# Paint It!

Purpose

In this unit we measure small quantities of paint accurately to produce our own colour range. We also think about the physics of colour and how our eyes see different colours.

Achievement Objectives
GM3-1: Use linear scales and whole numbers of metric units for length, area, volume and capacity, weight (mass), angle, temperature, and time.
Specific Learning Outcomes
• Accurately measure volumes up to 10 ml.
• Estimate amounts of constituent paint used in given mixtures, up to 10ml.
• Describe the effect of adding incremental amounts of white paint to an existing colour.
Description of Mathematics

In this unit students reads scales, and develop an understanding of the size of a millilitre by working with measurements. They compare volumes using phrases such as “less than” greater than” and “equal to”.

#### Associated Achievement Objective

Science, Physical World AO1: Explore, describe, and represent patterns and trends for everyday examples of physical phenomena such as movement, forces, electricity and magnetism, light, sound, waves and heat.

The concepts covered in this unit are outlined more fully in "Seeing Colours, The Spectrum, the Eye and the Brain", number 11 in the Building Science Concepts series.

The main idea covered is that the colours of objects come from their reflection and absorption of different parts of the spectrum of colours in light.

The learning opportunities in this unit can be differentiated by providing or removing support to students, by varying the task requirements. Ways to support students include:

• providing physical materials, paint and measurement tools, so students can experiment, and have real experiences of colour mixing
• explicit modelling of ways to record paint recipes, including how measurements such as millilitres (mL) and litres (L) can be written, and the symbols used in ratios
• allowing access to calculators to reduce the calculation demands for students who need that support.

Tasks can be varied in many ways including:

• manipulating the complexity of the colours students work with. For example, start with just yellow and blue as primary colours
• limiting the number of drops allowable in a paint recipe
• supporting students to organise their recipe creation as an algorithm (sequence of steps). Provide a chart of steps if necessary for some students.

As an extension, students could be encouraged to research the difference between the RYB and CMYK models of colour mixing.

The contexts for this unit can be adapted to suit the interests and cultural backgrounds of your students. Colours often have cultural sigificance. For example, green is associated with pounamu in Māori culture, Red is associated with birth, coming into being, and Papatuanuku, Earth Mother. Black represents the heavens and white the coming into light. Be sensitive to the cultural significance of colours for students in your class. In Chinese culture, red represents luck and fertility, but in some African cultures it symbolises death. Green is a sacred colour is Islamic cultures.  Ask your students what ideas they associate with different colours.

Required Resource Materials
• Acrylic paint in primary colours: red, blue, yellow and white.
• Plastic droppers or syringes to measure small amounts up to 5mL (These tools often have scales to measure in mL)
• Paint brushes
• Paper
• Samples of paint charts
Activity

#### Introduction, Session 1

1. Brainstorm students’ ideas about colour.
What can you tell me about colour and how we see it?
How is it that we are able to see colour? (light)
Why do colours appear different in different lights?
How can we create colours?
2. Explain that this week the students will become paint designers and technicians, creating their own new colour range of paints.
3. Allow the students time to experiment with mixing colours of paint to create new colours, focusing on the variety of combinations possible. Start with two colour blends of the primary colours.
4. Let students experiment with blending primary colours. Use droppers or syringes that are repeatedly cleaned to reduce waste. Use paint trays to hold small amounts of the primary colours and black art paper as the painting surface.
What will you need to record so you are able to reproduce these new colours?
Students might recognise that some record of the comparative amount of each primary colour will be useful. They might decide on a drop as a unit of amount (volume) and the use of ratio notation, e.g. 3 yellow: 1 blue. (20 drops is approximately equal to 1 millilitre).
5. Have students share some of the colours they have created and describe how they achieved the effect. Do they record the colours as ratios?
6. Discuss how colours might be altered to make them darker or lighter, more/less blue or red, etc.
7. Show the samples of paint charts.
Why do paint shops produce these charts?
If a customer chooses a colour how do the paint people make a whole can of it?
8. Look online for a video that shows how tint is added to a base in a strict recipe. Even with this precision there is always a disclaimer that colours vary slightly from the charts.
9. Discuss the need for consistency.
If customers were going to purchase our paints they would need to be the same every time.
How will we achieve this?

What units of measurement will we need to use?
10. Discuss how to use the droppers or syringes consistently, as a way to accurately measure small quantities of paint.
Are all drops the same?
What causes the drops to vary?
How might we be more consistent?
11. Outline the unit of one mL as one thousandth of a litre. Showing students a one litre container and a cylinder that has millilitre gradations will help students appreciate the small size of 1mL. A small place value cube is the volume of 1mL. A large place value cube is the volume of 1000 mL or 1 litre.
12. Ask: Suppose the recipe at the paint shop said 1 red: 3 yellow. What colour would that give?
Will all oranges made with this recipe be the same? (Maybe not, but close)
13. Allow students time to practise measuring small amounts, reinforcing the importance of being accurate and reading the scale carefully. Students can work in teams, taking the recipe of another pair and trying to reproduce exactly the same colour. (Note that wet paint changes colour as it dries. It usually lightens.)

#### Exploring, Sessions 2-4

1. Over the next few sessions have students develop 2-3 base colours and record the “secret formula” for these colours. For example, Groovy Green is made from 2.5mL of blue and 4mL of yellow. As they develop base colours they can present these in a paint chart type presentation, developing lighter hues by adding a constant amount of white and also naming these colours. For example, Avocado can be made from 2.5mL blue, 4ml yellow and 1 ml white, Apple can be made from 2.5mL blue, 4 mL yellow and 2 mL white.
2. As students work, reinforce the importance of accurate measurement. Have students reconstruct the colours others have created, using the secret formulae.
Are the colours the same? Why? Why not?
3. Discuss the new colours being created:
What new colours have we made?
Does it make a difference if the colours we mix are light or dark to start with?
If so, how are the resulting colours affected?
(Dark colours have a more pronounced effect on the final colour than light colours)
4. Explain that light is made up of lots of different colours. Most surfaces around us absorb light but not all surfaces absorb all the colours of light. What we see is the part of white light that is not absorbed by the surface. That light is reflected back into our eyes.
What colours make up white light?
What colours are reflected when we see a red object?
What colours are absorbed?

What colours are reflected when we see a blue object?
What colours are absorbed?
5. Have students calculate the formula for larger quantities of paint. For example:
If I wanted to order 2 litres of paint for my kitchen what would the secret formula be?
What if I wanted 6 litres for my dining and living area?

To scale up paint recipes students will need to convert between measures and apply multiplication. For example, Punk Purple is made with a ratio of 2 red: 3 blue : 1 white. How many millilitres of each colour are needed to make a 1 litre pot?
Since 1L = 1000 mL each part will need to be calculated as a fraction. There are 6 mLs per unit ratio, since 2 + 3 + 1 = 6. 2/6 or 1/3 of the mix is red, 3/6 or ½ is blue and 1/6 is while. The amount of each colour is:
1/3 of 1000mL = 333.33 mL, ½ of 1000mL = 500mL, 1/6 of 1000ml = 166.67 mL

#### Reflecting, Session 5

1. Present the students with a colour you have created and named, for example Awesome Orange.
2. Explain that this is one of the colours another paint company has created and they need to discover the secret formula as one of our loyal customers has requested it.
3. Allow the students time to experiment with paints to find the formula. As they work compare the results and the mixtures they have used. For example:
Why is your orange lighter/darker than Awesome Orange?
What do you need to change? Why?
What amounts of paint will you try now?
4. As a conclusion share the secret formula for Awesome Orange and have students share their finished paint charts with the group.