A few years ago, my friends made me a painting for my birthday.
It's not super artistic but I like it a lot.
But I must have done something wrong because the colours are all faded.
I went and asked a restorer of works of art from the Musée d'Art Contemporain in Montreal
why the colours of my painting have faded so much.
In general, colours fade
because of light exposure.
Either daylight or electric lighting
depending on where you keep your painting.
I've moved it around a lot but I tend to keep it here, by the window,
exposed both to daylight and to electric light.
I don't know what else I could have done.
Keeping it away from intense lighting is important,
especially if it was done with felt-tip pens
whose ink is very sensitive to light.
So keeping it at a low lux,
a low light intensity,
and away from direct sunlight.
Sunlight is usually the strongest
because it includes the most light rays
from infrared to ultraviolet rays.
All of those rays react with organic matter
including the pigments that make up the colours.
This process isn't exclusive to sunlight, it also happens with incandescent light
with regular or halogen bulbs
which also emit a certain amount of light
so you always have to keep a low light level.
Of course, cheap felt-tip pens weren't the best choice
for the painting to last.
But that didn't really matter at the time.
However, I'm curious as to how light affects colours.
What mechanisms lead them to fade?
Light is made up of very fast particles
that turn into waves
so those particles carry a lot of energy.
When that energy interacts with matter,
it excites matter so much that it knocks electrons away from their molecules
and that's how physical and chemical changes can occur
with colours.
Every pigment has its own degree of sensitivity
so not all types of light have the same effects on all pigments.
Red pigments are generally more sensitive to light than others
though that varies within red pigments, too.
Pigments derived from plants are usually
extra sensitive to light exposure.
Interesting, so not only does light affect colours
but the origin of the pigments also matters.
We often forget it but colours can come from all kinds of sources.
They can come from plants or from animals,
there's a red pigment we get from crushed insects.
Sometimes we use human matter
Blood for example, or something else
And they are particularly sensitive to light
so blood stains, or if blood is used as an ink
it will darken or becomes lighter with time
So we light it at very low intensity and for a short period of time
Colours can also come from minerals.
That's often the case for earthy colours,
sienna, greens, colours used for shadowing etc.
They come from minerals, from crushed stones.
There's also coal for the blacks, or soot.
There are several kinds of burning residue for different shades of black.
There's also several types of binders used to fix colours.
There's acrylic,
oil,
or watercolour.
It all depends on what binder fixes the colour,
because a binder creates a kind of filter.
The pigments are captured by the binder,
so the light reaches the binder first before it gets to the colours.
Everything went wrong with my painting:
I have the worst ink and I didn't varnish it to protect it and extend its lifetime.
I'm starting to grasp the extent to which
the management of light on works of art is a science.
We can calculate how much lux we can subject a certain piece to per year
for a certain type of artwork.
If we want to keep it for 1,000 years,
we know we can't go over a certain amount of lux every year.
We calculate it like that.
For paintings, we go until 150 to 175 lux,
sometimes more depending on the medium.
For fragile artwork made on paper, a watercolour for instance,
or colour photography,
we display them under 50 lux.
They always require a lower light intensity.
That's why some museums have very dark rooms
for smaller artworks or ones that are kept in drawers
to keep them away from the light as much as possible.
That helps us showcase them longer.
That means that all the paintings we get to see
have a limited life span.
I'd never thought about that.
The art we see in today's museums won't necessarily be
available for all future generations.
Now I see how important it is to digitalize our artwork.
I didn't expect my picture to last forever,
but what about the Mona Lisa?
The Mona Lisa is so important and so popular
that it's one of the best looked-after paintings in the world.
It is kept under glass
so the glass itself likely protects it
from ultraviolet and infrared light;
the climate under the glass is also under control
in order to preserve the materials and colours
for as long as possible.
That painting was done on a wooden panel,
and Leonardo had a relatively good painting technique
that's pretty consistent for a wooden panel.
It's also varnished,
so it's a rather stable painting
as opposed to a paper artwork.
The Mona Lisa isn't leaving us anytime soon,
although there's some concerns about a crack in the wood.
I'll leave a few links below if you want to learn more about that.
There's even a paper that studies a prediction of the extention of the crack.
Physics really is applied everywhere.
To sum up, light damages paintings
but if we don't like them, we can't see them,
so we need to come up with some tricks
to both see them and preserve them.
We can build glass cases that already include a filter,
or we can stick filters directly onto normal glass.
They're invisible but they filter out light rays.
If we can't do that, we'll use blinds or curtains.
We'll display less sensitive pieces in front of the windows.
I discuss exhibit projects with the museum curator
and see that for instance, a photography exhibit will run for 8 months
so we'll adjust the lux levels to match that
but afterwards we'll leave it to rest for a few years
to compensate the "wear and tear".
We use LEDs or halogen lighting here
but we adapt to new lighting technologies.
We always prefer lights that aren't tainted
so that doesn't change the look of the paintings.
We try to recreate daylight as closely as possible.
It's also an aesthetic choice.
Some curators like harsher, stronger lights
so the lighting designer will adjust to the taste of the curator
and the atmosphere they want to create.
Sometimes, artists have specific requirements
so they may ask for a dramatic kind of lighting.
That'd be lighting that uses beams
to isolate the artwork and create a frame around it.
You can also give a more intimate feel to a piece
with softer lighting,
or you light the whole room with white light
and it feels big, you want to see everything,
it feels more spacious.
So we play with the perceptions of space, and intimacy
we want to create with the artwork.
What about flash photography,
is it really so much worse than daylight
for it to be prohibited everywhere?
The old flash cameras used to have harmful lightbulbs.
Nowadays they use LEDs which are less harmful.
Some tests were done where flash photography
was done repeatedly on some artwork
for hours and hours,
and although you'd think it really damages the artwork,
but that hasn't really been proven.
It's a precautionary measure.
It's also a case of not bothering the other visitors.
So if you're an artist and want your work to resist the test of time,
avoid blood-based artwork on paper
or light will destroy it.
There's actually many more parameters that museums take into account,
like temperature, humidity or even the safety of the artwork and the public.
We don't always realize how present science is in our daily lives - even in art.
Yet science is also, in some way, artistic.
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On Scilabus Plus, the second channel,
you'll find another very short video about the restorer's lab.
I'm pretty jealous of her working conditions!
I'd like to try something else with you.
I'd like this relationship to be more interactive between you and me,
so at the end of each video, for 2-3min,
I'd like to go over the previous video
and especially to answer your questions (if I can answer them)
So you can leave your comments
and I'll select some questions
to address in the next video.
So let's start with the last video
which was about the oldest animal on Earth:
a clam!
2 questions kept coming up.
The first one questioned the possibility to use carbon 14
to find out the clam's age.
You guys said, quite rightfully,
that carbon 14 datation requires for the animal to be dead
since carbon only starts decaying after the animal's death.
That's how we date stuff.
At best we'd get its death date but not its birth date.
which is useless when you're looking for its age,
I totally agree with that.
But I was mainly referring to the shell
which is not alive
so if we date the shell, don't we get the clam's age?
I might have extrapolated too much on that
so if you have more info about carbon 14 datation of shells,
you know where to find me, I'll read your comments.
The second point was about the longevity of the clam
and how there's a jellyfish that can live a lot longer.
Now that's true, but the jellyfish are cheating.
They live in a way that prevents them from aging:
it's a constant cellular renewal process.
The clam's cellular mechanism is similar to ours
but without showing signs of aging.
So they're completely different mechanisms
which land them into two different categories.
Enrique, the researcher I intervewed, answered many of your questions
and often provided sources for them.
So if you're curious, head back to the comments section of the last video.
all the info will be there.
I hope you liked this video,
and I'll see you next time!
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