The Palette/red/Made in a lab or a works
Cadmium red
The first bright red that is neither poisonous mercury nor a fading plant, and it is cadmium, so it is poisonous too.
- Hex
- #E30022
- RGB
- 227, 0, 34
- Pigment index
- PR108
- First used
- 1910 commercially
- From
- Germany
What it is
Cadmium sulfoselenide, CdS·CdSe. The ratio of sulfur to selenium sets the hue from orange through scarlet to deep maroon.
How it is made
Cadmium salts are precipitated with sulfide and selenide, then calcined (fired) to grow the crystal to the right size. The firing is what makes it lightfast and it is also what sets the shade, along with the selenium content. More selenium, deeper red.
Cadmium yellow came first, in the 1840s. The reds waited for the selenium chemistry and arrived commercially around 1910, immediately displacing vermilion for anyone who cared about either their health or their budget.
Cadmium red, Class of pigments that have cadmium as one of the chemical components. Wikipedia's description, not ours.
The history
For the whole history of painting before this, a bright red was a compromise: vermilion was brilliant and toxic and could blacken, madder and cochineal were beautiful and faded, red lead was cheap and unstable. Cadmium red is brilliant, opaque, completely lightfast and utterly stable. Matisse's late work depends on it. So does most twentieth-century abstraction that has a red in it.
Its problem is environmental rather than pictorial. Cadmium is a cumulative toxin and a serious water pollutant, and there have been repeated attempts in the EU to restrict artists' cadmium paints, most recently a proposal that was argued down after objections from painters and conservators. The industrial uses were restricted long ago; the artists' exemption survives because the quantities are tiny and there is no true substitute.
That 'no true substitute' claim is worth examining, because it is made about every restricted material and is usually wrong. In this case it holds up better than most: the pyrrole reds (PR254 and relatives) get very close and are genuinely excellent, but they are transparent where cadmium is opaque, and opacity is not a preference. It changes what the paint can do.
Where it is used
Artists' paint, and historically plastics, glass, ceramic glaze and industrial coatings. Cadmium-glazed pottery and enamel are why some mid-century kitchenware is that particular orange-red.
As a colour it is the most purely advancing red available: opaque, warm, and it will not sit back in a composition whatever you do to it. That is exactly why it is on so many warning signs and sale stickers. If you need a red that does not shout, do not start here, start at alizarin or a cool earth red and you will save yourself a fight.
Go and look at it
Matisse's late cut-outs and paintings
Tate Modern, London; MoMA, New York; Musée Matisse, Nice
Flat, opaque, unmodulated red at full strength. Only a cadmium will hold that without going pink or dull.
How it behaves
- Made of
- Cadmium sulfoselenide, CdS·CdSe. The ratio of sulfur to selenium sets the hue from orange through scarlet to deep maroon.
- Opacity
- Opaque. It covers what is under it.
- Lightfastness
- Permanent. It will outlive the thing it is painted on.
Hazard
Cadmium compounds are toxic and a cumulative environmental pollutant. Do not sand, spray or breathe.
- Completely lightfast and stable in every medium, which is why it survived the health objections.
- Very opaque. This is the property the substitutes cannot match.
- Hue is set by the selenium content, light, medium, deep and maroon are one chemistry at four ratios.
The numbers
All derived from the hex, never typed beside it
- HEX
- #E30022
- What a browser and a design file want.
- RGB
- 227, 0, 34
- The same three numbers in base ten. Light, not ink.
- HSL
- 351°, 100%, 45%
- Hue, saturation, lightness, how a person describes a colour.
- CMYK
- 0, 100, 85, 11
- Arithmetic only. A real separation depends on the press, the paper and a profile.
- LAB
- 48, 74, 49
- Perceptual. L* of 48 is how light this actually looks, which HSL gets wrong.
This hex is an approximation, and a page about pigment has to say so. Cadmium red is a substance. A ground mineral scatters light from thousands of separate grains at slightly different angles, and no single sRGB value is that event. It is a flat average of a photograph of it, and the real thing is outside what a screen can emit. Use the number to specify a screen colour. Do not use it to judge the pigment.
Where it sits on the wheel
Hue 351°
Its opposite, by the diagram
The arithmetic opposite, 180° round in HSL. Useful, and not the same as the opposite a painter mixing pigment would name, that wheel was built for paint.
Lighter and darker
Towards white
Mixing with white does not only lighten, it dulls and cools. This is why a pale tint of a brand colour so often looks chalky, and why a designed light shade beats a generated one.
Towards black
Mixing with black kills the hue as it darkens. A better dark is usually the colour plus its neighbour round the wheel, which is what every painter does instead.
Can you set type on it
Handgloves
White on it
4.90:1 · AA
Handgloves
Black on it
4.29:1 · Large text only
Handgloves
It on paper
4.65:1 · AA
Handgloves
It on ink
3.74:1 · Large text only
4.5:1 is the floor for body text and 3:1 for large text, by WCAG. Treat it as a minimum you may not go under rather than as a target: plenty of pairs pass at 4.6:1 and are still unpleasant to read for a page, and the checker will not tell you that.
Read more, elsewhere
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