Beneath what felt like stage lights, which cast yellow pools of light onto the model stand and threw the shadowy recesses beyond into the cool, slate blue darkness of the background (filled with large metal easels, painters' taborets, and abandoned still-life props), I sat perched near the golden glow surrounding a still-life. A palette on the rolling taboret, a tabletop encrusted with years of jewel-toned daubs of paint left by students before me, held gleaming daubs of fiery reds, daffodil yellows, and blues so deep they looked black. With paintbrush in hand, I applied a calculated ribbon of paint to the smooth gessoed surface of a masonite panel. The year was 2001, and I had no clue how lucky I was. The professor in my first college art class was an expert in realistic painting, which was a rarity in university art departments in those days.

Back in the early 2000s, the vestiges of the late-mid-century non-representational art scene were still quite strongly felt within university art departments. In general, there didn't seem to be much interest in trying to catch the way the sun rakes across distant blue hills in a landscape painting or catching the glint of a vase in a still life. In fact, later as a student at RISD, there was a sometimes-stated assumption that realistic technique could be relegated to what is found in craft store how-to books, which it turned out was a bit of an oversimplification. In what could only be termed luck, outrageous divine favor, undeserved blessing, or all of the above, my first painting professor introduced us to the Munsell Book of color and to a powerful split-primary palette that still forms the core of my color mixing. That palette could do a lot, but it did have a couple of slight drawbacks. I took a daub of phthalo blue and added it to my mix, and the phthalo instantly overshot the target color, and turned the whole color cast a bit chemical looking. I counterbalanced that with proportions of cadmium yellow and cadmium red light- a sort of mock Cadmium Orange. Now too dark, the mix needed a bit of titanium white, which cooled it off a bit too much, and so needed a bit more yellow...and on it went until a satisfactory mixture could be found.

Genuine cerulean is a gorgeous, durable, lightfast sky blue that mixes well in realistic painting. PB35 is one of the areas where it may help to know the chemical name, Cobaltous Stannate, in order to differentiate it from an occasional doppelganger, PB36. Genuine cerulean PB35 is sometimes called light cerulean blue, whereas PB36 is sometimes found in much deeper and greener shades. Genuine cerulean is a lovable blue when making lower-chroma mixes.

Lightfastness: Excellent with a few minor caveats.

Transparency: Semi-Opaque,

Relative Dry Time: Medium,

Strength in Tints: Mild (tinting strength tests help to gauge pigment load),

Oil content: Can be high depending on formulation,

Toxicity: Hazardous, handle with proper cautions.

General notes on categories: The transparency of a given paint may vary due to paint formulation. Cerulean is one of the colors where tinting tests are very helpful for judging relative pigment load. Its strength in tints will vary across brands due to how much filler a brand may use. Since cerulean is naturally a rather gentle tinter, it helps to use a high quality sample as a baseline for comparisons.

In comparison to other blues, Cerulean Blue is: -Less strongly tinting and easier mixing pigment than Phthalo Blue, PB15,

-A greener blue than Ultramarine, PB29,

-More of a light sky blue than most Cobalt Blues, PB28

PB35 is commonly called Cerulean Blue, and has a range of names including Caeruleum, Bleu céleste, and the wild spelling, Coeruleum. Sometimes it's described as a middle chroma blue that leans toward the greens, and it creates lovely mixtures with other pigments. Cerulean Blue is usually described as opaque or semi-opaque, depending how the paint was formulated. Oil paints are found ranging from semi-transparent to opaque depending on factors such as extenders and pigment load. This is one of the pigments where tinting tests are very useful, as quality may be shown rather quickly.

The drying time can vary, but it is usually listed as medium (some say fast or average, but some sources may even say slow). In addition to the usual variances caused by driers, the differences in dry time also derive from the binding oil, as Cerulean may be bound more often in alternative oils to reduce yellowing, and those oils often come with longer dry times. According to Mayer, the pigment itself is a good drier. Many paints list 2-7 days as a drying time.

Mayer doesn't seem too concerned about the paint film, and says cerulean tends to form a somewhat flexible oil paint film in linseed oil, however we've heard elsewhere that it is slightly soft, and in his book on paints, Reed Kay gives it a B for film formation. Its lightfastness and toxicity are further discussed below.

A Blue for Skies Cerulean blue was sometimes called bleu céleste, for good reason. Stunning on its own, it's also a gorgeous mixer that plays well with other colors. The remarks of a very accomplished painter of skies caught my attention when he said that for his brilliant, chromatic sunset skies he did not use phthalo in his palette-- he used cobalt and cerulean. Cerulean behaves differently than phthalo in mixes with other colors. Our experience is that there's something more visually comfortable about mixing with cerulean.

** A Highly-Praised Pigment** Older texts praise it for its remarkable stability. In his work on pigments, Doerner said, "...A greenish, light, very pure and dense compound of cobaltous and tin oxides which, as a color, is very valuable to the landscape artist, for example, in atmospheric tones. This color is absolutely durable."

Cerulean was discovered in the early 1800s (it's related to Cobalt Blue or Thenard's blue), but it took a half century for its use to become popular with artists. It was expensive, but it so marvelously replaced azurite that artists sought out this incredible color. It's similar in some ways to cobalt, but it's more of a daytime summer sky color.

Do You Really Need Genuine Cerulean? In the modern era, the big question arises, do you really need cerulean in a world that contains phthalo? For some the answer will be no, but we happen to prefer the way cerulean mixes with other colors. We've heard similar sentiments from a couple of other artists. Those who have been painting a while are familiar with phthalo's intensity, which takes some reigning in. Cerulean blue is the opposite, and its visual presence at full strength and sociable aspect are part of why it's still prized. In other words, the low tinting strength of cerulean is part of what makes it blend well with others, and due to its durability that makes it valuable on the palette. When choosing a blue that will meld well with other pigments in different areas of the spectrum- especially for naturalistic work, or painting wet-on-wet, Cerulean is excellent.

There are a million roads to Rome when it comes to mixing skintones. However, there have been a few times when Cerulean was the right color for a mix.

I love to work from life, and when a model is waiting, there is an unspoken pressure on the mixing, even if the model is the most patient person in the world. The model for this painting was a very patient person, and as I mixed the colors at one of the portrait sessions, I noticed that none of my mixes captured a certain note that I wanted in the undertone. In a moment of inspiration, I thought, it's crazy, but I want to add Cerulean blue.

It just so happens that I had Old Holland Cerulean Blue on the palette. It was the perfect note. I'm sure the same spot color could have been mixed and balanced with toothpick-sized dots of phthalocyanine or viridian or some other combination of forces, but when four or more colors come together in a mix, it is easy to overshoot a mix in a live painting session. Sometimes a person can find themselves spending more time adjusting and mixing than they do painting. Phthalos have a phthalo look to them sometimes, so I wouldn't usually add them to portrait tones.

Since then, there have been a handful of sitters for whom, after a few initial mixes, I find myself reaching for genuine Cerulean Blue.

Cerulean is a candidate for being bound in oils that yellow less, namely safflower and poppy. Writing from the mid-20th century, Wehlte mentioned that it is "only used in poppy oil."

Cerulean blue is often bound in poppyseed oil to preserve its cool blue tones, but poppyseed oil has some potential drawbacks, such as possible issues with drying time as well as cracking. Best practices dictate that if one was to use an alternative binding oil, it's best reserved for the topmost layer of a painting where the color will be best appreciated.

A Note on Walnut Oil We used to think M Graham made a true Cerulean in walnut oil, but it turns out the pigment is actually PB36. We have also experienced a bit of chalking a while after the paint dried. This happened when the paint was applied thinly at full strength with a palette knife on panel.

For general mixing, we tend to opt for PB35 in linseed, however, for areas where the blue masstone is most important, we might entertain the idea of other binding oils used sparingly in the top layer of the painting.

Cerulean is a moderate tinter-- not the faintest, and certainly not the strongest. So, when performing tinting tests, it's helpful to have some high-quality samples by which to judge a prospective brand.

Getting to Know Cerulean Since Cerulean is a naturally gentle tinter, be sure to try a high quality cerulean so you have something with which to compare your samples as a reliable baseline for quality. Once you get to know a high-end cerulean, you'll also understand it's peculiar behaviors.

Cerulean isn't always the loveliest texture in oils-- sometimes cerulean seizes a bit when being worked with a palette knife, and it's naturally a little gritty. This beautiful, stable blue is not the butteriest, and that's how it should be.

In Search of Genuine Cerulean Samples

We only know of one company right now that sells a sample set that includes a high quality genuine cerulean (if you know of another, let us know). Since it's an expensive pigment, it is almost never seen in sets.

However, we just learned this week that the 11ml sample sets by Williamsburg will no longer be offered. We were devastated to hear that these mini-sets were no longer being made available, as painters need accessible entry points to try the more expensive colors without having to invest a large sum.

So if you are reading this while they are still available, this set, which contains several cadmiums as well, is currently around $47 when ordering from the States. It's called the Williamsburg 11ml Traditional Sampler Set. So while11ml is super small, it contains several mini-tubes of cadmiums, a full-sized 37ml Titanium white, and is a great way to try some of the more expensive colors.

Cerulean Blue, PB35, has excellent lightfastness, with slight caveats.

Historically, PB35 has a reputation for excellent lightfastness with highest marks (solid 8s on the BWS). In Golden’s Lightfastness Testing in oils, in tints Cerulean performed at ASTM I (excellent) in several whites which were tested.

Slightly More Change in Lead White and Zinc Oxide In Golden's tests, Cerulean performed at an ASTM II (Very Good) in Lead White in Linseed as well as pure Zinc Oxide. While Cerulean did well in outdoor sunlight it showed a dramatic and surprising sensitivity to artificial simulations such as QUV and Xenon.

In the past it has been rated at ASTM I in watercolor, though Bruce MacEvoy mentions some quirks that occurred in watercolor. Refer to his research for more.

Each pigment, when made into oils, has different oil requirements. This is an interesting note when companies mention a high pigment load-- each pigment has a different relationship to the oil, and dictates how much oil is required. Some pigments need more oil than others to be made into a paint. Another element, which becomes relevant with cerulean blue in particular, is that those fillers and extenders that paintmakers might be tempted to add also have their own oil requirements. Some extenders and fillers require a lot of extra oil, and some also yellow more severely.

Oil requirement patterns for pigments may be helpful to know if painting in layers, for example one can choose a less oily pigment for underpainting. In oils, different Cerulean Blue pigments may have slightly different oil absorption amounts, and PB35's oil content by volume when made into a paint may be quite high compared with other pigments. Wehtle merely says, "As high as cobalt blue," which is one of the pigments with high oil requirements. Mayer, in his 1970 work, categorizes Cerulean Blue as requiring a high oil volume with a score of 112. However, Williamsburg lists their version on this chart. They list their Cerulean as having a moderately low amount of oil when linseed is the binder. We would love to see every brand list oil content by volume for their paints, as there can be a lot of variation at times.

Poppyseed Oil Cerulean Blue may also be bound in alternative oils such as poppy or safflower in order to help preserve the look of the blue and avoid yellowing. It may be helpful to note that poppy and safflower are often reserved for the uppermost layer of a painting for their own reasons.

Further Notes For Cerulean Blue, some sources suggest high to very high oil requirements by volume depending on the binding oil, so clearly opinions vary.

A side note on weight vs volume: it gets confusing, but oil content by volume is totally different than oil requirements by weight. The figure by weight may be more helpful for paintmakers, while painters may find volume ratios more helpful in planning out their painting layers. For oil absorption by weight, refer to the main entry for PB35 in the Pigment Notebook for more details.