautifully rendered architectural
drawing of his vision for the Jefferson
Memorial, and I'm right about 1936.
So, Pope was not the first to make classical references in his design for a memorial.
The Lincoln Memorial, which precedes the
Jefferson Memorial for sure by several
decades you can see directly relates to
the Parthenon, which has Greek origins.
The Jefferson Memorial draws a lot of
references from the Pantheon, which is
Roman. So, slightly different stylistic
references, but the same sort of concept
in ideals -- giving a lot of gravitas, a lot
heft, and definitely a lot of marble.
I want to share briefly just a few
construction-era photos, just to give a
sense of what an incredible
architectural and engineering effort
this really was. In order to put the
Jefferson Memorial on axis with the
White House, land actually had to be
created within the tidal basin. So
massive foundations went in along here,
which can see being laid on left there,
for those that are familiar with this
part of town, you can actually see that's
Inlet Bridge back there, looking very lonely
on this sort of barren landscape before
everything got built up.
But we can see what was soon to come.
So, because this is a presentation and I'm
going to take huge liberties with time
travel, we're going to jump many many decades ahead. The memorial was dedicated in 1943.
And we don't actually have a lot of dedication-era photos, so we're gonna skip to 2007.
So, I'm going to click through the next
couple photos without a whole lot of
comment, but I actually would just ask you all to look at them and consider
some visual change over time.
2010
2014
2016
So, by 2016, we have a name for this
advancing dark menace and it is "biofilm."
Now, I should be very clear that the
biofilm was not first observed in 2016.
It had been noticed, certainly by various conservators, allied professionals,
park leadership several years prior and research began several
years before 2016. And I can't possibly
get into all the research that's been
done on this topic so far, but I want to
touch on just a few of the wide variety
of folks that have been involved to that
end over time. Over here we have a young
lady who was working with a
mathematician. They had a grant from the
National Science Foundation, they were
studying mathematical modeling and how
our biofilm might be related to that.
Students from the Thomas Jefferson High
School of Science and Technology in
Alexandria, Virginia, were looking at
culturing these different types of
biofilm and trying to characterize them
to understand what they feed on, what
they might respond to. Independent
researchers from the NIH were looking
at it from a microbiological perspective.
Other microbiologists from Montana State
University did a really deep dive into
some of the characterization of the
different strains of the biofilm that
might be present here.
So all of this is just to say that
defining research goals for this project
is vast. Just some of the ways that we
can generally understand it is that
different people have different goals
but we can summarize them in that
some folks are trying to characterize this
condition, some folks are trying to
understand the phenomenon and possibly
predict future behavior better based on
that, and others are trying to develop a
safe method for elimination.
And what we're talking about with the
elimination is really another way of
saying cleaning. So, why do we clean? I
want to be very clear that cleaning
should not be a foregone conclusion, it
should be something that we as resource
managers, as park representatives, should
be engaging in actively. Something that we need
to think about, and need to be able to
articulate our reasoning why we're doing so.
So some reasons for why we clean: to
promote ongoing maintenance of that
resource, to prevent deterioration of
that resource, specifically to promote
term preservation of the stone if
there's any sense that the biofilm or
the other soil agent might actually be
causing active deterioration of it. From
a curatorial perspective, to restore the
original design intent, how it looks. And
on similar lines to that, to
enhance the visitor experience, which
may or may not be negatively impacted
based on a change of its appearance.
So, as this breeze board asked, what's
that black stuff? That's a very good
question. So, let's pause here to talk a
little bit about this what this black
stuff is. And this breeze board was out on display behind the memorial for a
period of time to try to help interpret
what was going on here for the visiting
public. So despite what WTOP or the Post
might tell you, it's not slime, it's not
ooze, it's not goo, it's not just one
culprit. It's a very complex system of
microorganisms -- the word multicultural has actually been used,
which I think is kind of euphemistic, but lovely -- that are living and thriving
really on a receptive host, that being our
stone surface. That this is a
dark-colored biofilm, that's not the case
with all of them, but the dark
pigmentation is a protective mechanism.
That at the Jefferson Memorial it is
fast growing. And that it's not exclusive
to the Jefferson Memorial, either.
So some other examples just in and
around Washington DC: at the upper left
here we have the DC War Memorial, this
was actually before it was restored in
the early 2010-2012. It was, for those
that are familiar with it, it's a pretty
heavily wooded area at the time, that has
been thinned out some, but it was pretty
heavily soiled with biofilm at that time. Some headstones from Congressional
Cemetery in southeast Washington DC. The Folger Shakespeare Library, also
Washington DC. And the amphitheater at
Arlington National Cemetery, so this is
again just within a couple miles of here.
And so, just to give you some perspective
that biofilm is not new, it's not
unique to Washington DC, this is
something that when you start to look for it you will find it everywhere.
So some things that we don't yet know
about it: we don't know exactly which
strains might be present, or how many
might be present. It could change from
one location to a few feet distant at
another location. If and how the
relationships between these strains
might be changing over time, and how quickly.
Why they might have started to flourish
exactly when they did. And why they've
thrived so greatly at this location. The
Washington Monument, for example, does
have a little bit of biofilm on it, you
can actually sort of see it in this
aerial view at the top, but why so little
here when we have so much on its
neighbor not that far away?
So we talked
about cleaning a little bit, we broached
the subject of it. So if we're committing
to the idea that we're gonna be doing
cleaning, there are some standards and
guidelines that we need to be thinking
about as we approach designing a project
around it.
So, some of the resources that we have at
our disposal as professionals, for those
of us that are conservators, most of us
are members in the American Institute
for Conservation. We provide a lot of
guidance through their code of ethics,
that's something that's a living
document that's updated fairly regularly
and that we should be consulting for
some ethical guidelines.
Many folks in this room would be
familiar with the Secretary of the
Interior's Standards for Historic
Preservation, in all its various formats.
Again, these are advisory, they're not regulatory, but they do
provide a lot of sound guidance that's
very written in a very approachable
language, that's sort of palpable to a
general audience. It is widely applicable in
a lot of situations.
On a slightly more
technical level, we also have things like
the technical preservation briefs, the
first of which addresses cleaning of
historic buildings. These go into a
little bit more of a deep dive into some
specifics that practitioners might
want to be using when they're
considering how to design a project.
Again, these are all resources at the our
disposal -- not mandated but available and
worthy of consulting.
So, for our biofilm here at the Jefferson
Memorial, I wanted to talk just a little
bit about where it is, because it's not
everywhere, it is selective. So it's
located mostly on the dome in this area
sort of highlighted up here at the top,
some at the various cornice levels as
you step down, and then there's a pretty
clean swath across where all the columns
and column capitals are, and then it
starts to concentrate again as you get
towards the bottom -- some of the stepped
areas and the cornice of the villa or
terrace level. So we see it largely on
surfaces that tend to be carved and/or
projecting and/or might be the likeliest
to hold moisture for some extended
period of time.
I'll also comment certainly there is a
fair amount of vegetation around the
ground level, which you don't really get
the best sense of from this photo,
but that certainly is playing into some
of the phenomenon that we have there as well.
For just a little bit more of a detailed
view up at the roof level, you can really
see that when we talk about the roof
it's not even just the whole roof, it's
really the dome. You can see that just
below this very heavily soiled dome,
there's actually quite a very clean area
of this sort of drum wall. It's being
very clean down here in contrast to this.
Again, you have a soil cornice, then
fairly unsoiled roof surfaces and this
only picks up again at the portico edge there.
So in a lot of ways this effort
functionally kicked off in August 2016.
As I said, a lot of attention was paid to
it prior to that, but that is when a lot
of things started to coalesce that gave
this particular project a boost and kind
of lift off the ground. And there are
definitely lot of caveats to this.
So, some initial cleaning tests were
performed on site that month using a
variety of different cleaning methods -- 
some detergents, some water-based, some
biocidal, some using laser technology. and
this information was presented to the
public acknowledging that we didn't have
an answer at that time but that we were
exploring a lot of different options.
In the wake of making this information available,
we received hundreds of pieces
of contact from the public, lots of
interest was generated about this
subject. So that came in the form of
people providing samples, chemicals that
they suggest that we try, or providing
product data, sometimes recommending a new technique or
technology that we hadn't even heard of
before. So there was a vast amount of
information that we collected. We sorted
through all of it, every single one was
reviewed, documented, organized, pros and
cons looked at for all of them, and a lot
of detail sussed through to try to be able
to compare apples and oranges across a
very very very broad spectrum
So I don't think I'm giving a whole lot
away if I jump to the punchline that's
just that we did end up choosing
laser, and I'll get into why we chose it
a little bit later, but as you know from
the title that's where this talk is
heading. So, I want to get right to the
meat of it, because I think this is sort
of the most novel information for a lot
of folks in this audience today.
So, I want to talk about first, just lay some
ground rules out there about what laser
cleaning is not. Lasers that we're
talking about do not look like this,
they do not look like this, they definitely do
not look like this. So we'll just get that out
of the way right now, not even close.
So what do they look like?
Well, there's a variety. So to say there's one type of laser capable of doing
this work would not be accurate, there's
actually a variety of different types of
lasers out there in common practice
right now in the conservation field.
One type was used for this project but there are others that are being used all
across the world and, you know, around the
United States right now. So any one of
these could have done the job. They all
have slightly different pros and cons
and operate in slightly different ways,
but I just want to make you all aware
that there is a variety available, so
when you hear 'laser' don't think just one
laser, there's a big range of options out
there.
So, laser cleaning. What is it
even doing, how does this process even work?
And this is a highly technical
topic that we're just gonna do the
faintest skim on, but essentially this
non-visible light ablates the dirt.
That's the term that's used for this type of cleaning.
It's most effective to remove dark colored soiling
from a light colored substrate, that's the
surface underneath, such as dark soiling
on a white marble like we have here.
The light is absorbed by that dark soiling,
causing it to ablate. It's reflected back
by that light stone that's underneath. In
some ways, when managed properly this can
actually really be a very safe and
self-limiting process, because once that
dark material is gone it's not gonna
want to proceed cleaning further.
There are some exceptions to that, but that's with general principle.
Water misting can sometimes be used to augment
the cleaning effect of the laser.
This works in two different ways -- this is
not to conjure up images of full water
cleaning or pressure washers or hoses or
giant water systems being used, we're
talking about just tiny mist spray
bottles -- but sometimes a spritz of water
will actually act as a lens and
actually sort of focus the light and
change its properties. It can also redirect
it, you know, so light's going to want
to travel in a straight path. Having that
little lens can get it into pores that
it might not get to otherwise. Also, when
the light hits that tiny droplet of
water it can turn it to steam
immediately, so you actually have a steam
cleaning effects as well. So there are a
couple bonuses there.
And on any one of these units,
depending on whichever one you select,
there are many variables that can be
fine-tuned to achieve the desired
results. These are highly sophisticated
instruments that should only be used by
highly trained operators.
So although 'laser cleaning' in common
parlance is not totally familiar to many,
it does have a pretty well established
track record in conservation now some
of the earliest work was done in
Florence and in Venice in the 1970s,
1980s, starting on smaller scales like
this, some statuary, and certainly scaling up and doing some architectural surfaces as well.
But the decades since it's been
successfully scaled up to buildings as
large as West Block of Parliament in
Canada, showing that this is not just a
technology that's limited to a museum
bench, that it actually can be
successfully brought out into the field --
with many, many logistics invariables
to be negotiated for sure. But that it
is a scalable technology.
It's actually so widely used that there's a conference every couple of years specifically
dedicated to lasers in the conservation
of artwork, so this is just to say that
there are quite a lot of people out
there doing good research and good work
to this end. It's being disseminated
through vehicles like this.
So just a few other examples of laser
cleaning that's been done on comparables
at buildings in DC: the US Capitol, it's been
done at the Supreme Court of the
United States as well, Philadelphia City Hall, Cleopatra's Needle
in New York -- it's the Egyptian obelisk
that was brought there in the 19th
century -- again, the West Block in Canada and, a variety of sculptures or architectural
services really around the country.
So some of the advantages of laser cleaning,
and these were the types of things that were very compelling to the park in making
their decision to go this route, so there
are no chemicals that are used. Certainly
that's advantageous to the building, it's
advantageous to protect the operators,
those that have to normally be
applying them, certainly there's
advantages to the natural environment as
well. So there's nothing released, there's
nothing to be contained, whether its
water or effluent or abrasive blasting
media, none of that has to be factored in.
The only media that it consumes
really are electricity and it emits light,
so again there's no consumption of
materials there in the traditional
sense, as well. It is, well again when
used in the hands of a safe operator, it
is very safe for use on stone. Again,
there's no chance of using harsh
chemicals or abrasive media, we don't
have residue issues, and the run off
is really a significant issue,
particularly in a location such as that
of the Jefferson, which has a tidal basin
right around it. It's something that we were
very very mindful of.
Another thing that's very helpful in
terms of laser cleaning is that the
results are immediately visible -- that's
not always the case with other cleaning
methods. And there are variety of reasons
why we clean in all types of different
methods. Some of them take, some of them
have what's called a very
long dwell time -- you have to leave a
chemical or a poultice or other material
on the surface for a certain period of
time, and even then you might have to
repeat it multiple times until you
achieve the the desired result.
One of the advantages of laser cleaning is
really right away you know what you're
getting, so you get that sort of
immediate feedback, which is really
helpful in terms of decision making and
understanding the level of clean that
you can actually achieve.
So when thinking about this as a project, some of
the questions that I was asking myself
about how this is all going to play out
were some of these things -- I'm just going
to kind of go through really quickly and
we'll circle back to later -- so will laser
actually achieve a visible and
historically appropriate level of clean,
can this technology really successfully
be scaled at this site, can the challenging logistics of this site be
successfully negotiated, will the
resource the memorial itself be
protected throughout the process, will
the people, the contractors, Park Service
staff, visitors, Park Police, be protected
throughout the process, will our natural
resources be protected throughout the
process? So there are a lot of things
that we're sort of puzzling through all
of our heads as this was getting going.
Now in order to keep this project
manageable and useful towards future
planning,
no-one undertook the idea that we would
be able to clean the entire dome in the
first shot. So we bit off a manageable
chunk, that was sort of conceived as a
test cleaning, something that would be
very useful for guiding future efforts
and helpful in terms of understanding
those some of those logistics, some of
the technical issues, and giving a very
solid foundation of work to come.
So out of a dome that's approximately
10,000 square feet, we identified a 1,000
square foot chunk that would be cleaned
as part of this -- kind of a pie slice, if
you can imagine it, down from an
aerial view of the dome. A very specific
scaffold had to be conceived, which was sort of a challenge. This was put out to bid
in spring of last year and was awarded
in June, and the first boots on the
ground arrived in late August, with work
really beginning in earnest in September.
So you can see a view looking down from
the from the scaffold which was quite an
adventure of navigating on daily basis and
where I spent a lot of time over those
couple weeks. You can see it sort of
climbing up, precariously up the side
there, kind of like an interesting
caterpillar or something just sort of
peeking out of the top there.
So, the laser unit in action -- what does
this all actually look like in the field?
So it's a lot more discreet then you
might actually think. So the laser unit
itself is here, this fairly benign
looking box. There is a fiber-optic cable
that's attached to it, that gives some
play to the operator about where he or
she can move. It's connected to the end
effector, where the light is actually
released -- this is what the operator
actually controls, there is a trigger
that has some safety functions on that
as well.
So this is one of our operators in
action. There were normally two lasers
that were being used concurrently, on
some days there was a third. So really one
of the limiting resources in this
project, is the availability of lasers.
It's not, well if this were just a normal
water cleaning project or chemical
cleaning project, you could scale up in
terms of people and in terms of
materials -- the resources there are really
not unlimited really, but here our
resources are fairly limited. But we saw
right away that we were getting the
cleaning results that we were going for.
It's actually very very hard to see in
this photo. I mentioned before, 
the laser puts out invisible light, so
what you're actually seeing, when you see
it at all, is a little ring of plasma
on the stone surface. There's just the
tiniest little hint of it there
in that blue box. And I'll get a little bit more of a close up in this one, you can see
it a little bit better there. Again, I
mentioned that there are different
lasers that operate in different ways,
and in some lasers the beam of light
tracks back and forth in sort of
a line, so you end up with a cleaning
swath that could be anywhere from an inch
to three inches thick. You know, not
dissimilar from that of a pressure
washer wand, if that's something that
you're familiar with. This one in
particular actually goes in a circle, so
that's about the size of a silver dollar
or so. But at the end of the day, it's a
silver dollar, so we basically have a
cleaning tool the size of a silver
dollar cleaning the entire dome of the
Jefferson Memorial.
But it worked! I will also
point out there are a number of safety
controls that were maintained for this
entire process. I've touched on logistics
a little bit, so obviously access is one.
The scaffold was a huge part of this and
getting personnel and equipment access
to the roof is not an easy thing. But
maintaining safety throughout the whole
process is definitely important, as well.
So, I did mention that certainly there
are no chemical fumes that have to be
sustained by these workers, nothing that
could possibly be, you know, absorbed
through skin contact, all those are great.
But there are dangers that are
associated with the use of the laser as
well, and with good planning
they're very easily managed, but they
have to be managed very strictly. So this
person here is wearing proper PPE or
personal protective equipment. You can't
really see it, but he does have
laser wavelength specific goggles on
that protect his eyes, that being the
most important thing. A laser light to
the eye will blind you immediately,
so that is the most critical aspect of
this. So there were a number of goggles
that were maintained on sight at all
times, there were check-in and checkout
procedures even for visitors, we actually
even had a doorbell on the scaffold so
you could make an audio announcement of
yourself, so no one ever got anywhere
near the laser without having verbal
confirmation that you were properly
equipped to be there in its presence.
He's also wearing a respirator just in
case there's any ablated particulate
matter that he could possibly
inhale. There are some fail-safes that
I'm highlighting here on the actual
trigger as well -- you know it's it is a
trigger operation, so when you let go
it will stop but there are a
couple other neat little tricks that
were built into this model, that again,
should it fall or should it tip over,
there were some very good fail safes
that were built in to prevent any
accidental mis-containment of the light.
And containing the light is important.
So this arrow that you see in the back is
actually pointing to a laser curtain, and
these were draped around the work area --
again they're rated for the specific
wavelength of laser that was
being used, and they contain that beam so
somebody on the other side of this would
not be impacted by that laser beam.
So this is happening in real time, so
this is the laser light being moved
around and you can actually see the dark
is disappearing right before our eyes.
Just one more time.
So in some ways you might look at this
and think, "well that's a little slow," and
I actually look at this and think, "that's
actually quite remarkable"
because it works! We know that this works
and that is the most telling thing to me
about it, is that when you have cleaned
that spot you know it's done.
There's no wondering about what the next
step is. So cleaning was achieved, again,
immediately, we had that immediate
feedback about what we were able to do
and certainly as with most things, as you
get practice and comfort both with a
site and with just operating the
different aspects of the units, you
build up a lot of speed. And so although
it took a little bit of growing and
figuring things out, this was
something that by the end of the project
we had developed quite a quite a
successful method of doing and
again, they completed the thousand square
feet in about four weeks.
So, for a little before-and-after perspective, before is
highlighting just how dark those dark
areas really were, and after showing just
how dramatically white it can be.
So again, some before and after.
So, some of the takeaways? I did want
to circle back to some of these
questions that I asked myself at the
beginning, as I was conceiving this
project, along with a lot of other folks
in the park who had a lot of very very
helpful input put towards its end. So will
laser achieve a visible historically
appropriate level of clean? Yes! Can this
technology was successfully scaled? Well
we showed that yes, it can successfully
be scaled to clean a thousand square
feet in a fairly short amount of time,
with fairly limited resources. Can the
challenging logistics, such as roof
access and equipment access, be
successfully negotiated? Yes! Will the
resource be protected throughout the
process? Yes, this was not damaging to the
stone in any way and protecting
the resources is obviously one of our
greatest concerns. Will contractors, NPS
staff, visitors be protected throughout
the process? They were, as I mentioned
that's largely a function of the safety
controls that were put into place. I do
want to also take a moment to say how
critical U.S. Park Police was in this
process, how helpful that they were in
negotiating a lot of this, but certainly
doing their job to protect all these
resources in people, as well, that we
ended up having a really great working
relationship and both got a lot out of it.
So they were really really excellent towards that end.
And will natural resources be protected
throughout the process? And indeed they
were.
So, some of our next steps from here? Well,
we don't intend to leave the stripe just
looking like this forever.
It is very compelling in this sort of
before-and-after sense, but we do fully
intend to take it the whole nine yards.
So we are working to finalize the design
for the full cleaning project.
After that we will implement it and there will also
be a large amount of documentation that
will go with that in order to help
inform future cleaning projects, as well,
and that we will be able to disseminate with other colleagues throughout the field
