Making a simple paint

Student Sheet

In this practical I will be:

• Learning about the general make up of paints and using key terms such as pigment, binder, extender, tempera, lake pigment and precipitation.
• Preparing egg tempera paint and a lake pigment egg tempera paint.
• Observing, and comparing and contrasting various aspects of the two paints, including, how easy are the paints to use, how do they look, and how have the paints changed over time?

Introduction:

As a prehistoric science-artist, it’s your job to create and use paint for cave paintings. Like all science-artists you want your paints to be interesting and allow you to express your art. 

You have recently heard that you can use different types of pigments in your paint, including lake pigments. However, your tribe has never used these before. In order to see how good these different pigments, and the paints they make, are you decide to carry out an experiment…   

Equipment:

• 1 egg (or substitute provided) 
• 1 pot of calcium carbonate (low hazard)
• Metal ruler or spatula
• Plastic disposable cups
• Coloured chalks
• Saucer or tile
• 2 teabags
• 2 spoons 
• 2 eye droppers or dropping pipettes
• 2 paintbrushes
• Safety spectacles

Method:

Preparing the pigment

1. Select a coloured chalk. A red, blue or green chalk will often give a good colour but it depends on the depth of colour in the coloured chalks.
2. Using the metal ruler or metal spatula scrape the side of the coloured chalk so the chalk powder falls into a pile into a plastic cup.
   • What colour did you choose?
   • Why do you think you need to make a fine powder of the chalk?

Preparing the lake pigment

3. Use the second cup to crack the egg into and save the egg shell.
4. Carefully wash out the membrane material inside the egg shell.
5. Dry the egg shell with a paper towel.
6. Put the dry egg shell onto the saucer or tile.
7. Using a metal spoon try to crush the egg shell until you have a fine powder. You may find this difficult but it illustrates the degree of difficulty early artists experienced in making their paints. Your teacher will give you some egg yolk ground in a mortar with a pestle.
8. Transfer the egg shell powder into a clean plastic cup.
9. Take the tea bags, place it them into warm water and stir taking care to not break the bag. This will probably take 5–8 minutes.
10. Use the eye dropper or dropping pipette to transfer a small amount of the tea solution into the cup with powdered egg shell or calcium carbonate until the egg shell powder (calcium carbonate) is just covered.
11. Stir the mixture with a spoon and leave to stand for 6–8 minutes.
12. Now carefully pour off the tea liquid into another cup leaving the egg shell in the cup.
13. Using a clean spoon carefully remove the wet egg shell powder.
14. Smooth the wet egg shell powder on a paper towel. Leave to dry while you prepare your binder (step 15) for 20–30 minutes.
    • Why do you think you need to make a fine powder of the egg shell?
    • Why do you think the tea bags had to be put in hot water and left for a long time?
    • What colour is the tea solution in the cup? 
    • Why do you think the coloured egg shell powder is spread out onto a paper towel?

Preparing the binder and making egg tempera paint

 If your egg yolk has already been provided for you start from step 17 instead

15. Using an egg separator separate the yolk from the white.
16. Keep the separated yolk and white in separate cups.
17. Using a clean eye dropper transfer some of the egg yolk (or egg yolk substitute a craft glue will do) the powdered chalk.
18. Use a cotton bud or spoon to stir the mixture until you have a coloured paste. If it’s too liquid-like scrape some more chalk powder into the mixture. If too thick add some egg yolk (or substitute) or a small amount of water.
19. When you have a paint paste that you think is right use a paint brush to paint a square or small picture on one half of a piece of white paper. Label it ‘egg tempura paint’.
20. Leave to dry overnight.
    • Describe the appearance of the egg yolk and the egg white. This can still be observed by the students using an egg yolk substitute if the teacher shows them with the real egg in the demo. 
    • Was making the paint paste easy?
    • Describe the appearance of the paint before painting.
    • Describe the appearance of the dry paint on your painting.
    • Was it glossy, dull, bright, smooth, or rough?

Preparing the lake pigment egg tempera paint 

21. Now take the dried egg shell or calcium carbonate you put into tea and smoothed out on to a paper towel.
22. Scrape some of this coloured egg shell powder into a clean cup.
23. Now using the eyedropper or plastic pipette again transfer some of the egg yolk (or substitute) to the coloured egg shell (calcium carbonate).
24. Stir with a clean cotton bud or spoon until you have a paint paste. Again if it’s too liquid-like scrape some more egg shell powder into the mixture. If too thick add some egg yolk or a small amount of water.
25. When you have a paint paste you think is right, use a clean paint brush to paint another square or small picture on the same piece of white paper as before. Label it ‘lake pigment tempura paint’.
26. Leave to dry overnight. 
    • Describe the dried egg shell and its colour.
    • Do you think the dried egg shell should have been crushed to make a fine powder?
    • Was making the paint paste easy?
    • Describe the appearance of the paint before painting.
    • Describe the appearance of the dry paint on your painting.
    • Was it glossy, dull, bright, smooth, or rough?
    • What for you are the differences between the two paints?

Going further:

Make more colours of the two paints by repeating the method with a different chalk. Alternatively each pupil or group could be given a different colour so as a whole class there would be a selection of different coloured paints.

If you have saved the egg white, you could try using the egg white instead of the yolk and evaluate that against the tempera and lake paint. Students will not be able to carry out this part if they have used the egg substitute.

Evaluate the different types of paint by answering the following questions:

• Are they both the same colour and hue?
• Do they both spread evenly?
• Is the colour a strong or weak one?
• Do they have to be the same thickness of paste to work?
• Are the surfaces smooth or rough?
• Do they each dry in the same time?
• Do they both work on the different surfaces such as paper, wood, plaster or cloth?

Theory:

The paint you make is egg tempera paint. It is composed of egg yolk, powdered pigment that is insoluble, and water. It is a mixture of fine solid particles suspended in a liquid.

The mixture would be called homogenous because the pigment particles remain evenly suspended and so the colour is even throughout.

The egg yolk acts as the binder or glue to stick the pigment onto the paper or other surface.

The addition of water as an extender makes the paint a usable paste that will flow and spread easily over a surface. When you buy manufactured tempera paint it is likely to contain a gum like gum Arabic rather than egg yolk.

Homemade egg tempera can only be used for a single painting session. Over time the tempera paint changes. The water evaporates, and the chemical composition of the yolk changes. The yolk protein cures, becoming thicker.

In the lake paint the dye is soluble in water and so to make this paint the brown dye from the tea is absorbed onto the calcium carbonate of the egg shell. This lake pigment is then mixed with egg yolk and water to make the paint.

Teacher and Technician Sheet

Students carrying out this practical will:

• Learn about the general make up of paints and use key terms such as pigment, binder, extender, tempera, lake pigment and precipitation.

• Prepare egg tempera paint and lake pigment egg tempera paint.

• Observe, and compare and contrast various aspects of the two paints, including, how easy are the paints to use, how do they look, and how have the paints changed over time?

Introduction:

(The topic could start with a group discussion during which teachers introduce the following ideas, especially the words in bold.)

All around us is colour. Humans have tried to use colour to create images and one of the oldest substances used to make this colour is paint. From cave paints to modern ones, the general formula has stayed the same but to understand paint we need to know what it is made of. 

Paint is a mixture consisting of:

• A pigment (a material that reflects a colour off of the surface it coats). A pigment can be any coloured material such as a mineral. Pigments can be made from a natural dye material from a plant like tea.

• The pigment is mixed with a glue substance or binder, often in water or oil.

• There is often another liquid, such as water mixed in to make the paint flow easier or make it easier to use and this is called an extender. 

One theory about the paints used by the cave painters was that the pigments were local coloured rocks mixed with a binder such as salvia, plant sap or egg yolk. It is likely that the cave painters used all three named binders, sometimes together with a single pigment.

Simple paint using a water soluble binder is known as tempera paint and this style dominated for many centuries until oil paint was developed.

The coloured material or pigment needs to be extracted. For a mineral paint this can be done by collecting soils or rocks, grinding and separating the coloured material. This is then mixed with binder and extender to make the tempera paint

For a plant dye, the coloured substance can be separated by absorbing the coloured material on to a white material, or by precipitating the soluble dye using a metallic salt. The resulting pigment is called a lake pigment. This can be mixed with the binder and extender to make tempera paint.

The precipitation method using metallic salts is generally not appropriate for younger pupils but one can achieve the same effect by using simple kitchen materials like tea and egg shells. Some people have also used coffee successfully.

Making the ground egg shell can take a bit of time even when using a pestle and mortar so this part could be carried out as a teacher demonstration. The students could be provided with a pot of calcium carbonate instead.

The process in the following practical was used for centuries to make paints.

(This practical can be done with pupils working as individuals or in groups of two. Groups of two allows for good discussion between the pupils. Teachers can use the questions set as the stimulus for discussion and the answers can be used as a group report.)

Curriculum range:

Upper primary age students and up. It links with:

• setting up simple practical enquiries, comparative and fair tests;

• reporting on findings from enquiries, including oral and written explanations, displays or presentations of results and conclusions;

• using straightforward scientific evidence to answer questions or to support their findings;

• compare and group together everyday materials on the basis of their properties, including their hardness, solubility, transparency; 

• know that some materials will dissolve in liquid to form a solution; and

• build a more systematic understanding of materials by exploring and comparing the properties of a broad range of materials. 

Hazard warnings:

Raw eggs can carry bacteria so with younger pupils use plastic gloves and they must wash their hands when they have finished.

The chalks are mainly calcium sulfate with a safe dye. Egg shells are largely calcium carbonate and are considered generally safe if clean. 

Wear safety glasses to protect eyes from any raised dust particles.

Discourage students from putting anything in their mouths. 

Craft / paper glue (egg alternative) is safe. 

Calcium carbonate is LOW HAZARD

Equipment:

(For Teacher Demo)

• Pestle and mortar (or tile/saucer and spoon)

• Disposable plastic cup 

• 1 egg

For each pupil or pairs:

• 1 egg (or pot of craft glue)1 pot of calcium carbonate (if using instead of egg shell)

• 5  paper or plastic cups

• 1 metal ruler or metal spatula

• Access to 1 box of mixed coloured chalks

• 1 saucer or tile

• 2 tea bags

• 2 disposable plastic spoons

• 1 eye dropper (or disposable plastic pipettes)

• 2 cotton buds

• 2 paper towels and filter papers

• 1 egg yolk separator

• 2 fine paint brushes 

• 1 sheet of A4 white paper

• 1 pair of disposable plastic gloves each

• Access to (hand) hot water

• Safety spectacles

Technical notes:

The teacher could demonstrate making the powdered egg shell and provide pots of calcium carbonate (low hazard), which could be labelled as ‘egg shell powder’ for the students.

If pestle and mortars are not available then it may be worth investing in a small one for the teacher to use (they can be purchased for less than £3 from some suppliers). 

Everything involving the eggs could be carried out by the teacher with the students observing. This will allow them to see the texture and colours of the egg shell and egg white and yolk, but without any of the health concerns that may be an issue with grinding egg shells and allergies, etc.

Very similar results can be achieved in this experiment whether using craft glue or egg yolk.

Hand hot water from the hot tap can be used to brew the tea and should present no hazard. 

Results:

It takes about a few minutes to produce ground egg shell using a pestle and mortar, so the teacher should start by using the bowl and spoon and then move on to ‘one made earlier’, which could be a pot of calcium carbonate labelled as ‘egg shell powder’. 

Alternatively, the calcium carbonate connection could be clearly explained and leave everything labelled as calcium carbonate rather than egg shell powder.

One egg shell provides approximately one teaspoon of ground egg shell.

A metal ruler (utensil) works best to scrape the chalk but a small plastic ruler can work as well and they are usually more readily available.

The results are comparable between the egg shell and the calcium carbonate and the students will still gain an understanding of the process of creating the tempura paint.

The difference between using ground egg shell and calcium carbonate is the coarseness of the powder. The egg shell can still be relatively gritty compared to the fineness of calcium carbonate powder.

The results are also very similar whether using egg yolk or craft glue. 

The egg yolk / coloured chalk mixture results in a slightly different colour than the glue / coloured chalk mixture due to the yellow of the egg yolk, but the gloss on the dried paint is very similar.

The egg shell and tea mixture creates a brownish / pink paint paste while the calcium carbonate and tea mixture creates a pale brown to dark cream paint paste.

It’s best to use a couple of teabags in hand hot water for the time specified to get a good colour.

Using egg white instead of egg yolk results in a transparent paler coloured paint.

This result will not be observed if craft glue is used as an egg substitute.

Overall, the egg yolk paint mixture results in a higher glaze. 

The glue is a good substitute for egg yolk. 

Calcium carbonate powder can be used for powdered egg shell.

Egg white doesn’t mix as easily with the powder as the egg yolk or glue and is more transparent when dry than egg yolk or glue. 

If necessary this practical could be adapted to use substitutes in the ways outlined above. 

The equipment needed is readily available and the learning objectives are achievable.

The drying time needed can be less than originally stated but it may need more than one lesson to cover the practical. 

The hazards are minimal assuming the required level of behaviour from students.