Cadmium Yellow

What color is cadmium yellow?

The story of cadmium yellow

Before cadmium yellow, every bright yellow on the palette came with a catch.

The metal came first. Friedrich Stromeyer found cadmium in 1817 in impure zinc from a Göttingen pharmacy; the story is on the cadmium red page. Cadmium sulfide made an obvious yellow, but the metal was so scarce that nobody could sell the pigment at a painter's price until the 1840s. Chrome yellow, the bright lead chromate of the day, browned with age, and painters moved to cadmium as soon as they understood that. Van Gogh used it. So did Monet, and the Art Institute of Chicago has since found cadmium yellow in two of his Stacks of Wheat of 1890 and in a Water Lilies of 1906.

One compound, several tubes. Pure cadmium sulfide, PY37, gives the medium and deep yellows; add zinc sulfide and it shifts toward green, which is cadmium lemon, PY35; swap sulfur for selenium and it slides through cadmium orange, PO20, into cadmium red. All of them are opaque; a stroke of cadmium yellow medium sits on the paper like a painted door. It does fade on fresco walls, where it slowly turns to carbonate, and in 2023 researchers found that a cadmium lemon Joan Miró favored had faded because of how its atoms were arranged, but those are the exceptions. In a sketchbook, a cadmium yellow from 1890 looks like one from last week.

Cadmium orange gets its own paragraph because nothing else does its job. It is the red's chemistry with less selenium, and it is the most opaque member of the family, a color that covers a mistake in one coat and still looks clean. Every orange mixed from a yellow and a red is more transparent and a shade duller. If you paint marigolds or the underside of a sunset cloud, one pan of it saves an afternoon.

Aureolin is the cautionary tale in the same drawer. Nikolaus Wolfgang Fischer, a chemist in Breslau, made potassium cobaltinitrite in 1831; Edouard Saint-Evre made it again in 1851 and 1852 and put it in front of painters, who called it cobalt yellow. It was the first good transparent yellow, expensive, and it glazes like stained glass. Then the reports began to disagree: permanent in some tests, unstable in oil in others, and in watercolor liable to fade to a grayish or brownish yellow. I do not own a pan, and I would not put it on anything I wanted to keep.

Now the label, in brief, because the red page covers it in depth. Cadmium is toxic and its compounds are classed as carcinogenic, but the pigment is nearly insoluble, so the danger is dust rather than wet paint; Sweden asked Europe to ban it from artists' paints in 2013 and was refused, so the tubes are legal and not for children. The cadmium-free shelf answers with organic yellows: arylide or Hansa yellows like PY74, a German discovery of 1909, and the benzimidazolone yellows PY151 and PY154, patented in 1960 and very tough. They match the hue. They do not match the behavior: they are semi-transparent, they stain, and in a wash they glow where cadmium sits. Not worse. Just different, and worth knowing.

Pigment facts

These describe the pigment in general. Every brand's tube behaves a little differently, so test yours on scrap paper.

How to mix cadmium yellow

You cannot mix a cadmium yellow. It is a primary, and its body, the reason to buy it, is exactly what mixing takes away. What you can do is mix around it: a touch of red pushes any warm yellow toward cadmium orange, a speck of green pulls it toward the lemon.

Blue is the pairing that matters, and cadmium yellow is fussy about which blue. A green-leaning blue like Glacier Blue or phthalo blue gives solid, opaque spring greens; ultramarine gives a softer olive, which is usually the green you want outdoors. The old recipe for cadmium green was cadmium yellow and viridian, and it still works.

Using cadmium yellow in watercolor

Use cadmium yellow where the sun is actually landing: the lit half of a lemon, a field of rapeseed, a child's raincoat. It comes forward and it covers, so it is the yellow for the last, brightest touches on a dry painting, never the first wash.

Dry brush is where the opacity pays. Drag a fairly dry brush of it across rough paper over a dried blue or green and you get broken light on water or leaves that no transparent yellow gives you.

Its friends are the dull colors. Next to yellow ochre it sings and the ochre looks calmer; next to Payne's gray or a violet it glows. Next to another bright yellow it just shouts.

Here is the thing I learned the hard way: keep it out of your glazes. I once floated a thin cadmium yellow over a finished sky to warm it and got a chalky veil. Glaze with a transparent yellow and save the cadmium for the top layer.

Cadmium yellow vs cadmium orange (and aureolin)

Selenium is the difference between cadmium yellow and cadmium orange: the orange is the same chemistry pushed toward red, and the most opaque of the three. Side by side with cadmium yellow deep, the orange covers better and mixes duller. Buy the orange if you paint fruit and sunsets, the yellow if you paint everything else.

Then there is aureolin, the opposite kind of yellow: cobalt instead of cadmium, transparent instead of opaque, a glaze instead of a body color, and lightfast only in some of the tests. Where cadmium yellow sits on the paper, aureolin sinks in and lets the white glow through; where cadmium yellow lasts, aureolin may not.

If cadmium yellow is a coat of paint on a door, cadmium orange is the same door at sunset, and aureolin is light through a stained-glass window: lovely, and not guaranteed to be there next year.

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Mel, founder of Tobio'sI make portable watercolor kits and I named the company after my cat. I write these pages for the beginner I used to be, one pigment at a time.