which means that I think of color in terms of light,

in terms of amounts of red, green and blue.

Someone who works with print might think of color

in terms of combining inks, cyan, magenta, yellow and black.

A physicist might think in terms of the frequencies

and wavelengths of the light,

but there is a very different way to look at it,

through the chemistry and compounds that make up colors.

Inside those buildings, the Harvard Art Museums,

is the Forbes Pigment Collection.

- The pigment collection was put together

by Edward Forbes, who was the second director of the museum.

He had been buying works of art

and in doing so he discovered that the dealers in Italy

were seeing American collectors as something of a mark.

What he decided is that if you understand what a work of art is made of,

what the original materials were that an artist used,

then you can tell original from restoration, original from fake.

And so what he did was start buying pigments

to use as standards for the analysis of works of art.

Knowing that it was visible to the public meant that I needed to make some sense

of what we have as a collection.

So what I did was take a color wheel, open it out, have yellow in the centre

and we go along one way to blue, along the other way to red,

and purple at each end.

So we have unique colors along the top,

we have duplicates of those colors,

which are chemical duplicates, but not actual color duplicates

and then underneath on the bottom shelf we have

the raw material that makes up the colors above.

In effect, what we have are the materials that make up paint next to each other

and then if people look at the galleries below,

they can actually see what artists can do with these raw materials.

If you think about iron oxide for example, hematite, but as it forms in the earth,

those slight additions that the earth adds into the hematite deposits

allow it to look slightly different,

so we have 60 different samples of hematite.

Each of those is a slightly different shade from the other.

These pigments are not used for restoration.

We use them only as standards for analyzing samples from works of art.

By analyzing the materials, we can understand

the thinking process and if the artist is no longer alive,

it's really the closest way to having an interview with the artist.

It's also great for teaching.

We can show the students how pigments change.

They not just fade, but some pigments darken.

It's like Vaseline, but 80 years old.

It doesn't last forever.

Vermillion, red lead will turn black on exposure to light.

You can see how it started.

And then other pigments like eosin, which Van Gogh used a lot,

will fade and give an entirely different impression

of what the painting was to what it looks like now.

And so for security, we don't have the public in here.

Some of the pigments are toxic, so we don't want people touching them,

playing with them.

So pigments are made of mercury,

they're made of cadmium, arsenic and so on.

The oldest white pigment is lead white.

It's made by taking lead metal, putting it into a container with vinegar.

That container is buried in cow dung,

so out of manure you get the most pure beautiful white pigment.

That's been around for hundreds and hundreds of years.

People used it as makeup.

Lead white is toxic in the way that lead is toxic.

We have mummy brown.

It has been used probably since the 17th century

and it's made up of Egyptian mummies that have been ground up into pigment.

Indian yellow is an interesting pigment.

It's made by feeding cows mango leaves only

and collecting the urine and drying the urine.

What you see on the screen depends on the limitations

of what the computer screen can depict.

So videoing them, putting them into the digital format,

doesn't replicate the color.

There is innovation and people are developing new ways to depict colors.

So for example, Mas Subramanian developed a blue pigment called YInMn Blue.

He discovered it by accident.

It's very stable and it's the first inorganic blue pigment that's been invented

for a couple of hundred years.

There's been a new black that's come onto the market,

which is Vantablack, which stands for Vertically Arranged Nano-Tube Arrays.

What you have is a forest of very tiny tubes and light will go into that.

It will bounce around inside the tubes and then get issued as heat.

It's a beautiful velvety looking surface that doesn't bounce any light back.

Chemists produce more and more pigments every year

and I think that we're going to see pigments depicting colors

that we never thought were possible.

Every day somebody is coming in here,

taking a pigment out and using it as a reference.

This was beautifully arranged when I installed it.

It took me like four months of lining everything up

and it's all a little higgledy-piggledy now,

so you can tell that we use it all the time.

It's not an historic artifact,

it's something that we rely on to do our work properly.

- My thanks to everyone at the Harvard Art Museums.

Pull down the description for more about them

and more about the pigment collection.