Colours and pigments are seen everywhere around us. Everything in the world has Colour in it.
The rainbow currently has seven Colours, but by the year 1704, rainbows were considered to have only five known Colours, which was changed by Sir Isaac Newton who added two more Colours to it – indigo and orange. This shows that the understanding of Colour is still evolving, and to your surprise, there are actually no pure Colours in a rainbow since they all mix into one continuous spectrum.
On the other hand, pigments are Colour derivatives that are derived from organic and inorganic substances. So, to understand more about the science behind Colours and pigments, read ahead.
What is a Colour?
Colour is related to electromagnetic radiation having a certain range of visible wavelengths. All of the Colours of the rainbow, including red, orange, yellow, green, blue, indigo, and violet, are included in the visible light spectrum, which is specifically the region of the electromagnetic spectrum that ranges in wavelength from 380 to 750 nanometers.
How do Colours work?
The different light wavelengths determine the Colours we perceive. For instance, a wavelength of 550 nanometers appears yellow-green, whereas wavelengths of around 680–740 nanometers seem red. Black, on the other hand, is the absence of all Colours.
Colour perception undoubtedly depends on vision. However, one can see in low light without being able to discern between Colours. Colours don’t show until there is more light present. Thus, Colour perception also requires light of a certain critical intensity. Finally, it is important to consider how the brain reacts to visual inputs. The same item may seem red to one viewer and orange to another, even under the same circumstances. The way an object interacts with light determines how Coloured it appears to be. The physics of Colour is concerned with analyzing this interplay and the variables that affect it.
What is a Pigment?
A pigment is more related to the chemistry of the Colours. A pigment is a material that has a certain Colour because it absorbs specific light wavelengths. Even though many materials have this feature, pigments with practical uses are stable at room temperature. They have high tinting strength, requiring little to no carrier or application to perceive the Colour. Depending on whether they are organic or inorganic, pigments can be categorized. Inorganic pigments could or might not include metals. Several important pigments are listed below –
- Cadmium Pigments – Cadmium Red, Cadmium Yellow, Cadmium Orange, Cadmium Green
- Chromium Pigments – Chrome Red, Chrome Green
- Cobalt Pigments – Cobalt Blue, Cobalt Violet, Cobalt Green, Cerulean Blue
- Iron Oxide Pigments – Red Ochre, Venetian Red, Oxide Red, Prussian Blue, Sanguine
- Manganese Pigment – Manganese Violet
- Mercury Pigment – Vermillion
- Lead Pigments – Red Lead, Lead White, Naples Yellow, Lead-Tin Yellow, Cremnitz White
- Titanium Pigments – Titanium White, Titanium Beige, Titanium Yellow, Titanium Black
- Zinc Pigments – Zinc White, Zinc Ferrite
- Biological Pigments – Alizarin, Alizarin Crimson, Gamboge, Cochineal Red, Rose Madder, Indigo, Indian Yellow, and Tyrian Purple.
- Non-Biological Organic Pigments – Quinacridone, Magenta, Diarylide Yellow, Phthalo Blue, Phthalo Green, and Red 170
- Carbon Pigments – Carbon Black, Ivory Black
- Clay Earths
- Ultramarine Pigments – Ultramarine and Ultramarine Green
How do Pigments work?
Light waves are selectively absorbed by pigments. A pigment particle can absorb white light by a variety of methods when it does so. Some organic pigments have double-bond linked structures that absorb light. Light may be absorbed by inorganic pigments through electron transfer. For instance, when light is absorbed by vermilion, an electron is transferred from the sulfur anion (S2-) to a metal cation (Hg2+). The majority of the Colours in white light are removed by charge-transfer complexes, which scatter or reflect the remaining light to make it appear as a certain Colour. Unlike luminous materials, pigments absorb or remove wavelengths rather than adding to them.
The impact of Colour combinations on a spectator relies not just on the impacts of the individual Colours but also on how harmoniously they are blended and how the pattern is put together. For ages, artists and designers have studied the impact of Colour and have come up with a wide range of theories on how to use Colour. These ideas are many and diverse, proving that there are no set laws that apply to everyone and that each person’s experience determines how they see Colour.