Color Spotlight: Azo Yellow (PY151)

Azo yellow, short for benzimidazolone yellow, is a super bright lemon to middle yellow that mixes clean, bold oranges and greens.

Pigment Stats for PY151

Chemical Composition: Monoazo benzimidazolone

Lightfastness: Excellent (confirmed by my tests – see below)

Toxicity: Nontoxic

My Observations of Daniel Smith – Azo Yellow

Color Family: Lemon Yellow

Handwritten notes: “Transparent. Dries lighter/less vibrant.”

Hue: A bold, middle yellow.

Gradient: Smooth gradient, with a somewhat abrupt transition from midtone to dilute.

Transparency: Transparent.

Drying Shift: I did notice a bit of a drying shift on this one which mostly affect midtones which appeared evenly yellow but had a tendency to dry a bit patchy. I think this could be overcome with practice to ensure it has the right dilution when wet even though it’s hard to tell visually until it dries.

Color Mixes: Leans cool in mixes (e.g. it makes lemony neons with Cobalt Turquoise Phthalo Green), but still makes bold oranges. A versatile mixing yellow.

Lightfastness

These look identical to me. Totally lightfast as far as I can tell!

Comparison to Other Brands

Schmincke Horadam – Aureolin Hue

A lovely super bold candy yellow! I found this one brighter unmixed than DS. It was easier to get the right dilution, both for a smooth gradient and an even flat wash. I didn’t even have my usual Schmincke hard-edge problems! The mixes are similar to DS; perhaps slightly cooler.

PY151 is the yellow mixer in Schmincke’s May Green; you can see my self-mix of that color in the mix with Phthalo Green (PG7). I like how it makes a spring green that’s very bright and cool but not neon-ish.

Comparison to Other Yellows

Azo Yellow shares Nickel Azo Yellow’s property of being warmer in masstone and cooler in dilute, although Nickel Azo Yellow is much more pronounced and actually gets brownish in masstone, which Azo never does.

Unmixed Azo Yellow looks somewhere between Imidazolone Lemon (PY175) and Imidazolone Yellow (PY154), perhaps leaning slightly more toward the middle yellow. However, as I mentioned above, I think it mixes more like the lemon.

Color Mixes

Isoindolinone Yellow Deep (PY110)

The cooler yellow of the PY151 mixed with the warm PY110 make a range of New Gamboge to sunflower yellow hues. In dilute, they have a translucent caramel appearance.

Quinacridone Burnt Orange (PO48)

Compared to Nickel Azo Yellow, it makes a less dispersive, more primary-yellow-looking quin gold hue with QBO. 

Perylene Red (PR178)

The slight mutedness of PR178 results in slightly brickish or terra cotta type oranges, with gold on the more yellow end. In dilute, you wind up with a peachy shade in the middle, possibly useful for portraitists for a white person skin tone.

Quinacridone Coral (PR209)

These colors are deep and intense but don’t quite hit a bright orange the way you would with the mix of PR209 + warm yellow (e.g. PY65/PY110).

Quin Rose/Red (PV19)

Similar to PR209 mixes, but one step more muted. I found it difficult to get to a red or even a clear orange with these, but they do make “ruby red grapefruit.”

Phthalo Blue Green Shade (PB15:3)

Vivid foliage greens and turquoises.

Phthalo Green Blue Shade (PG7)

Clearer, more vivid spring greens than one can achieve with the Phthalo Blue.

Phthalo Green Yellow Shade (PG36)

Very similar to PG7 greens; erring a bit yellower.

What Others Say

Benzimidazolone yellow PY151 is a very lightfast, semitransparent, staining, very light valued, intense yellow pigment… Even though its saturation is high, the light yellow hue position means it can easily take on a slightly brownish cast. In watercolors PY151 undergoes a very small drying shift, barely shifting in lightness or saturation.

Bruce MacEvoy, handprint.com

PY151 is benzimidazolone yellow, aka Azo Yellow (Daniel Smith) or Aureolin Hue (Schmincke). It’s an intense slightly cool yellow. This is probably one of the more vibrant yellows around, other than PY175 Lemon Yellow. This paint cost more as it’s from a more expensive series. Works great as a primary yellow too.

Teoh Yi Chie (Parka Blogs), Yellows made with PY150, PY151, PY153, PY154 and PY159

On Daniel Smith Azo Yellow:

A beautiful transparent yellow; sometimes I have Hansa yellow medium, but I prefer Azo as it’s more transparent.

Lisa Spangler, What’s On My Palette?

My Review of Azo Yellow

I was inspired to try this yellow because of Lisa Spangler’s palette profile, and I’m glad I did! It’s a lovely bold color unmixed, and a very smooth mixer because of its transparency.

My initial thought was that it might be a more versatile yellow than most because of the way it tends to look warmer in masstone and cooler in dilute, like Nickel Azo Yellow (PY150), but I found in practice that it mixes a bit more like a cool/lemon yellow than a typical middle yellow. This is the color for you if you tend to prefer cool yellows like Hansa Yellow Light (PY3) or Imidazolone Lemon (PY175) and want something strong and transparent with a less obviously green-toned appearance unmixed. I think this would be great for the Spring Palette.

Favorite version: Shockingly, Schmincke! While I find that overdiluting is usually far too easy in Schmincke colors, in this color it was DS that tended to overdilute and Schmincke that handled more easily. That said, they mix very similarly, so if using it primarily for mixes it may not matter.

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Schminck Horadam – Aureolin Hue, 5ml tube: Jackson’s US

Note Aureolin Modern is the same thing as Aureolin Hue. Schmincke seems to use both names.

Daniel Smith – Azo Yellow, 15 ml Tube: Blick | Utrecht