Color Mixing
| Physics: | Colors of Light, Colors of Pigment |
| Grade Range: | Elementary School, Middle School |
| Format: | Hands-on |
This is a fun way for students to learn the different ways that colors can blend. This demonstration can also be used at the high school level, since it would tie nicely into an introductory lesson on the properties of light, but it would require some minor adjustments.
Materials
- Lamps with Red, Green and Blue Bulbs
- Red, Blue and Yellow Paints with Paint Brushes
- Paper
- Pencils
- Crayons
Safety Precautions
Please See the General Demonstration Safety section of the Demonstration Safety page before performing this demonstration.
Demonstration
Preparation: Set up the stations for the students to use. Have half of the stations with three colored lamps, one of each color. Have the other half of the stations with the three paints and paintbrushes. Both types of stations will have crayons, pencils and paper.
1. Have students split into groups of 3-4. Assign each group to a station, and explain that they will be mapping out the colors for light and pigment. Have each student use a pencil to draw out a Tri-Venn diagram at each station, and explain to them that the crayons will be used to color the sections of the diagram as they go.
2. Each of the group members will be recording results for their own use on their diagram pages. The groups will mix their colors in the following four ways, based on what station they are at:
| Light Mixing | Paint Mixing |
| Red + Blue | Red + Blue |
| Red + Green | Red + Yellow |
| Blue + Green | Blue + Yellow |
| Red + Blue + Green | Red + Blue + Yellow |
3. As the groups finish their first station, they can then switch with a group that had the other station. Once a group has finished both stations, they should discuss their results.
4. Ask students to think about the following questions: Why would red light and green light make yellow light? Why can't you blend colors of paint together to create white paint?
Why This Works
Light has Additive Colors, meaning that the colors you see from light become brighter shades and hues. The reason why this happens is because the light waves don't cancel each other out. Instead, they add to each other, and blend together in a way that allows the original colors to be separated out. This is why you get white light when you mix all the colors in equal amounts; white light has all colors of light in it, and you can separate any color from white light! This is also why you can't have a true "black" light, because that would simply be no light!
Pigments have Subtractive Colors, meaning the colors will become darker shades and hues as they blend together. This is because pigments and paint will absorb all the colors except the color reflected. This means they subtract from the possible colors to reflect as they blend, and the original colors cannot be separated out once you blend them. black paint absorbs all colors because it has pigments for all colors in it. White paint reflects all colors because it has no color to it, and so it cannot absorb any!
Additional Information
- Encourage students to try this demonstration at home with their parents!
- This demonstration works well with the Stroboscope Color Wheel and the Light Box.