Making paint with minerals

Student Sheet

In this practical I will be:

• Creating egg tempera paints and oil paints from different types of minerals.

• Evaluating the different paints, looking at various aspects, including: 

  • what colours different minerals make; 

  • how easy the different types of paint are to use;

  • and which paints give the highest quality finish on different surfaces.

Introduction:

Whilst polishing your spear with plant oil, you accidentally drop a couple drops onto some powdered charcoal by the fire pit. You notice that an interesting solution is made with the charcoal, and you wonder if you can paint with this solution. 

And if you can make paint using the mineral charcoal, then maybe you can make paints from other different minerals, binders and extenders. You decide to investigate further…

Equipment:

• Spatula
• Linseed oil 
• 1 egg 
• Ethanol
• Water
• 2 plastic pipettes
• 2 paintbrushes
• 250 ml beaker 
• A4 paper
• Piece of MDF (or white tile)
• Small prepared canvas 5 cm by 5 cm (or similar)

Access to:

• Copper(II) carbonate 
• Calcium carbonate 
• Iron(III) oxide
• Carbon powder
• Ethanol
• Disposable plastic cups or Petri dish
• Washing up liquid
• Paper towelling
• Disposable apron
• Disposable gloves
• Newspapers to cover the work area
• Pestle and mortar (if using lumps of minerals)

Hazard Warnings:

• Wear safety glasses. 
• Wear disposable gloves.
• Wear dust masks (if using lumps of minerals)
• Ethanol – Highly flammable and harmful
• Copper(II) carbonate – Toxic if swallowed and irritant 
• Calcium carbonate – Low hazard
• Iron(III) oxide – Low hazard
• Carbon powder – Irritant

Method:

Preparation of the pigment

1. If the pigment is already finely ground skip to the questions. If you have large lumps of pigment carefully measure out your pigment into the mortar. Cover the mortar with a sheet of paper or put it inside a plastic bag and grind very gently until you have a fine powder. (You don’t want to raise too much dust, as the dust is harmful.)

Use the spatula to bring the fine pigment powder into a small pile. Leave it in the mortar.

• Why is the pigment ground to a fine powder?
• What is the chemical difference between carbon and the other pigments?
• Describe and compare the appearance of the lump of pigment and the fine powder pigment.
• What are the differences?
• Why do think there is a difference?

Making the paint from fine pigment particles

2. Separate the yolk of an egg from the white. Break the egg and place the egg into an egg yolk separator to separate the yolk of the egg from  the white. Alternatively, break the egg and carefully hold all the egg liquid in one half of the shell, then pass the yolk between the two halves of the shell letting the thick transparent ‘white’ flow off into a 100 cm³ beaker or plastic cup. This should leave the yolk in one half of the eggshell. 
3. Drop the yolk into another 100 cm³ beaker or plastic cup; add about 5 cm³ of water, and mix thoroughly with the yolk to form a paste.
4. Using the spatula take about 20 g of the pigment from the mortar and place in a pile in a Petri dish. Put 3 spatulas of copper(II) carbonate (or any of the pigments provided) into each of two disposable plastic cups.
5. Repeat step 4 using the same pigment but put into a second Petri dish or pair of plastic cups.
6. Push a small dent in each pile of pigment.
7. Using an eyedropper or plastic pipette drop a small quantity of yolk and water mixture into the dent in one pigment pile.
8. Repeat the above step but this time drop a small quantity of oil into the same colour pigment in the other Petri dish or plastic cup.
9. Use the cotton bud or spatula to very gently thoroughly mix the binder with the pigment to form a thick paste.
10. If the pigment is too stiff, add more of the egg binder or some of the distilled water as the extender to thin it. If you are using oil as the binder add more oil or alcohol as the extender. (Plant sap or saliva was used by early artists because it would mix easily with oils or fats and would be stickier.)

Ideally you want a not-too-thick paste. Too much thinning can make the pigment harder to paint with, and it may run off the slab.

11. It may be that certain pigments just will not wet. If this happens add a drop or two of ethanol (care, ethanol is inflammable) to the pigment to help the water moisten it
12. Stir round in small circles, and every now and then scrape the pigment back together into a heap.
13. When the pigment is smooth, cover it.
14. When all the groups have finished making their paint sample then move onto the next step.
    • Describe the appearance of the egg yolk and the egg white.
    • Was making the paint paste easy?
    • Did adding more binder make a difference to the colour and was it different from the addition of the extender. What was the difference?
    • Compare the colour of your paints with the lump and powder pigment. Is there any difference?
    • What are the differences?
    • What do you think has caused the differences if there are any?

Using the paint

15. Now use a paintbrush and the paints to paint a shape on to a piece of white paper.
16. Repeat using the MDF board and the prepared canvas. 
17. Rinse the paintbrushes before repeating with the other paints that you have made.
    • Describe the appearance of the paint before painting.
    • Was it easy to paint on each surface?
    • Describe the appearance of the dry paint on your painting.
    • Was it glossy, dull, bright, smooth, or rough?

Evaluate the paints by completing the following table.

Criteria/ Pigment

Malachite + Water or Egg Yolk

or Linseed oil

Haematite + Water or Egg Yolk

or Linseed oil

Carbon + Water or Egg Yolk

or Linseed oil

 Going further:

• Using a paintbrush, paint with each different paint type and colour a design on to a piece of MDF or cloth. Note how easy or difficult the paint is to spread. Does it cover easily, does it smear or does it require a second coat?
• Note how it dries, quickly or slowly? Think about the implications for time to paint.
• Make an evaluation of which binder you think is best.
• Identify your criteria for your judgement.
• Can the criteria be standard if the surfaces are different materials and have different dimensions? Explain your answer.
• Explain why paint seems to have had such a complex history.

Theory:

In the fifteenth and sixteenth centuries, there was a gradual movement from tempera paints to oil paints as the primary medium. This movement began in northern Europe for the following reasons:

• Egg tempera paints: dried quickly, less colour saturation, and low transparency;
• Oil paints: dried more slowly (easier to work with), greater colour saturation, and increased transparency.

Egg tempera paint is made by mixing pigments with an egg yolk binder. This mixture is thinned with water, acting as the extender. Egg yolk dries fast and forms a hard film and that is one of the keys to a good paint. The other is the choice of mineral pigment, its depth and permanence of colour. The problem is that drying time is variable and is affected by environmental conditions.

Water and egg yolk mix with each other due to the presence of lecithin which allows an emulsion to be formed. This is due to the formation of weak hydrogen bonds which makes the yolk water soluble. The oil substances in the egg yolk make the paint flexible. When the egg tempera paint dries the water first evaporates leaving the pigment - yolk mixture glued to the surface and protected by a protein skin. Overtime this mixture cures or hardens.

Olive oil and linseed oil became the oil medium during the Renaissance. Oil paintings do not really dry hence the ‘drying’ time for olive oil is excessively long. The oil is generally mixed with the pigment and an extender such as alcohol, white spirit or turpentine. These allow the paint to be used easily and they will evaporate as the paint is applied. This leaves an oily pigment paste on the surface.

Then a different process takes over. The oily pigment paste begins to react with the oxygen in the air. This reaction is known as oxidation and it causes the oily pigment paste to harden. At the same time some of the oil molecules form cross links or weak bonds resulting in a plastic. These sets of reactions continue over time leading to some changes in the depth of colour on some paintings.

Oil painting as we know it today emerged from much experimentation with egg-oil tempera painting media by Northern European artists during the 15th century. Flemish painter Jan van Eyck is credited with developing a stable medium based on linseed oil and his painting Giovanni Arnolfini and his Wife, which hangs in the National Gallery in London, is considered one of the first to employ a linseed oil paint preparation method that is still used today.

Teacher and Technician Sheet

In this practical students will:

• Create egg tempera paints and oil paints from different types of minerals.

• Evaluate the different paints, looking at various aspects, including: 

  • what colours different minerals make; 

  • how easy the different types of paint are to use; 

  • and which paints give the highest quality finish on different surfaces.

Introduction:

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

The science of paint was once the domain of artists who developed and made their own paints, but as time went on it became a manufacturing industry with clear criteria for each paint type. It did not become chemistry until the 19th century. Before 1800 artists used natural minerals as pigments and lake pigments from natural dyes and some manufactured minerals.

Yet each era in art history has had its own science story. One thing that is clear the practice of making paint is very old and still works to the same principles. One book, Il Libro dell’ Arte, set out the principles of paint and paint materials making. It was written in the 15th century by the artist Cennino d’Andrea Cennini and continued in use for many years.

From the Palaeolithic Period to Early Romantic Art many of the paints were made using the same materials in the same way using natural minerals as pigments such as:

• Green = malachite (basic copper(II) carbonate CuCO3.Cu(OH)2), a mineral found in many parts of the world where copper veins have been altered by weathering and contact with rain. It was used for eye-paint in Predynastic Egypt and as paint on tombs.
• Red-brown = haematite (iron(III) oxide Fe2O3), a mineral found in many parts of the world. Ochre is clay that is coloured by varying amounts of haematite, from 20% to 70%. Red ochre contains unhydrated haematite; yellow ochre contains hydrated hematite (Fe2O3 H2O). The principal use of ochre is for tinting with a permanent colour and has been used from Palaeolithic times.
• Black = charcoal (carbon C), an element obtained when organic materials are burnt;
• White = calcite, limestone, chalk and marble, (calcium(II) carbonate CaCO3). Calcite is a mineral that makes up limestone and chalk. Limestone and chalk are sedimentary rocks found in many parts of the world. Chalk is a fine grained form of limestone. Marble is a metamorphic rock formed from limestone that has been in contact with an igneous intrusion. This heat changes the crystalline structure to form large crystal grains making it very hard. All forms are found in painting as white pigments and for other purposes. Calcite was used as a white pigment. Chalk was used with animal glue to form a ground coat (white surface for painting on) and as an extender. Marble was ground up and used in fresco painting. Marble is also a popular material for sculptures.

Each pigment is mixed with a binder such as egg yolk or oil and an extender such as water or alcohol.

(This practical is best done with groups of four pupils each pupil could chose a single mineral and make both tempera paint and an oil paint for testing. Groups allow 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, article, presentation, poster or talk.)

Curriculum range:

It links with:

• asking questions and developing a line of enquiry based on observations of the real world, alongside prior knowledge and experience;
• using appropriate techniques, apparatus, and materials during fieldwork and laboratory work, paying attention to health and safety;
• making and recording observations and measurements using a range of methods for different investigations; and evaluating the reliability of methods and suggesting possible improvements; 
• presenting observations and data using appropriate methods, including tables and graphs; 
• interpreting observations and data, including identifying patterns and using observations, measurements and data to draw conclusions; 
• presenting reasoned explanations, including explaining data in relation to predictions and hypotheses; 
• the concept of a pure substance; and
• mixtures, including dissolving. 

Hazard warnings:

• Any of the powders can be an irritant if the fine dust is breathed into the lungs.  The paint should not be put on the skin. 
• If the students are grinding the paint from large coarse lumps of mineral (this would only be appropriate with English KS4 students) then the students should cover the mortar with a large plastic bag and grind very gently until a fine powder. For English KS3 ensure the pigments are already finely ground and students can start at step 3.
• Alcohol is flammable (highly flammable and harmful) so ensure there are no naked flames in the laboratory and no other sources of ignition close to the ethanol.
• Wear gloves when handling raw eggs. Wash hands and disinfect the work area thoroughly afterwards. 
• During the paint preparation it would also be advisable for the students to wear plastic gloves and safety glasses. 
• Linseed oil left on rags or paper towels has been known to ignite spontaneously. If oil is mopped up after a spillage, dampen the rags/paper towels before bagging them for disposal.
• Ethanol (IDA) – Flammable liquid (Cat 2), Acute toxin (Cat 4 oral) specific target organ toxin on single exposure Cat 2
• Copper(II) carbonate – Toxic (Cat 3 oral) and Irritant (Cat 2 skin, eye and respiratory)
• Basic copper(II) carbonate –  Acute toxin (Cat 4 oral) and Irritant (Cat 2 skin, eye and respiratory)
• Calcium carbonate – Low hazard
• Iron(III) oxide – Low hazard
• Carbon powder – Eye irritant (Cat 2) Respiratory irritant (STOT SE3)

Equipment: 

For each group of students:

• Newspaper to cover the surface of the bench
• 1 mortar and pestle (if using lumps of minerals)
• 1 large plastic bag to cover the mortar and large enough to allow easy movement inside (if using lumps of minerals)
• 1 spatula
• 1 egg
• 1 egg yolk separator (if available)
• 1 beakers (250 cm³)
• Measuring cylinder; 10 cm³ 
• 100 g of each of the following minerals: malachite, haematite, carbon or calcium carbonate in labelled screw top bottles or containers
• 50 cm³ of each binder: linseed oil, and egg yolk (vegetable oil and craft glue could be used as substitutes for these)
• 50 cm³ of each extender: ethanol (labelled inflammable) and distilled water, in a small labelled bottle
• 2 Petri dishes or plastic cups
• 2 eye droppers or plastic pipettes
• 2 fine paint brushes
• Square of MDF measuring 12 cm by 12 cm and 0.4 cm or white tile
• 1 sheet of thick white paper
• 1 small prepared canvas 5 cm by 5 m (or substitute)
• Protective gloves, safety glasses and an apron 

Access to:

• Copper(II) carbonate
• Calcium carbonate
• Iron(III) oxide
• Carbon powder
• Disposable plastic cups
• Washing up liquid
• Paper towelling
• Disposable apron
• Disposable gloves
• Newspapers to cover the work area

Technical notes:

Using three spatulas of each chemical is an appropriate amount to start with as each of the chemicals are of different weights. For example, three spatulas of iron(III) will weigh approximately 9 g; carbon powder 6 g; calcium carbonate 11 g and copper(II) carbonate 32 g.

The small pieces of canvas can be bought from a local art shop (£5 for three, if on sale!).

Using a piece of white cotton stretched (for example, over the base of an empty ice cream tub) and held tight with a rubber band can make a surface to paint on for comparison with canvas although it is more porous than prepared canvas.

MDF can be sourced from local DIY shops or stores.

MDF can be replaced by a white tile or any other item with a similar surface. 

If necessary linseed oil could be substituted by any cooking oil and craft glue could be used instead of egg yolk and still yield good results for this practical.

Provide some washing up liquid to add to water in the glass beaker to assist with rinsing the brushes between using the different paints.

This is a messy practical so as well as providing the plastic disposable gloves and aprons it may be better to use plastic disposable cups that can simply be thrown away afterwards.

Results:

If lumps of minerals are to be used it would probably be best done as a teacher demonstration to minimise the risk of dust particles being breathed in.

This practical could be carried out with groups selecting one pigment powder each to use and sharing results instead. 

The replacement of linseed oil and egg yolk by vegetable oil and craft glue works well.

The difference between them is that when using egg yolk as the binder with the calcium carbonate (white) it produces a yellowish- cream white instead of the white produced with the glue binder. 

The vegetable oil is good while using it in the practical but it does not dry and hold the pigment in the same way as linseed oil, so the oil paint using vegetable oil was still wet after the linseed oil paint had dried.

The different pigments mix slightly differently with the binders, with calcium carbonate the easiest and carbon the least easy to mix, also with some needing more extender than others. This difference may be caused by the ability to grind some pigments (chemicals) into a smoother powder than others. Even the chemicals supplied in powder form can be seen to have a different fineness of powder from each other.

All the pigments used were easy to apply on paper, canvas and MDF. It was slightly less easy to apply to the substituted cotton for canvas but is still a reasonable comparison. 

The oil also spread a bit more on the cotton carrying more of the iron(III) oxide pigment with it in comparison to the prepared canvas.

With each of the pigments used on each of the surfaces the tempera paints applied well and dried easily. The oil paints applied well and stayed wet to varying degrees depending on the surface it was applied to. The difference in opacity is also observable.

The calcium carbonate and copper(II) carbonate were the two pigments that may rub off more easily or were more powdery to the touch when dried. Carbon and iron(III) oxide were the most durable pigments.

Overall, the students would be able to achieve the learning objectives of this practical within the lesson time.

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

Example results sheet:

Criteria / Pigment	Paper	MDF	Canvas
Malachite + Egg Yolk (and water)	Easy to apply Good colour and slight sheen Stays on paper well	Easy to apply with good colour Low sheen Slightly opaque Dries easily Can be scraped off easily when dried	Easy to apply Good colour No sheen Stays on well
or Linseed oil	Less easy to apply Good colour and is slightly opaque Oil is visible on the paper around the paint Dries slowly but once dried stays on paper well (can be rubbed off easily when still drying)	As above except high sheen did not dry and could be wiped away	As above except: high sheen
Haematite + Egg Yolk (and water)	As above but also a more solid colour	As above	Easy to apply Very good colour Low sheen Stays on well
or Linseed oil	Easy to apply Good solid colour Only very slightly opaque Slow to dry but stays on paper well once dried	As above	As above except: Colour is more red-brown than seen in the other results High sheen
Calcium carbonate + Egg yolk (and water)	Applies well and has the most noticeable colour differences. A creamy yellow white results from the egg yolk binder Less sheen apparent than the other colours Stays on paper well	As above
or Linseed oil	Still powdery, will come off easily and visible oil around the paint	As above
Carbon + Egg Yolk (and water)	Applies well with good colour depth Slight sheen Slightly gritty	As above	As above
or Linseed oil	Slightly gritty, not as smooth as the others Oil visible around the paint Stays well once dried	As above	Easy to apply Good colour High sheen Stays on well