J. 0. S. A.

Color Characteristics of Artists' Pigments

NORMAN F. BARNESMassachusetts Institute of Technology, Cambridge, Massachusetts

(Received March 13, 1939)

AT the instigation of Dr. Herbert E. Ives, aninvestigation of the color of artists' pig-

ments was undertaken with the cooperation ofthe Department of Conservation and Researchof the Fogg Art Museum, Harvard University.A brief synopsis of the results of that investiga-tion are presented in this paper for the fifty-onepigment samples analyzed.

The method of preparation consisted, briefly,in dispersing the pigment particles in a bindingmedium and then covering a rag paper plaquewith successive paint coats until its surface wascompletely hidden. For the preparation of themedium a sizing material was made by cookingparchment cuttings with water and then de-

canting the liquor, which was cooled to a gel anddried. The medium was subsequently preparedfrom one part by weight of the dried parchmentsize to ten parts of water. The pigment in eachcase was hand-ground. Medium was added, thequantity of which was determined by the absorp-tion ratio of the pigment, such that a uniformworking consistency was obtained for all samples.In this process a practical minimum of vehiclewas used, a technique which gave a lean-vehicular paint structure; that is, the resultantfilm had a high pigment content and dried witha mat surface.

Listed in Table I will be found the pigmentswhich were analyzed, as well as their origin and

BLE I.

PIGMONT ORIGIN COMPOSITION

Red lead Artificial Lead oxide, Pb 3O4English vermilion Artificial Mercuric sulphide, HgSCadmium red Artificial Cadmium sulpho-selenide, CdS+CdSeMadder lake * OrganictAlizarin crimson Artificial OrganictCarmine lake * OrganictDragon's blood Natural OrganicRealgar Natural Arsenic disulphide, As2S2Venetian red Artificial Ferric oxide and calcium sulphate, Fe 2O3+CaSO 4Indian red Artificial Chiefly ferric oxide, Fe 2O3 , and some calcium sulphate, CaSO 4Cadmium orange, medium Artificial Cadmium sulphide, CdSGamboge Natural OrganicYellow ochre Natural Hydrous ferric oxide, Fe2 03*nH 2 0, plus alumina and silicaZinc yellow Artificial Zinc chromate, ZnCrO 4Indian yellow Natural OrganicSaffron Natural OrganicYellow lake (quercitron) Natural OrganictStrontium lemon yellow Artificial Strontium chromate, SrCrO4Hansa yellow 5 G Artificial OrganictChrome yellow, medium Artificial Lead chromate, PbCrO 4Cadmium yellow, light (cadmium lithopone) Artificial Cadmium sulphide, CdS+BaSO 4Orpiment Natural Arsenic trisulphide, As2S3Cobalt yellow Artificial Cobalt and potassium nitrites, CoK3(NO2)6-H 20Raw sienna Natural Chiefly oxide and hydrous oxide of iron and aluminum plus

silicaBurnt sienna Natural Chiefly oxides of iron and aluminum plus silicaRaw umber Natural Chiefly hydrous oxides of iron and manganeseBurnt umber Natural Chiefly oxides of iron and manganeseMalachite Natural Basic copper carbonate, CuC03 Cu(OH)2Chrome green, medium Artificial Chrome yellow mixed with Prussian blueVerdigris Artificial Basic copper acetate, Cu3(OH) 2(C 2H302 ) 4Emerald green Artificial Copper aceto-arsenite, Cu(C2H302)2-3CuAs2O4Terre verte Natural Iron, potassium and magnesium silicatesCobalt green Artificial Cobalt and zinc oxides, CoO-nZnOViridian Artificial Hydrous chromic oxide, Cr 2O 3 -2H20Cobalt blue Artificial Oxides of cobalt and aluminum, CoO -nA12 0 3Genuine ultramarine Natural Sodium aluminum silicate with sulphur plus calcite,

Na8_.oAoSi6O24 * S2±+CaCO3

208

MAY, 1939 V OL UM E 2 9

ARTISTS' PIGMENTS

TABLE I (Continued).

PIGMENT ORIGIN COMPOSITION

Cerulean blue Artificial Oxides of cobalt and tin CoO- nSnO2Azurite Natural Basic copper carbonate, 2CuCO3- Cu(OH)2Manganese violet Artificial Manganese phosphateCobalt violet Artificial Cobalt phosphate, Co3(PO4)2Smalt Artificial Silicate of cobalt and potassiumBlue verditer Artificial Basic copper carbonate, 2CuCO3 -Cu(OH)2French ultramarine blue Artificial Sodium aluminum silicate with sulphur, Na8-1oAl6Si6O24 S2 :4Indigo * OrganicPrussian blue Artificial Ferric ferrocyanide, Fe4[Fe(CN)6]3Titanium white A Artificial Titanium oxide, TiO2Titanium white B Artificial 75% barium sulphate, BaSO4, and 25% titanium oxide, TiO2Zinc white Artificial Zinc oxide, ZnOWhite lead Artificial Basic carbonate of lead, 2PbCO3-Pb(OH)2Lamp black Artificial Carbon, CIvory black Carbon plus calcium phosphate and carbonate, C+Ca3(PO4)2

+CaCO3

* This pigment comes from a natural source, but the process of preparation is so complex that it seems inaccurate to classify it as either naturalor artificial.

t The base on which the dye is struck is an inorganic white inert.* Most so-called ivory black sold in the artist trade today is bone black which is nearly identical in composition.

TABLE II.

TRISTIMULUS VALUES TRICHROMATIC COEFFICIENTS

PIGMENT X Y Z X y z

Red lead 47.19 32.76 8.73 0.5321 0.3695 0.0984English vermilion 34.96 22.26 10.04 0.5197 0.3309 0.1494Cadmium red 32.84 20.78 7.47 0.5375 0.3402 0.1223Madder lake 48.51 33.55 39.68 0.3985 0.2756 0.3259Alizarin crimson 11.67 6.61 3.48 0.5361 0.3038 0.1601Carmine lake 7.99 5.04 3.18 0.4929 0.3107 0.1964Dragon's blood 6.83 4.94 3.54 0.4460 0.3228 0.2312Realgar 42.17 32.35 12.11 0.4868 0.3734 0.1398Venetian red 17.71 13.12 7.08 0.4672 0.3462 0.1866Indian red 12.29 10.34 9.74 0.3797 0.3194 0.3009Cadmium orange, medium 51.94 42.18 4.90 0.5245 0.4260 0.0495Gamboge 34.14 29.87 4.89 0.4955 0.4335 0.0710Yellow ochre 43.77 41.15 16.81 0.4303 0.4045 0.1652Zinc yellow 78.05 82.57 13.37 0.4486 0.4746 0.0768Indian yellow 43.40 40.01 5.13 0.4902 0.4519 0.0579Saffron 34.40 33.45 9.28 0.4470 0.4345 0.1185Yellow lake 28.49 27.24 8.87 0.4410 0.4217 0.1373Strontium lemon yellow 74.10 84.36 19.80 0.4157 0.4732 0.1111Hansa yellow 5 G 66.51 75.09 7.97 0.4447 0.5020 0.0533Chrome yellow, medium 68.34 63.07 9.70 0.4843 0.4470 0.0687Cadmium yellow, light 71.58 76.66 10.83 0.4500 0.4819 0.0681Orpiment 65.55 64.45 16.40 0.4477 0.4402 0.1121Cobalt yellow 48.53 50.48 9.50 0.4472 0.4652 0.0876Raw sienna 22.33 20.03 7.19 0.4507 0.4043 0.1450Burnt sienna 9.62 7.55 4.96 0.4347 0.3414 0.2239Raw umber 7.66 7.44 5.05 0.3802 0.3693 0.2505Burnt umber 5.74 5.08 3.53 0.4000 0.3540 0.2460Malachite 34.97 41.77 42.84 0.2924 0.3493 0.3583Chrome green, medium 11.40 16.04 8.94 0.3133 0.4410 0.2457Verdigris 9.95 16.67 32.03 0.1696 0.2843 0.5461Emerald green 22.71 39.12 31.00 0.2446 0.4215 0.3339Terre verte 25.58 29.04 28.12 0.3092 0.3510 0.3398Cobalt green 13.97 19.99 25.78 0.2339 0.3346 0.4315Viridian 5.87 9.85 11.37 0.2167 0.3635 0.4198Cobalt blue 18.42 16.81 67.22 0.1798 0.1641 0.6561Genuine ultramarine 19.66 18.64 54.16 0.2126 0.2016 0.5858Cerulean blue 16.76 18.19 51.85 0.1931 0.2096 0.5973Azurite 9.51 9.26 27.34 0.2062 0.2008 0.5930Manganese violet 31.76 26.99 44.60 0.3073 0.2612 0.4315

209

NORMAN F. BARNES

TABLE II (Continued).

TRISTIMULUS VALUES TRICHROMATIC COEFICIENTS

PIGMENT X I Z y

Cobalt violet 14.44 9.34 27.49 0.2817 0.1821 0.5362Smalt 11.99 8.25 42.93 0.1898 0.1306 0.6796Blue verditer 16.62 16.46 54.46 0.1899 0.1880 0.6221French ultramarine blue 11.90 7.84 48.40 0.1747 0.1151 0.7102Indigo 4.22 3.62 5.43 0.3180 0.2728 0.4092Prussian blue 1.52 1.30 2.47 0.2883 0.2453 0.4664Titanium white A 93.50 95.75 110.02 0.3124 0.3199 0.3677Titanium white B 93.45 95.66 110.17 0.3122 0.3196 0.3682Zinc white 92.55 94.88 109.03 0.3122 0.3200 0.3678White lead 85.54 87.32 96.47 0.3176 0.3242 0.3582Lamp black 3.98 4.08 4.86 0.3081 0.3157 0.3762Ivory black 2.14 2.22 2.63 0.3055 0.3176 0.3769

chemical composition insofar as it is known.Many of the pigments can be obtained in boththe natural and the artificial form so that

TABLE III.

DOMINANTWAVE- RELATIVE EXCITA-LENGTH BRIGHT- TION(MILLI- NESS PURITY

PIGMENT MICRONS) (PERCENT) (PERCENT)

Red lead 596.6 32.8 73.8English vermilion 608.1 22.3 59.9Cadmium red 604.8 20.8 67.3Madder lake 496.5c 33.6 32.9Alizarin crimson 628.0 6.6 57.2Carmine lake 622.0 5.0 47.4Dragon's blood 610.2 4.9 38.1Realgar 593.0 32.4 62.6Venetian red 599.2 13.1 50.2Indian red 610.5 10.3 19.5Cadmium orange, medium 586.9 42.2 86.9Gamboge 584.0 29.9 81.2Yellow ochre 581.9 41.2 55.9Zinc yellow 575.8 82.6 79.7Indian yellow 581.6 40.0 84.8Saffron 579.6 33.4 68.4Yellow lake 580.6 27.2 63.4Strontium lemon yellow 572.3 84.4 70.4Hansa yellow 5 G 573.2 75.1 85.9Chrome yellow, medium 581.6 63.1 81.8Cadmium yellow, light 575.3 76.7 81.9Orpiment 579.1 64.4 70.2Cobalt yellow 576.5 50.5 76.8Raw sienna 584.2 20.0 61.3Burnt sienna 598.5 7.6 40.1Raw umber 581.5 7.4 33.0Burnt umber 589.5 5.1 34.2Malachite 515.2 41.8 6.6Chrome green, medium 552.4 16.0 34.7Verdigris 488.2 16.7 54.8Emerald green 511.9 39.1 22.8Terre verte 549.8 29.0 9.2Cobalt green 493.8 20.0 27.0Viridian 497.1 9.8 31.9Cobalt blue 474.6 16.8 65.5Genuine ultramarine 474.4 18.6 49.2Cerulean blue 478.9 18.2 54.5Azurite 475.6 9.3 51.3Manganese violet 553.7c 27.0 21.6Cobalt violet 560.3c 9.3 48.5Smalt 466.2 8.2 68.1Blue verditer 476.4 16.5 58.7French ultramarine blue 467.8 7.8 75.1Indigo 540.Oc 3.6 19.0Prussian blue 563.5c 1.3 24.4Titanium white A 565.5 95.8 1.5Titanium white B 570.0 95.7 1.4Zinc white 569.5 94.9 1.5White lead 576.7 87.3 4.1Lamp black 487.5 4.1 0.8Ivory black 494.5 2.2 1.7

designation in the table refers in such cases tothe actual pigment used.

The analysis was made through the use ofa recording photoelectric spectrophotometer.1 ' 2

The resultant spectrophotometric curves havebeen placed in interrelated groups and are shownin Figs. 1 to 4. The tristimulus values andtrichromatic coefficients have been computedusing I.C.I. Illuminant C, standard observer,and coordinate system and are to be found inTable II, while Table III includes the corre-sponding values of the dominant wave-length,relative brightness, and excitation purity of thesamples measured.

In order to give the reader an indication of

TABLE IV.

DOMINANT RELATIVE EXCITATIONWAVE-LENGTH BRIGHTNESS PURITY

PIGMENT (M;LLIMICRONS) (PERCENT) (PERCENT)

Emerald greenSample 1 511.9 39.1 22.8Sample 2 509.2 39.1 23.2Sample 3 509.2 38.8 22.9

Cerulean blueSample 1 478.8 18.2 54.5Sample 2 478.7 18.6 55.0Sample 3 478.7 18.1 54.9

Venetian redSample 1 599.2 13.1 50.2Sample 2 599.0 12.9 51.6Sample 3 599.0 13.2 50.7

1 A. C. Hardy, "A New Recording Spectrophotometer,"J. Opt. Soc. Am. 25, 305 (1935).

2 The samples were placed over a two-inch diameterhole in an eight-inch diameter integrating sphere whichwas coated on the inside with magnesium oxide. Theactual area measured was approximately circular and hada diameter of about one inch. The standard comparisonwhite was a freshly prepared magnesium oxide surface, asurface having a substantially nonselective reflectance of97.4 percent, according to J. S. Preston, "The ReflectionFactor of Magnesium Oxide," Trans. Opt. Soc. 31, 15(1929-30).

210

ARTISTS' PIGMENTS

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WAVE-LENGTH (mj.)

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WAVE-LENGTH (i)

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FIG. 1.

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C. YELLOW OCHRE A

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WAVE-LENGTH (mp)

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C. COBALT YELLOW

400 450 500 550 600 650 700WAVE-LENGTH (mp)

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400 450 500 550 600 650 700WAVE-LENGTH (mnu)

400 450 Soo 550 600 650 700WAVE-LEN GTH (mp)

FIG. 2.

212

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10 ~~~A.STRONTIUM LEMON YELLOW

C.CHROME YELLOW MEDIUM

ARTISTS', PIGMENTS

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WAVE-LENGTH (p)

xIA. COBALT BLUE

90 B. GENUINE ULTRAMARINEC. CERULEAN BLUED. AZURITE

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WAVE-LENGTH (mJu)

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FIG. 3.

100laA . MA NG AN E5E V IO L ET -

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400 450 500 550 600 650 700WAVE-LENGTH (mj)

213

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F. BARNES

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WAVE-LENGTH (m}j)

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xlvL 50 A. TITANIUM WHITEU B. TITANIUM WHITE & BARIUM SULPHATE 1:3z C. ZINC WHITE1-40_ D. LEAD WHITE( E. LAMP BLACK

LI F. IVORY BLACK

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, 30

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1c_ _ _ _ _ _ E ~~F _ _

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400 450 500 550 600WAVE-LENGTH (mn)

650 700

FIG. 4.

the precision of the results from the standpointof irregularities in the experimental technique, atable of comparative dominant wave-length,brightness and purity values has been preparedfor three samples of each of three pigmentspicked at random. For each group the sampleswere prepared using the same paint mixture andemploying the technique described earlier. Thefinal results of this comparison are given inTable IV.

The author wishes to express his sincereappreciation to Professor Arthur C. Hardy andto Mr. S. Q. Duntley for their helpful suggestionand to Mr. J. J. Hanlon for the integration ofthe curves. Special acknowledgment is given tothe research staff of the Fogg Art Museum forpreparing the samples for measurement, es-pecially to Mr. George L. Stout for his helpfulguidance in assisting this work.

214 NORMAN