Several paint companies are now calling things burnt sienna, raw sienna, raw umber and burnt umber that are not those pigments at all, but mixtures of synthetic pigments. These substitutes do not share the same characteristics as the real pigments they’re named after. Some are more transparent, some more opaque, some are even the wrong hue, and the drying characteristics are different.
I’m opposed to this practice because it generates confusion. So when you read or hear me speak of burnt sienna, raw sienna, raw umber or burnt umber, please understand that I’m speaking of the real stuff, not the synthetic substitutes.
Umbers and ochres contain clay, which is hygroscopic and undergoes shrinking and swelling due to changes in relative humidity. Synthetic iron oxide (Mars) pigments are more stable in that regard, are lightfast and high in tinting strength. That being said, natural earth pigments have a long record of good performance, and are as lightfast as the Mars colors, which is to say, more lightfast than anything else.
The natural earth pigments have a long history in oil painting, and can be expected to perform as well into the future as they have up until now. They were staples on my palette for almost 60 years. But Marion Mecklenburg’s report on the shrink/swell tendencies of yellow ochre and burnt umber has influenced me to use Mars yellow instead of yellow ochre. I had already stopped using umbers due to the sinking-in issue. I still use real burnt sienna and green earth. I might be considered a fanatic on long-term durability for phasing out yellow ochre over that one fault, but I find Mars yellow works well in its place, without the shrink/swell tendency.
An additional note: Marion Mecklenburg did a very long series of tests on oil paints, and concluded that umbers and yellow ochre are particularly problematic because they’re hygroscopic. They’re clays, which are highly absorbent, so they undergo fairly drastic changes in response to moisture in the air. They shrink and swell with changes in humidity, which creates stresses in the paint films and can cause cracking.
The Color of Art Pigment Database lists historic brown pigments, natural browns, and pigment browns.
The pigment ‘color’ can be PBr6 or PBr7 depending on the maker, which adds confusion. You might see shades of yellow-orange, red and violet-brown or green-brown, depending on the ratios of hydrated iron (yellower) to anhydrous iron (Redder), and the presence of other clays & minerals.
Transparency depends on many factors, including particle size, binder, fillers, and extenders, and the composition of the base clay in the natural product.
Pigment Number: PBr7, PY43
Technical note: PY43 is now the notation for Raw Sienna instead of PBr7.
According to George O’Hanlon of Natural Pigments: PY43 is the correct notation for Siennas, since it consists primarily of an iron oxide earth pigment. Just like Golden, we are revising the Colour Index names for Siennas offered by Natural Pigments to reflect this nomenclature. We originally believed, as did much of the pigment industry, it was correct to label Siennas as PBr7, but we are agreement with Golden in this assessment. This has nothing to do with substitutions or the sophistication of pigments, but rather simply the classification of earth pigments that are often bewildering in variety and source.
Pigment Number: PBr7, PY43
In 2021, ASTM International decided that burnt sienna should be called PY 43 instead of PBr 7. No different pigment, just a different number. Possibly not all paint companies have bothered to change their labels yet.
When I mention burnt sienna, I’m talking about the real, natural earth pigment called burnt sienna, not any substitute pigment that a manufacturer has labeled “Burnt Sienna” which is actually a synthetic iron oxide or a mixture of three pigments, as some companies are doing now. There are differences in drying times, tinting strength, and opacity/transparency, and in the case of Winsor & Newton, even the hue is different. These are NOT burnt sienna, and it is confusing and misleading for paint companies to use that name for them.
Brands that offer genuine Burnt Sienna (PBR7): Rublev, Gamblin, Blockx, M. Graham, Old Holland, Williamsburg, Michael Harding, Maimeri Puro, Holbein, Daniel Smith.
Brands whose Burnt Sienna is in name only: Winsor & Newton’s is PR 101, and so is Rembrandt’s. Sennelier’s is PBk 11 (Mars black) +PR101 (synthetic iron oxide)
There may be some variation from one burnt sienna to the next, but they’re all in the same general range of hue, opacity, and drying times if they’re real burnt sienna instead of synthetic substitutes.
Note: some paint companies substitute modern synthetic pigments or combinations of them for traditional pigments, and yet still call them by the same names. I object to this because it creates confusion.
— Properties of real burnt sienna? —
Burnt sienna is another pigment that causes sinking in, though not as badly as burnt umber, but usually the final varnish evens out the gloss of burnt sienna and other non-umber earth pigment passages satisfactorily.
— Comments on the synthetic substitutes —
I should add that the synthetic iron oxide pigments are very good pigments, whose lightfastness is comparable to the natural earths, and will probably outlast them over the centuries, but their drying times and tinting strength are not the same as the real earth pigments, so some adjustment to them is necessary.
Pigment Number: PBr7
The sinking-in effect ((spots that dry matter and appear lighter in value and duller in color than they were when the paint was wet) is less of a problem for raw umber than burnt umber.
A Facebook reader asked if raw umber also darkens the way that burnt umber might (the suggested reason was that the manganese in raw umber can darken over time).
Virgil responds: “I haven’t seen any instances of raw umber darkening, so I would tend to doubt that it does. Keep in mind, however, that as dirt dug out of the ground, there are variations from one mine to another, and probably even from one depth to another in the same mine. It’s not a consistent material, so there might well be some batches that behaved in that way at one time or another. I just haven’t seen it. Winsor & Newton began adjusting raw umber from a new source by adding phthalocyanine green to it after customers complained that it was not the same color as the old raw umber from a mine that had played out. So if a raw umber from W&N that was adjusted in this way is one that darkened, it might be due to the added pigment rather than the umber. The bottom line answer is just that I don’t know. One can paint every bit as well without it as with it, so if one is concerned, the cautious course would be to simply not use it.”
The Pigment Through the Ages website offers a description of Umbers. Umber is a natural mixture of iron and manganese oxides and hydroxides. Its earth tones vary depending on the amount of the iron and manganese compounds. Raw umber is just the earth mined and ground into a pigment. But it can be calcinated in order to obtain darker shades (Burnt Umber)
Pigment Number: PBr7
Pigment Number: PBr43
Mars Brown is an inorganic, synthetic brown made of iron and manganese oxide. It’s oqaque, with high tinting strength, and is fast drying.
Natural Pigments describes their Mars Brown as: “a deep reddish brown with a subtle purple cast in masstone. More than Mars brown this color has similar chemical make-up as natural yellow ochers and brown umbers. Since this deep brown is modified with a certain amount of manganese oxide, it displays excellent stability and lightfastness.”
An article Virgil Elliott wrote for Natural Pigments in August 2020 includes these notes:
Mars brown is one of the paints listed in William Bouguereau’s notebooks, and it appears in mixtures with white in the flesh tones in his paintings of light-complected people, for which he is widely renowned among artists. Its high tinting strength makes it one of the ideal paints for tinting lead white for underpainting because so little of it needs to be added to lead white to create a range of values, thus allowing the underpainting’s primary ingredient to be lead white, which is the most perfectly suited paint for the underpainting of all oil paints in existence for its fast drying, its high pigment volume concentration, its superior film strength, and for the beneficial effects it imparts to all the paints in the ensemble. The white I use for underpainting is Rublev Lead White #1, which begins to set up in 6–8 hours and perfectly suits my painting ways.
I have eliminated umbers from my palette for reasons explained in my book, which I won’t bother to go into here because this is about Rublev Colours’ Mars Brown, Transparent Red Iron Oxide, Transparent Yellow Iron Oxide, and Chromium Oxide Green. With Mars brown on my palette, the absence of umbers is no great handicap. Mixed with bone black, it can substitute for burnt umber quite satisfactorily. Mixed with green, it can take the place of raw umber. Its high tinting strength means that if used primarily in mixtures, rather than alone, one tube of Rublev Colours Mars Brown will last a very long time. Mars brown, an iron oxide pigment, is as lightfast as any natural earth pigments, including burnt sienna. These are the most lightfast pigments in existence. It’s important to me that none of the colors in my painting will fade or change in any significant way for centuries (or ever, if that can be achieved. With Mars colors, that might well be possible.) Mars brown is more opaque than umbers and siennas.