Beta naphthol scarlet PO5 is an impermanent, semiopaque, staining, mid valued, very intense red orange pigment. Unrated by the ASTM (1999), my 2004 tests showed the tints faded significantly after six weeks of sunlight exposure, earning it a "fair" (III) rating. In watercolors PO5 undergoes a small drying shift, holding its lightness and losing saturation slightly. The average CIECAM J,a,b values for this beta naphthol scarlet (PO5) are: 51, 72, 50, with chroma of 87 (estimated hue purity of 70) and a hue angle of 35.

The Lukas permanent red light, now discontinued, was the only commercial paint I know to use this pigment. The color appearance and handling attributes were similar to pyrrole orange (PO73), but distorted by the apparent presence of brighteners and extenders.

AVOID. Given its poor lightfastness and the more lightfast pigments with identical color appearance, this is an irrelevant pigment for professional artwork. Substitutions: Cadmium orange (PO20), pyrrole orange (PO73) and perinone orange (PO43) are more intense (an average chroma of 88 compared to the benzimidazolone's 85) and far more lightfast pigments, and have better tinting strength than the Lukas paint. See also the section on naphthol pigments.

lightfastness test sample

unexposed (top); exposed 800+ hours (bottom)

TOP 40 PIGMENT  Cadmium orange PO20 is a very lightfast, semiopaque, heavily staining, moderately light valued, very intense yellow orange, orange and red orange pigment. Genuine cadmium sulfide is available from 10 pigment manufacturers worldwide; only 2 manufacturers offer the cadmium coprecipitated with barium sulfate (cadmium lithopone, which does not have a separate color index name). The ASTM (1999) rates its lightfastness in watercolors as "excellent" (I), and most manufacturer and my own tests agree. In my experience the orange and red shades are less susceptible to the impermanence (darkening) caused by manufacturing impurities in some cadmium yellows. (The brighter cadmium vermilion, PO23, made with mercury, is not used in artists' colors because of its toxicity and poor lightfastness.) In watercolors PO20 undergoes a moderate drying shift, darkening slightly and losing saturation by up to 20%. (Loss of saturation or value has a greater impact in orange colors, however, due to the apparent change in hue from orange to brown.) The average CIECAM J,a,b values for cadmium orange (PO20) are: 60, 59, 58, with chroma of 82 (estimated hue purity of 67) and a hue angle of 44.

Cadmium has been an important artists' colorant since the yellow hue was discovered and commercially introduced in the mid 19th century (the orange and red hues were introduced in the early 20th century), but 19th century usage was limited by cadmium's high price and the impermanence introduced by manufacturing impurities. Cadmium sulfoselenide can take any middle to deep shade of orange; to produce a specific orange hue or a lighter value, paint manufacturers sometimes mix cadmium orange or red with cadmium yellow (PY35). (This cadmium color key suggests the variations.) High quality cadmium is extremely durable, covers very well, is easy to handle, is moderately active wet in wet, and blossoms readily if wetted while still moist (although it is resistant to blossoming once dried). It has a powdery luster on the paper, and dilutes down to muted, clean, near transparent tints. All these characteristics give it an unusual and delightful range of texture effects; the only drawback I can think of is its tendency to stain paper aggressively.

Most of the brands tested here were equivalently semiopaque, staining, and moderately dark valued, with chroma in the range 89 to 92, but the MaimeriBlu and DaVinci paints were especially dark valued, warm oranges, while the Blockx and Schmincke red orange paints were the dullest and darkest paints in the list. (Shifts in hue have a very noticeable impact on the lightness and chroma of orange paints as the hue shifts from yellow to scarlet, so take hue into account when you compare brands.) Both the Rowney Artists and Rembrandt cadmium oranges are mixed with cadmium yellow, and the yellower Blockx and Schmincke oranges are probably shade mixtures as well. (The Winsor & Newton and Holbein oranges are mixed from cadmium red and cadmium yellow; see under PR108 at the bottom of this page). These mixed cadmiums seem to have a more pronounced duochrome character, with an undertone shifted noticeably toward yellow. Daniel Smith cadmium orange is the most transparent and active wet in wet, with a nicely centered orange hue. The Schmincke cadmiums are lighter valued (the "deep" is lighter than the Daniel Smith orange, the red orange is lighter by far than the Blockx), and though saturated they lack the powdery glow of a high grade cadmium.

PO20 adds bright color near the center of the warm side of the color wheel. Painters who want to create vivid warm orange mixtures often choose it for their palettes, as oranges mixed from a red and a middle yellow paint are usually dull in comparison. (This depends on the mixing paints used, however: see the color mixing comparisons in the color vision section.) Cadmium is difficult to mix with synthetic organic pigments with low specific gravity (such as iron blue, phthalo green, phthalo blue, dioxazine violet, quinacridone violet, perylene red, etc.) because the cadmium quickly sinks in the mixture; to judge the mixed color accurately, brush out a test swatch and let it dry. I enjoy the lustrous dark colors produced by the mixture of cadmiums and phthalos, but for best results all cadmium paints must be applied confidently, in slightly diluted, juicy strokes without any fussing or reworking, otherwise mud or dull color will result. Cadmium quickly dissolves and charges a wet brush (a plus for plein air painting), but it also clings to the tuft, which means you can quickly muddy your rinse water if you do not wick your brush before rinsing. The main drawbacks to cadmium paints are price: for a similar warm orange color, opacity and mixing range, at lower cost, consider benzimidazolone orange (PO62) or pyrrole orange (PO73). See also the section on cadmium pigments.

Dizazopyrazolone orange PO34 is a fugitive, semiopaque, staining, mid valued, very intense red orange pigment. In watercolors PO34 undergoes a small drying shift, holding its lightness and losing saturation slightly. Unrated by the ASTM (1999), Lukas claims that "None of these premium quality colours got a lower lightfastness than 6 on the woolscale. LUKAS moist water colour gives the maximum technical reliability for the high demanding artist." However, as you can see at right, my 2004 tests revealed substantial fading in tints and some darkening in masstone after 3 weeks of sunlight exposure, and by six weeks both tint and masstone had seriously faded (BWS 3). The average CIECAM J,a,b values for this dizazopyrazolone orange (PO34) were: 54, 71, 44, with chroma of 83 (estimated hue purity of 69) and a hue angle of 32.

Lukas cinnebar red, now discontinued, was the only commercial paint I know to use this pigment. The color appearance and handling attributes are similiar to pyrrole orange (PO73), but in this paint there is visible addition of brighteners and fillers.

AVOID. Given its poor lightfastness and the available pigments with equivalent color appearance, this is a completely irrelevant pigment for professional artwork. Substitutions: Cadmium orange (PO20), pyrrole orange (PO73) and perinone orange (PO43) are more intense (a peak chroma of 95 compared to dizazopyrazolone 's 80) and far more lightfast pigments, and all have higher tinting strength.

lightfastness test sample

unexposed (top); exposed 800+ hours (bottom)

Benzimidazolone scarlet PO36 is a very lightfast, semiopaque, staining, moderately dark valued, very intense red orange pigment. Unrated by the ASTM (1999), manufacturer and my own tests find "excellent" (I) lightfastness. In watercolors PO36 undergoes a small drying shift, holding its lightness and losing saturation slightly. The average CIECAM J,a,b values for benzimidazolone vermilion (PO36) in watercolors are: 48, 76, 49, with chroma of 90 (estimated hue purity of 71) and a hue angle of 33.

The Art Spectrum and DaVinci paints are the only commercial sources I know of for this pigment in watercolors. The color appearance, handling attributes and lightfastness are nearly identical to pyrrole orange (PO73), which is a completely satisfactory substitute with higher chroma (95, compared to benzimidazolone's 85) and better tinting strength; but the lower chroma pigment may produces a more satisfactory range of mixtures with other paints. See also the section on benzimidazolone pigments.

 Perinone orange PO43 is a lightfast, semiopaque, staining, mid valued, very intense red orange pigment, offered by 10 pigment manufacturers worldwide. Unrated by the ASTM, my 2004 tests assign it a "very good" (II) rating, with a very slight and attractive darkening of the masstone color after 6 weeks of sunlight exposure (BWS 6). In watercolors PO43 undergoes a moderate drying shift, darkening slightly and losing saturation by more than 15%. (Loss of saturation has a greater impact in orange colors, however, due to the apparent change in hue from orange to brown.) The average CIECAM J,a,b values for perinone orange (PO43) are: 53, 72, 52, with chroma of 88 (estimated hue purity of 72) and a hue angle of 36.

PO43 varies slightly across manufacturers in lightness and chroma. MaimeriBlu orange lake is the lighter, more intense (chroma of 90) and transparent version of this lovely red orange pigment, and was also the most durable in my lightfastness tests; Utrecht perinone orange is very similar in hue and saturation. Both paints lose saturation slightly under prolonged light exposure. Daniel Smith perinone orange is the darker valued, less intense hue: warmer, more opaque and slightly granular, overall a beautifully rich and lyrical paint.

PO43 keeps its red orange hue from full strength through tints with little hue shift, and makes an excellent red orange paint at color point 3 of the artists' color wheel. If you like this paint, it is worth doing your own lightfastness test to confirm it suits your needs. I prefer cadmium scarlet (PR108) or pyrrole orange (cadmium scarlet (PO73) for a red orange, as both have better chroma and tinting strength in mixtures. Holbein cadmium red orange (PR108) is the closest hue and value match to the average shade of perinone orange. See also the section on perinone pigments.

lightfastness test samples

unexposed (left); exposed 800+ hours (right) — Daniel Smith, Maimeri, Utrecht

 Benzimidazolone orange PO62 is a lightfast, semiopaque, staining, moderately light valued, intense orange pigment, offered by only two pigment manufacturers worldwide. The ASTM (1999) rates its lightfastness in watercolors as "very good" (II), but my own and manufacturer tests find "excellent" (I) results across all brands. In watercolors PO62 undergoes a small drying shift, holding its lightness and losing saturation by 15%. The average CIECAM J,a,b values for benzimidazolone orange (PO62) are: 65, 50, 59, with chroma of 77 (estimated hue purity of 63) and a hue angle of 50.

Because of the limited number of manufacturers, all watercolors made with PO62 have very similar chroma, semiopacity, staining and mixing strength, but the hue is variable, and the undertone shifts toward yellow, sometimes by a substantial amount. The MaimeriBlu permanent orange is the lightest valued with high chroma, Daniel Smith permanent orange is warmer (redder), darker valued, less saturated and more transparent than the other brands. Winsor & Newton winsor orange has an intermediate hue with a nice luster, and is the most staining and the most active in wet applications. Most paints are active in wet applications (blossom, diffusion), probably due to a dispersant added by the pigment manufacturer. The Lukas helio genuine orange had a whitish color suggesting the presence of brighteners or additives.

An interesting middle orange pigment, yellower and lighter than cadmium orange or perinone orange (PO43), and one of the more commonly available pigments. It is frequently recommended as a substitute for cadmium orange, but it is only slightly more transparent, and cadmium orange is more lightfast, darker valued, has a higher tinting strength, and is slightly more intense at the same hue (chroma of 92 compared to benzimidazolone's 86). Other useful substitutes are cadmium yellow deep (chroma 93), hansa yellow deep (96) and especially the transparent isoindolinone yellow R (PY110, chroma 93). See also the section on benzimidazolone pigments.

Pyrazoloquinazolone orange PO67 is a marginally lightfast, opaque, moderately staining, mid valued, very intense red orange pigment, offered by only two pigment manufacturers worldwide. Unrated by the ASTM and by Old Holland, my 2004 tests marginally assign it a "very good" (II) lightfastness, with a slight darkening in masstone and fading in tints after six weeks of sunlight exposure.

Old Holland coral orange is the only commercial source in watercolors; the paint blossoms easily but is inert wet in wet. The CIECAM J,a,b values for this pyrazoloquinazolone orange (PO67) were: 51, 68, 48, with chroma of 83 (estimated hue purity of 66) and a hue angle of 35.

CAUTION. This may be a useful paint for landscapes and florals, and is an interesting color by itself, but it does not seem to mix as effectively as perinone or cadmium orange, and its marginal lightfastness is not really worth risking. Substitutions: The color is not quite as intense as perinone orange, and can be easily matched by a mixture of perinone orange with a small amount of transparent burnt sienna (PR101).

lightfastness test sample

unexposed (top); exposed 800+ hours (bottom)

Isoindoline orange PO69 is an impermanent, opaque, moderately staining, mid valued, very intense red orange pigment, manufactured exclusively by BASF (Germany). Unrated by the ASTM, my 2004 tests assign it a "fair" (III) lightfastness, with slight darkening of the masstone color and significant fading in tint after six weeks of sunlight exposure (BWS 6). The CIECAM J,a,b values for this isoindoline orange (PO69) were: 55, 66, 52, with chroma of 84 (estimated hue purity of 68) and a hue angle of 38.

Old Holland scheveningen orange was the only commercial source in watercolor paints for this fugitive pigment, which has been reformulated as a mixture of perinone orange (PO43) and diarylide yellow (PY83). It was moderately active in wet applications, slightly brownish in masstone (but with a chroma of 85, it still appeared luminous) and with a yellower undertone. As with many Old Holland paints, the vehicle readily redissolved if rewetted, even along edges, which made the paint unusable for me.

AVOID. I don't consider this pigment stable enough for professional use; it is sufficiently lightfast only in masstone and has a relatively weak mixing strength. See also the section on isoindolinone pigments.

lightfastness test sample

unexposed (top); exposed 800+ hours (bottom)

Pyrrole orange PO71 is a lightfast, opaque, staining, moderately dark valued, very intense red orange pigment, manufactured exclusively by Ciba Specialty Chemicals (SZ). Unrated by the ASTM, my 2004 tests assign it "very good" (II) lightfastness with a slight tendency to darken in masstone. In watercolors PO71 undergoes a small drying shift, losing saturation by less than 15%.

Schmincke translucent orange is currently the only commercial source made with the pure pigment; it blossoms readily, with a subtle granulation, but is inert wet in wet. The CIECAM J,a,b values for this pyrrole orange (PO71) were: 50, 71, 46, with chroma of 85 (estimated hue purity of 68) and a hue angle of 33.

PO71 is very similar to pyrazoloquinazolone orange (PO67) which is more opaque and slightly less lightfast. See also the section on pyrrole pigments.

lightfastness test sample

unexposed (top); exposed 800+ hours (bottom)

TOP 40 PIGMENT Pyrrole orange PO73 is a lightfast, semitransparent, heavily staining, moderately dark valued, very intense red orange pigment, manufactured exclusively by Ciba Specialty Chemicals (SZ) as Irgazin DPP Orange. Unrated by the ASTM, my tests assign it "excellent" (I) lightfastness in watercolors. PO73 undergoes a small drying shift, losing saturation by less than 15%. The average CIECAM J,a,b values for pyrrole orange (PO73) are: 50, 75, 57, with chroma of 94 (estimated hue purity of 73) and a hue angle of 37.

Three paint brands now offer PO73 as a single pigment paint. All present an impressively rich, reddish orange hue, similar to perinone orange (PO43) but slightly more intense; it shifts toward red in undertone and appears salmon pink in tints, providing a healthy, subtle glow when glazed in flesh mixtures. Tinting strength is also high in all brands. Overall, the new Winsor & Newton winsor orange RS is slightly more intense (chroma of 98) and less staining than the other brands; the Rowney Artists paint is quite opaque and has a darker tone. When used in convenience mixtures, Holbein brilliant orange is opaque, heavily staining, mid valued, and also very intense (chroma 94); Rembrandt permanent orange is an equally intense mixture with benzimidazolone yellow that shifts strongly toward yellow in undertone.

I have very high regard for this pigment; it is everything modern pigment chemistry should be. Provided you use the transparent single pigment brands, this makes a very versatile and reliable paint, worth trying for florals and other brilliant painting styles, and splendid as a warm, almost pinkish tint or blush color for caucasian flesh tones. It is an ideal red orange pigment for the six paint secondary palette. See also the section on pyrrole pigments.

Several manufacturers opt to mix their orange paints with the "red" version of cadmium, PR108. Most of these mixed oranges are either yellower or redder than the typical orange hue. These manufacturers have opted not to use PO20 so that they can mix the hue to the exact color characteristics they require. Unlike the pure pigment cadmium oranges (listed under PO20), I have found slight lightfastness problems in some of these mixed oranges: typically, the yellow tone fades and the hue shifts slightly toward red. The average CIECAM J,a,b values for cadmium scarlet (PR108) are: 46, 80, 43, with chroma of 91 (estimated hue purity of 75) and a hue angle of 28.

Winsor & Newton makes their cadmium orange as a blend of the scarlet and yellow pigments, which gives their paint a yellower hue than any other cadmium oranges and a larger shift toward yellow in undertone. The Holbein cadmium red orange is a beautiful hue, just at the boundary between orange and scarlet, very similar to pyrrole orange (PO73): a good anchor for the warm side of the warm/cool color contrast. The Holbein cadmium yellow orange is also very intense (chroma of 98) with a hue close to a deep yellow. See also the section on cadmium pigments.

KEY TO THE PAINT RATINGS. Summarized as numbers: Tr = Transparency: 0 (very opaque) to 4 (transparent) - St = Staining: 0 (nonstaining) to 4 (heavily staining) - VR = Value Range: the value of the masstone color subtracted from the value of white paper, in steps of a 100 step value scale - Gr = Granulation: 0 (liquid texture) to 4 (granular) - Bl = Blossom: 0 (no blossom) to 4 (strong blossom) - Df = Diffusion: 0 (inert) to 4 (very active diffusion) - HA = Hue Angle in degrees of the CIELAB a*b* plane - HS = Hue Shift as the undertone hue angle minus the masstone hue angle, in degrees of the CIELAB a*b* plane - Lf = Lightfastness: 1 (very fugitive) to 8 (very lightfast) for paint in tint,full strength - Mentioned in pigment notes: Chroma: For the masstone paint on white watercolor paper. - Drying Shift: Change in masstone color appearance from a glistening wet to completely dry paint swatch, in units of lightness, chroma and hue angle in CIELAB. For more information see What the Ratings Mean.

Last revised 07.I.2015 • © 2015 Bruce MacEvoy