Infrared radiation

• Science
• Lower Secondary (Key Stage 3)

Introduction

Masterminds & Masterpieces – An interactive lesson including an experiment in which students discover how conservators use infrared radiation to examine paintings by Vincent van Gogh. The lesson is suitable for independent study, or whole-class teaching.

Instructions

General learning objectives

• Students learn what infrared radiation is
• Students get to know Vincent van Gogh
• Students see how a conservator uses infrared to examine paintings
• Students look at underdrawings in their own work using infrared

A curious and inquiring mind is vital for the preservation and conservation of art, and for science and technology in general. This lesson, part of the Masterminds & Masterpieces series, uses the interdisciplinary benefits of inquiry-based learning (experimentation, testing, looking, comparing etc.). Masterminds & Masterpieces is a collaborative project of the Van Gogh Museum and ASML.

Link to curriculum

- This lessons ties in with the subjects physics and science.

Equipment needed for experiment

• TV
• Remote control
• Drawing materials
• Transparent and non-transparent things, such as toothpaste, a rubbish bag, heat-resistant foil, a piece of glass or plastic.

Variation

• This lesson can be combined with the lessons on UV – Van Gogh’s enemy/friend, and with the lesson on x-rays.
• The different elements of the lesson can be used as separate assignments at different times.

Examining Van Gogh’s paintings with infrared radiation

Infrared radiation

What are you going to learn during this lesson?

During this lesson you will learn what infrared is, what a conservator does, what layers you can find in a painting, and who Vincent van Gogh was. You will then learn how conservators use infrared light to examine a painting. Then you will do an experiment. 

What’s happening here?

Conservator Oda is getting Vincent’s painting Horse Chestnut Tree in Blossom ready for an infrared reflectogram, a technique that uses reflection of infrared radiation and other processes.

What does this person’s job involve?

This person is a conservator-restorer. She examines and takes care of old objects, and repairs any damage. Here, she is working on a painting by Vincent.

One of the jobs of a museum is to study its collection and keep it in good condition for the future. Conservators play an important role in this. 

Who was Vincent van Gogh?

Vincent van Gogh

- lived from 1853 to 1890;

- grew up in the Netherlands;

- lived in four countries (Netherlands, Britain, Belgium and France);

- decided to be an artist when he was 27

- made almost 900 paintings, over 1000 drawings and wrote hundreds of letters

- was not famous during his life

- is now a very famous painter

So infrared radiation is used at the museum to examine Vincent’s paintings. But what is infrared radiation? Look at the next slide. 

What is infrared radiation?

Infrared (IR) is thermal radiation. It is part of the electromagnetic spectrum. It has a wavelength between 0.78 and 1000 micrometres. You can’t see IR, but you can feel it. Every object emits IR radiation, including people, but the biggest source of infrared radiation is the sun. The higher the temperature of an object, the more IR radiation it emits. IR is divided into three regions: IR A, B and C. 

So IR is used at the museum to examine Vincent’s paintings. Watch the video on the next slide to see how we use it. Then answer the questions. 

How did Vincent make ‘Horse Chestnut Tree in Blossom’?

1. He painted it straight onto the canvas
2. He made an underdrawing before he started

Details of underdrawing

If you look carefully you can see a bit of Vincent’s underdrawing in the detail of the infrared reflectogram of Horse Chestnut Tree in Blossom. 

Drag the images of painting materials to the right categories

Lets IR through

Completely reflects IR 

Completely absorbs IR

A conservator-restorer uses IR radiation to..

1. .. find out how the layers of paint are built up
2. .. discover discoloration in the layers of paint
3. .. discover underdrawings

What interaction between IR radiation and the material is important when you are making an infrared reflectogram?

Important for IR reflectogram

Not important for IR-reflectogram

Reflection

Reduction

Emission

Permeation

Absorption

Transformation

What source emits the most IR radiation?

Are there objects in our universe that don’t emit infrared radiation?

1. Yes
2. No

experiment: infrared

Hide and find an underdrawing

Look at the theory behind the experiment

Dit heb je nodig:

You can do this test alone or with someone else. 

Look at the preparations

Experiment: infrared

In this experiment we’re going to imitate what a conservator-restorer does with infrared.

Which materials will you choose?

Which materials do you want to test? Think about what you learnt in the video about the ‘building blocks’ (chemical components) of materials.

Before you go any further.. 

What do you need?

• TV
• Remote control
• Drawing materials
• Transparent and non-transparent things, such as toothpaste, a rubbish bag, heat-resistant foil, a piece of glass or plastic.

Make a table

To keep things nice and clear, you can make a table with three columns, like Inssaf did:

• Materials
• Transparent to IR
• Transparent to the naked eye

Then you can tick the things you discover about each material. 

Research questions

Which materials reflect infrared, and which absorb it?

And are these materials transparent to the naked eye or not?

Once you know this, you can hide and find an underdrawing.

Watch the experiment

Compare what you have discovered with what Inssaf found out. Write your conclusions here.

Watch the video for an extra challenge

Answer the following slide.

Can you think of how you might set up a TV and remote control so that you can show the difference between reflection and absorption? Tip: it’s best to do this in pairs.

Some animals, like rattlesnakes, can see infrared, so they can spot their prey even in the dark.

In an infrared sauna IR is used to gradually warm up your muscles. The radiation easily passes through the skin and reaches the muscles. So IR saunas are not as hot as normal saunas, which have to get really hot to make sure that the heat on the surface (skin) passes through to the muscles underneath.

Even frogs (which are cold-blooded) emit a certain amount of infrared radiation.

Did you know..

that infrared is used for lots of things?

Now you’ve completed this lesson you know:

• what infrared radiation is
• who Vincent van Gogh was
• how conservators used infrared in their work
• that paintings are built up of several layers
• how you can discover underdrawings using infrared