Colour Analysis of Rembrandt Pastels - Colour Tools for ... · COLOUR ANALYSIS OF REMBRANDT PASTELS...

Colour Analysis of Rembrandt Pastels

Paul Centore

c© June 2, 2015

AbstractMunsell specifications, calculated from spectrophotometric measurements, are pre-

sented for the complete Rembrandt line of 218 artist’s pastels, produced by Royal Talensin Holland. The pastels’ hue, value, and chroma distributions are delineated. Tablesand figures are presented, that painters can use in making practical decisions aboutpastel employment and purchases. A list of duplicates (pairs of pastels whose namesare different but whose colours agree to within a CIE DE 2000 value of 2 or less) isgiven.

1 Introduction

A single manufacturer typically produces a few hundred pastels, of various colours. Thiswide variety is necessary because, unlike paints, pastels cannot be readily mixed to producelarge quantities of new colours. The variety, however, requires a significant organizationaleffort from both artists and manufacturers. The current document helps to provide thatorganization for one pastel brand, Rembrandt (produced by Royal Talens), by analyzingtheir line of 218 colours. The analysis is performed largely in terms of the Munsell coloursystem, whose concepts of hue (red, yellow, etc.), value (light vs dark), and chroma (dullvs saturated) are basic to painting. Tables and figures are presented, that should helpartists select Rembrandt pastels intelligently, both when painting and when purchasing.Purchasing is especially an issue for online or catalog sales, where the artist cannot see thepastels directly. The Rembrandt gamut is delineated in terms of hue, value, and chroma.Several pairs of duplicates, in which two different pastels produce very similar colours, arealso identified.

This report first describes the Rembrandt pastel line, and then describes the Munsellsystem, which will provide rigorous terms of reference for the pastel analysis. The analysisprocedure and results are given next, including tables and figures for practical use. Finally,an approach is suggested, involving contributions from painters and manufacturers, to extendthis analysis to further pastel brands

2 Description of Rembrandt Pastels

Rembrandt’s complete line consists of 218 pastels. This total includes fifteen dark pastelsthat were added in the last year. Currently, they can be purchased online in the United

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States from Dakota Pastels. The two major American art supply retailers, Jerry’s Artaramaand Dick Blick, do not yet stock the dark set, but Dick Blick at least has indicated that itwill be available soon. Rembrandt also offers a complete set of pastels containing 225 sticks.Over 20 of these 225, however, are duplicates. Furthermore, the complete set of 225 doesnot (as of September 2014) contain the 15 recently added dark pastels.

Rembrandt divides its pastels into 43 series, each of which consists of lighter and darkerversions of the same hue. A series is indicated by a three-digit number, such as 372, which is ared hue. After the three-digit number there is a comma, followed by another number. Whenthe second number is 5, the pastel contains a pure pigment. When the second number is lessthan 5, some amount of black (or perhaps another pigment) has been added to darken thecolour. When the second number is greater than 5, the colour has been lightened. The lowerthe second number, the darker the colour, and the higher the second number, the lighter thecolour. 372,2, for example is a dark reddish brown, while 372,10 is a pale orangish red.

3 The Munsell System

Albert Munsell devised his colour specification system for painters and visual artists. Itclassifies surface colours by three perceptual attributes that are basic to painting: hue, valueand chroma.

Hue is universally understood. It says whether a colour is red, yellow, purple, etc. Munselldesignates 10 basic hues: R (red), YR (yellow-red, or orange), Y (yellow), GY (green-yellow),G (green), BG (blue-green), B (blue), PB (purple-blue), P (purple), and RP (red-purple).Each basic hue is further subdivided into 4 steps, denoted with a numerical prefix. Forexample, the four greens are denoted 2.5G, 5G, 7.5G, and 10G. 2.5G is a yellower green,that is closer to GY than it is to BG. 10G is a bluer green, that is closer to BG than it is toGY. In all, then, the Munsell system specifies 40 hues (4 steps for each of the 10 basic hues).These 40 hues are equally spaced perceptually. One could interpolate any desired amountbetween two adjacent hues. For example, the hue 6GY is a yellowish green that is between5GY and 7.5GY, but closer to 5GY. White, black, and greys are not considered hues in theMunsell system. Rather, they are designated N, for “neutral.”

Many different colours can have the same hue. Figure 1, for example, shows the “hueleaf” for 6GY, a set of colours all of which have hue 6GY. The different colours within a hueleaf are specified further by value and chroma. The empty boxes indicate colours that arein the Munsell system, but that are beyond the gamut of the process used to produce thefigure. The hue leaf shades smoothly into the neutral axis, consisting of greys, shown on theleft.

Munsell value designates how light or dark a colour is. The theoretically darkest blackhas a value of 0, and is denoted N0. The theoretically lightest white has a value of 10, andis denoted N10. Between N0 and N10 are 9 progressively lighter greys, denoted N1 throughN9. The spacing between the greys is perceptually equal. All colours have a Munsell value,not just the neutrals. For example, there are light blues and dark blues. A blue with value8.5 has the same lightness as N8.5.

Munsell chroma refers to how intense, or saturated, a colour is. For example, a lemon isan intense yellow, while masking tape is a dull yellow. A dull colour is closer to a neutral

c© 2015 Paul Centore 2

COLOUR ANALYSIS OF REMBRANDT PASTELS

N2

N9

N8

N7

N6

N5

N4

N3

N1

2 4 6 8 10 12

Chroma

Hue: 6GY

Valu

e

Figure 1: The Hue Leaf for 6GY in the Munsell System

grey than an intense colour is. The Munsell system denotes chroma numerically. Greyshave chroma 0. A colour with a chroma of 10 or higher is generally perceived as saturated.Colours of low chroma, say 4 or less, are perceived as subdued, with a high grey content.

The Munsell notation for a colour takes the form H V/C, where H stands for hue, Vstands for value, and C stands for chroma. For example, the colour 10R 9/6 would be a verylight (V is 9), moderately intense (C is 6), orangish red (H is 10R). A colour with chroma 0is a neutral grey, which is denoted NV, where V stands for value. For example, N5 is a greythat is midway between white and black.

The Munsell system is important to painters for two reasons. First, the attributes itidentifies (hue, value, and chroma) are all vital to art. Second, the system provides a languageto communicate rigorously about colour. The 1943 Munsell renotation1 has standardizedthe calculation of hue, value, and chroma, from objective spectral measurements, so thatthese terms can be quantified. The standardization was based on a large number of colourjudgements made by about 40 human subjects, to insure that Munsell specifications areperceptually meaningful.

4 Analysis

4.1 General Procedure

The data set for this analysis consisted of 218 samples, comprising the complete line of pas-tels. Each sample measured about 1 inch square, and was applied by hand on white paper,in a layer that was opaque (or nearly so). The samples were measured three times with an X-Rite i1Pro2 spectrophotometer, using the M2 setting, and the final measurement was takento be the average of the initial three measurements. The output of a spectrophotometer

3 c© 2015 Paul Centore

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measurement is a sample’s reflectances, at intervals of 10 nm, from 380 to 730 nm. CIE xyYvalues2 were calculated for each sample, under the assumption of Illuminant C, which is theilluminant on which the Munsell system is standardized.1 The 1943 Munsell renotation1 pro-vides a look-up table from Munsell colours to xyY coordinates. An inversion algorithm3 wasused to find a Munsell specification for each pastel, from its xyY coordinates. Tables 1 and 2list these Munsell specifications. For researchers who would like to continue these investiga-tions further, the reflectance spectra and the Munsell specifications are available in the com-puter files RembrandtPastelsReflectanceSpectra.txt and RembrandtPastelsMunsellSpecifica-tions.txt, respectively, at the website www.99main.com/∼centore/ColourAnalysisOfPastels.

Measuring pastels can be difficult because of their uneven, dusty texture. Analysis ofi1Pro2 repeatability, when measuring pastels, revealed that the mean colour difference fromthe mean (MCDM), assuming Illuminant C and the 1931 Standard Observer, was slightlyover 1. Printed colours, by contrast, tended to have MCDMs that were about 0.25. Whenproducing printed reproductions of pastels, then, the largest source of variability is likelythat the colour of the pastel target is not known very well.

Figures 2 through 11 are a sort of inverse to Tables 1 and 2. These figures share thesame chroma and value axes that appear in Figure 1. Rather than referring to a singlehue, however, each of Figures 2 through 11 refers to a range of hues, which share the sameMunsell letter designation. Figure 2, for example, shows all pastels whose hue is between 0Rand 10R, so a pastel of hue 3.2R could appear alongside a pastel of hue 9.6R. Each pastel ina figure is placed at coordinates given by its chroma and value, as in Figure 1. If multiplepastels with the same hue letter designation (but not necessarily the same numerical hueprefix) also have the same chroma and value, then those pastels are displayed in a sequence,separated by slashes.

Painters can use Figures 2 through 11 to determine which Rembrandt pastels have, atleast approximately, the desired hue, value, and chroma. Informed choices can then bemade when executing a painting. In addition, the figures can aid in purchasing decisions.Typically, colour reproductions in art supply catalogs, either in paper or online, are notaccurate enough for confident purchasing decisions, especially given the wide gamut pastelscan cover. The figures should provide a better basis for an artists to decide which pastelswill be most helpful.

4.2 Hue, Value, and Chroma Distributions

Figures 12 through 14 are histograms of the entire Rembrandt line in terms of hue, value,and chroma. Figure 12 shows that the Rembrandt pastels do not cover the entire gamut ofhues evenly. There are about twice as many pastels in the hues between 5R and 5Y, as thereare in the rest of the hues. Human skin tones mainly cluster around R, YR, and Y, so thispredominance would provide fine colour distinctions for portrait or figure painting. There isa noticeable lack of coverage around the greens and blue-greens, with only five pastels fallingin the hue BG.

Figure 13 gives the overall Munsell value distribution of the pastels. The bulk of thepastels fall between values 2 and 9, with relatively few very dark or very light pastels.Tables 3 and 4 list the five darkest and five lightest pastels. The darkest pastels tend tohave values near 2. This minimum should be compared with oil or acrylic paints, in which



the darkest blacks tend to have values near 1, a full value step darker than the darkestRembrandt pastels. Many of Rembrandt’s darkest pastels are recent additions, from thenew set of darks. In fact, eight of the fifteen darkest pastels (235,2; 347,2; 506,2; 508,2;536,2; 620,2; 627,2; 640,2) are from that set. Very dark pastels tend toward dullness, butthe Prussian blues in the 508 series have relatively high chromas.

The lightest pastels tend towards neutrality, and also do not reach the extremes routinelyachieved by oil and acrylic paints. Titanium white, for example, which is the standard artist’s


PAUL CENTORE

100,5 3.7Y 9.1/0.6 235,2 6.4YR 2.8/2.2 370,3 0.3YR 4.0/5.8101,5 5.4Y 9.1/0.5 235,3 3.1YR 4.0/4.8 370,5 8.3R 5.2/12.2201,3 0.5GY 6.1/5.7 235,5 0.5YR 5.9/12.1 370,7 9.1R 5.7/11.7201,5 6.2Y 8.4/10.5 235,8 5.3YR 7.4/7.9 370,9 1.2BG 5.8/2.9201,7 8.0Y 8.5/7.8 235,9 1.6YR 7.2/7.3 371,3 5.0R 3.3/6.2201,8 8.6Y 8.6/5.5 236,3 8.1YR 5.5/8.5 371,5 5.8R 4.0/12.7202,3 5.7Y 5.4/5.8 236,5 7.2YR 2.8/3.0 371,7 2.4R 5.2/11.2202,5 1.2Y 7.7/11.4 236,7 9.9YR 3.9/3.5 371,8 0.8R 7.2/6.5202,7 4.2Y 8.3/9.1 236,8 0.6Y 5.1/3.4 371,9 1.6R 8.0/3.5202,9 3.8Y 8.7/3.0 236,9 9.9YR 5.2/4.3 372,2 0.7YR 2.9/2.8202,12 4.1Y 8.9/1.1 318,3 5.6YR 5.3/4.1 372,3 9.4R 3.2/4.7205,3 0.4GY 6.7/7.1 318,5 4.4R 4.7/11.9 372,5 7.2R 4.4/12.6205,5 0.3GY 8.6/10.0 318,7 2.6R 5.6/11.4 372,8 7.5R 6.8/7.2205,8 0.6GY 8.5/6.2 318,8 2.2R 6.9/7.1 372,9 9.7R 7.7/4.6205,9 0.8GY 9.0/4.0 318,9 2.5R 7.4/6.3 372,10 3.0YR 8.4/2.7205,12 6.9Y 9.1/0.9 331,3 3.8R 3.8/5.5 397,3 4.9RP 3.9/7.8227,2 7.7Y 4.7/2.2 331,5 4.9R 3.8/11.1 397,5 6.3RP 4.6/11.4227,3 3.0Y 5.7/4.4 331,7 0.8R 5.3/10.1 397,7 4.7RP 5.2/10.6227,5 0.9Y 7.2/7.5 331,8 9.2RP 6.7/8.4 397,9 4.4RP 7.1/6.2227,7 1.7Y 8.2/4.7 331,9 0.7R 8.4/2.7 397,10 0.8R 8.2/2.9227,9 3.4Y 8.7/2.2 339,3 3.3YR 4.3/2.4 408,2 4.3Y 2.7/0.9227,10 3.4Y 8.9/1.8 339,5 1.2YR 6.3/6.6 408,3 1.9Y 3.6/1.8231,3 7.6YR 5.5/4.7 339,7 2.7YR 7.3/4.5 408,5 2.1Y 4.2/2.7231,5 6.0YR 6.2/7.7 339,8 0.6YR 7.7/3.2 408,7 1.8Y 5.1/3.2231,7 6.1YR 7.0/7.5 339,9 2.6YR 8.2/2.2 408,9 3.9Y 6.3/2.2231,8 6.7YR 7.6/5.8 339,10 3.4YR 8.5/1.5 408,10 3.1Y 6.9/2.1231,9 9.0YR 8.2/3.5 343,3 8.4R 3.7/5.7 409,3 6.0YR 2.9/1.5231,10 9.4YR 8.6/2.4 343,5 8.2R 3.8/6.7 409,5 1.6YR 3.3/3.0234,2 3.7Y 4.1/2.0 343,7 7.0R 4.9/6.0 409,7 4.8YR 4.4/3.5234,3 1.0Y 5.2/4.3 343,8 7.3R 7.1/4.5 409,8 5.5YR 6.3/3.7234,5 9.3YR 6.7/7.2 343,9 7.7R 7.1/4.5 409,9 7.9YR 7.2/3.2234,7 9.7YR 7.0/6.1 347,2 7.9R 2.5/1.7 409,10 8.3YR 8.0/2.0234,8 0.8Y 7.5/5.3 347,3 3.4R 2.9/3.4 411,3 3.1YR 3.4/3.5234,9 1.1Y 7.9/4.0 347,5 7.3RP 3.7/6.2 411,5 0.6YR 4.6/8.3234,10 9.9YR 8.0/3.1 347,7 2.5R 5.5/4.7 411,7 2.3YR 5.6/8.5

347,9 2.7R 7.7/2.6 411,8 3.6YR 6.4/7.3411,9 7.4YR 7.7/4.0411,10 8.7YR 8.3/2.7

Table 1: Munsell Specifications for Rembrandt Pastels (Series 100 through 411)



505,3 2.6PB 4.2/4.2 548,2 0.9P 3.0/1.6 633,3 2.7GY 6.1/6.1505,5 5.5PB 4.6/12.4 548,3 1.8P 3.6/2.7 633,5 1.9GY 7.9/9.4505,7 5.2PB 5.0/11.3 548,5 3.3P 4.7/8.2 633,7 1.7GY 8.3/7.2505,8 2.9PB 6.9/5.4 548,7 3.5P 6.2/5.9 633,9 1.7GY 8.5/4.6505,9 2.3PB 8.2/2.0 548,8 3.2P 7.0/3.6 640,2 8.5BG 2.4/1.6505,10 7.5B 8.6/0.7 570,3 9.2B 3.7/6.7 640,3 7.4BG 3.3/3.4506,2 4.2PB 2.8/3.8 570,5 1.6PB 4.2/10.1 640,5 8.1BG 3.9/6.5506,3 5.3PB 2.9/5.8 570,7 9.2B 6.5/6.7 640,7 8.1BG 5.2/7.2506,5 5.9PB 3.5/12.6 570,9 3.9B 7.9/2.8 640,9 6.9BG 6.5/6.3506,7 6.4PB 5.5/10.4 618,3 5.6GY 5.4/4.1 675,3 2.5G 4.7/5.9506,9 3.0PB 7.7/2.7 618,5 9.7GY 7.2/9.9 675,5 3.2G 6.1/11.2508,2 2.7PB 2.0/3.0 618,8 9.0GY 7.7/5.5 675,8 3.4G 7.7/6.1508,3 4.3PB 2.2/4.9 618,9 7.1GY 8.0/4.4 700,5 9.1G 1.7/0.4508,5 5.1PB 2.5/6.3 619,3 5.4G 4.3/4.4 704,3 4.1Y 2.7/0.3508,7 3.2PB 3.7/7.9 619,5 6.0G 5.2/7.9 704,5 2.5Y 4.1/0.4508,8 0.7PB 5.6/6.7 619,7 4.9G 5.9/7.5 704,7 3.4Y 6.0/0.5522,2 4.8B 3.3/2.8 619,9 1.8G 8.1/2.6 704,8 2.9Y 6.8/0.5522,3 4.2B 3.9/5.7 620,2 9.5Y 2.9/2.0 704,9 4.8Y 7.7/0.3522,5 5.2B 5.2/8.1 620,3 9.6Y 3.7/3.1 704,10 2.8Y 8.3/0.5522,8 2.9B 7.0/6.1 620,5 0.1GY 4.5/5.1 707,3 8.2PB 3.2/0.9522,10 1.3B 8.1/2.9 620,7 9.5Y 6.0/6.2 707,5 9.8PB 3.9/1.2536,2 3.3P 2.8/2.2 620,8 3.3GY 6.8/5.3 707,7 8.4PB 5.1/1.3536,3 4.6P 3.6/5.2 620,10 9.6Y 8.4/1.7 707,8 6.1PB 6.6/0.8536,5 5.7P 3.4/7.8 626,3 6.6GY 3.4/3.3 707,9 6.5PB 7.2/0.4536,7 7.5P 5.2/8.8 626,5 5.6GY 5.3/6.9 707,10 4.0Y 7.8/0.1536,9 3.0RP 7.6/2.5 626,7 4.2GY 6.2/7.7 709,3 2.1G 3.5/0.9538,3 9.6R 2.6/1.6 626,9 5.0GY 7.7/6.4 709,5 9.3GY 3.8/1.2583,5 9.8R 2.7/2.6 626,10 3.8GY 8.1/3.9 709,7 0.9G 5.6/1.0538,7 5.4R 4.3/3.1 627,2 1.2G 2.8/2.2 709,8 0.6G 6.8/0.6538,8 4.8R 5.5/2.6 627,3 1.7G 3.5/3.2 709,9 7.9GY 7.6/0.5538,9 0.0R 6.5/2.3 627,5 4.4G 4.1/5.0 709,10 5.5GY 8.2/0.5538,10 2.2R 7.7/1.1 627,7 4.4G 4.5/5.9 727,3 0.8PB 3.2/1.6545,2 2.0RP 3.0/2.1 627,8 6.0G 5.7/6.9 727,5 2.3PB 4.3/1.7545,3 0.5RP 3.6/12.2 627,9 3.6G 7.2/5.1 727,7 3.5PB 5.8/1.5545,5 2.4RP 4.5/15.3 627,10 3.5G 7.8/3.2 727,8 0.7PB 6.6/0.4545,7 1.8RP 5.4/13.6 727,9 0.7PB 7.2/0.8545,8 3.1RP 7.5/6.6 727,10 4.8G 7.9/0.1

Table 2: Munsell Specifications for Rembrandt Pastels (Series 505 through 727)


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

318,5

318,9

331,3 331,5

331,7

331,9

343,3

343,5

343,7

347,2

347,3

347,7

347,9

370,5

371,3

371,5

371,7

371,8

371,9

372,3

372,5

372,8

372,9

397,10

538,3538,5

538,7

538,8

538,9

538,10

343,8/343,9318,8

318,8

318,7/370,7

Figure 2: Rembrandt Pastels of Munsell Hue R



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

231,3

231,5

231,7

231,8

231,9

231,10

234,5

234,7

234,10

235,2

235,3

235,5

235,8

235,9

236,3

236,5

236,7

236,8

236,9

339,3

339,5

339,7

339,8

339,9

339,10

370,3

370,9

372,2409,3

409,5

409,7

409,8

409,9

409,10

411,5

411,8

411,9

372,10411,10

411,7

411,3

Figure 3: Rembrandt Pastels of Munsell Hue YR


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2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

201,5201,7

201,8

202,3

202,5

202,7

202,9

227,2

227,3

227,5

227,7

227,9

234,2

234,3

234,8

234,9

408,3

408,5

408,7

408,9

408,10

620,2

620,3

620,7

620,10

704,3

704,5

704,7

704,8

704,10

100,5/101,5205,12

202,12/227,10

707,10

408,2

Figure 4: Rembrandt Pastels of Munsell Hue Y



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

205,3

205,5205,8

205,9

618,3

618,5

618,8

618,9

620,5

620,8

626,3

626,5

626,7

626,9

626,10633,5

633,7

633,9

709,5

709,9

709,10

201,3/633,3

Figure 5: Rembrandt Pastels of Munsell Hue GY


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2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

619,3

619,5

619,7

619,9

627,2

627,3

627,5

627,7

627,8

627,9

627,10

675,3

675,5

675,8

700,5

709,3

709,7

709,8

727,10

Figure 6: Rembrandt Pastels of Munsell Hue G



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

640,2

640,3

640,5

640,7

640,9

Figure 7: Rembrandt Pastels of Munsell Hue BG


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

505,10

522,2

522,3

522,5

522,8

522,10

570,3

570,7

570,9

Figure 8: Rembrandt Pastels of Munsell Hue B



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

505,3

505,5

505,7

505,8

505,9

506,2506,3

506,5

506,7

506,9

508,2

508,3

508,5

508,7

508,8

570,5

707,3

707,5

707,7

727,5

727,7

727,8

707,9/727,9

707,8

727,3

Figure 9: Rembrandt Pastels of Munsell Hue PB


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

536,2

536,3

536,5

536,7

548,2

548,3

548,5

548,7

548,8

Figure 10: Rembrandt Pastels of Munsell Hue P



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Mu

nsell

Valu

e

Munsell Chroma

331,8

347,5397,3

397,5

397,7

397,9

536,9

545,2

545,3

545,5

545,7

545,8

Figure 11: Rembrandt Pastels of Munsell Hue RP


PAUL CENTORE

0

5

10

15

20

25

30

35

40

10RP 10R 10YR 10Y 10GY 10G 10BG 10B 10PB 10P 10RP

NumberofPastels

Munsell Hue

Figure 12: Hue Histogram of Rembrandt Pastels

white today, has a value of about 9.8, while the lightest Rembrandt pastels only reach 9.1,nearly a full value step lower. In general, then, Rembrandt pastels have a restricted valuerange, when compared to paints.

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10

Num

ber

of

Paste

ls

Munsell Value

Figure 13: Value Histogram of Rembrandt Pastels

Figure 14 is a histogram of the chromas of Rembrandt pastels. The chromas peak atjust over 2, and taper off steadily, reaching a maximum around 15. Very intense colours,with chromas of 10 or above, attract attention, so most artists tend to use them sparingly,



Pastel Munsell Specification Munsell Value700,5 9.1G 1.7/0.4 1.7508,2 2.7PB 2.0/3.0 2.0508,3 4.3PB 2.2/4.9 2.2640,2 8.5BG 2.4/1.6 2.4508,5 5.1PB 2.5/6.4 2.5

Table 3: Darkest Rembrandt Pastels

Pastel Munsell Specification Munsell Value100,5 3.7Y 9.1/0.6 9.1101,5 5.4Y 9.1/0.5 9.1205,12 6.9Y 9.1/0.9 9.1205,9 0.8GY 9.0/4.1 9.0202,12 4.1Y 8.9/1.1 8.9

Table 4: Lightest Rembrandt Pastels

as accents. The bulk of the colours in a painting are usually of low or moderate chroma, sothe Rembrandt pastel line fits this pattern. Tables 5 and 6 list the five least and five mostsaturated Rembrandt pastels. The pastels in Table 5 all have chromas of 0.5 or less, so theyare very neutral greys. The very intense pastels in Table 6, and in fact 12 of the 15 mostintense pastels, all have similar hues, clustering around reds and purples. Their values arealso similar, around 4 or 5, so there is not much variety in the highly saturated pastels.

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12 14 16 18 20

Num

ber

of

Paste

ls

Munsell Chroma

Figure 14: Chroma Histogram of Rembrandt Pastels


PAUL CENTORE

Pastel Munsell Specification Munsell Chroma707,10 4.1Y 7.8/0.2 0.2727,10 4.8G 7.9/0.2 0.2704,3 4.1Y 2.7/0.3 0.3704,9 4.8Y 7.7/0.3 0.3707,9 6.5PB 7.2/0.4 0.4

Table 5: Least Saturated Rembrandt Pastels

Pastel Munsell Specification Munsell Chroma545,5 2.4RP 4.5/15.3 15.3545,7 1.8RP 5.4/13.6 13.6371,5 5.8R 4.0/12.7 12.7372,5 7.2R 4.4/12.6 12.6506,5 5.9PB 3.5/12.6 12.6

Table 6: Most Saturated Rembrandt Pastels

4.3 Duplicates

In addition to Munsell characteristics, colour differences between pastels were also analyzed.The CIE DE 2000 difference formula,2,4 commonly abbreviated ∆E00, was used. This formuladepends on an illuminant, so Illuminant C, which is specified in the Munsell renotationstandard, was used in calculations. The lower the ∆E00, the more similar two coloursare. When the ∆E00 of two colours is low enough, even if it is not 0, the two colours areindistinguishable. It is not always clear how low ∆E00 should be for indistinguishability, buta cutoff of 2 was used for this analysis. ∆E00 values were calculated for every possible pairof Rembrandt pastels.

First Pastel Second Pastel Difference (∆E00)343,8 343,9 0.4100,5 101,5 0.6704,9 707,10 1.2235,8 236,8 1.5347,2 538,3 1.5707,8 727,8 1.6318,3 343,5 1.8231,9 234,10 1.8707,10 727,10 1.9331,9 397,10 1.9372,2 538,5 2.0

Table 7: Duplicate Pairs of Rembrandt Pastels

Table 7 shows all pairs, 11 in total, whose ∆E00 was 2 or less. Figure 15 is a photographof the pairs of duplicate pastels, side by side for comparison. A painter can verify for himself



Figure 15: Side-by-side Comparison of Rembrandt Pastels of Similar Colour

that these pairs are duplicates (or nearly so), by applying the two pastels in a pair, in thicklayers, adjacent to each other. This document’s final page, which was used for Figure 15,can be printed out to make a convenient template for these comparisons. It will usuallybe difficult to tell where one colour stops and the other colour starts. From a practicalpoint of view, a painter would not need to purchase one of the pastels in each pair. Themanufacturer could similarly replace one of the pastels in each pair with a brand new colour,thus extending the line’s gamut without increasing the number of pastels produced.

The results in Table 7 are subject to two major possible sources of error: measurementvariability and manufacturing variability. Measurement variability, in particular the highMCDM, has already been discussed. Manufacturing variability refers to the fact that thesame pastel might have a slightly different colour when produced in different batches or atdifferent times. Figure 16 shows a particularly clear example. Two pastels, both labeled331,9, have very different colours. The duplicate listed in Table 7 occurs when the left-handversion of 331,9 is used, but there is no duplication when the right-hand version is used. Asimilar situation holds for Pastel 343,8, which also seems to have multiple versions. It islikely that there was some reformulation of the colours between the times these two pastelswere produced.

This inconsistency poses difficulties for painters. Pastels have a long shelf life, and usuallyexcellent colourfastness. A painter could profitably use pastels that are several decades old;indeed, some of the pastels analyzed in this report could have been produced that long ago.In such cases, colour guides like the ones presented here could be misleading, or simply wrong.Manufacturers could avoid this situation, and make their nomenclature more meaningful, ifthey used a colorimetric standard such as the Munsell system to name pastels.


PAUL CENTORE

Figure 16: Two Different Colours for Pastel 331,9

5 Other Pastel Brands

The current document has analyzed only one pastel manufacturer, Rembrandt. A previousstudy5 has analyzed another pastel manufacturer, Unison. Comparative studies involvingother manufacturers would be even more helpful to pastel artists. The calculations, in-cluding the production of this document’s histograms, plots, and tables, have been largelyautomated, using code written for Octave or Matlab. The measurements are straightforwardand reasonably quick, once samples are available. A sample in this context is not the pastelitself, but rather a piece of paper to which the pastel has been applied.

The current bottleneck is obtaining samples. While the author owns several hundredpastels from many brands, he has no complete line from any one brand. Other pastel artists,who do have complete sets, are invited to contribute to further pastel analysis by sendingthe author samples, which he can measure and analyze.

The samples should meet the following conditions:

1. Each sample should be at least half an inch (or 1.5 centimeters) by half an inch,

2. The samples should be applied to a white or near-white standard pastel paper. CansonMi-Teintes paper is adequate, but sanded papers, such as Wallis or Sennelier LaCarte,work well, too,

3. The pastels should be applied thickly enough that the samples are opaque. When indoubt, add more pastel to a sample. Ideally, it should be impossible to discern thecolour of the paper through the pastel sample,

4. The surface of the samples should be reasonably smooth, with no obvious irregularities.Rubbing the pastel with a finger produces a sufficient finish,

5. The samples should be clearly labelled, using the pastel manufacturer’s naming con-vention,



6. Do not use any fixative, as this can alter colours. A protective sheet of Glassine canbe used over each sheet of samples, to keep the pastel from rubbing off,

7. For ease of measuring with the i1Pro2 spectrophotometer, the sheets with the samplesshould be no wider than 12 inches, and

8. There is no problem using a large number of smaller sheets (say 8.5 by 11 inches), foreasier shipping.

Once the samples are prepared, they can be mailed to the author, Paul Centore, at 62Chicago Ave., Groton, Connecticut 06340, USA, who will measure them, and prepare areport, similar to this one, that he will post on his website. Artists should be aware thatpreparing samples can be considerably more time-consuming and tedious than it seems,especially since it is important to produce a thick, opaque layer. An entire set of samplescan take eight hours or more, depending on the number of pastels.

Apart from artists, pastel manufacturers are also invited to send samples of their lines.If preparing samples is too tedious, then the manufacturer can send a complete set of pastelsto the author, who will prepare the samples himself, and generate a report. In addition toproviding some exposure, the report might also dentify unexpected duplicates, or gaps ingamut coverage. This information can help revise and further develop the pastel line.

References

1. Sidney Newhall, Dorothy Nickerson, & Deane B. Judd. “Final Report of the O. S. A.Subcommittee on the Spacing of the Munsell Colors,” JOSA, Vol. 33, Issue 7, 1943, pp.385-418.

2. CIE. “Colorimetry.” Vienna: CIE Technical Report No. 15:2004, 3rd ed., Central Bureauof the CIE; 2004.

3. Paul Centore, “An Open-Source Inversion Algorithm for the Munsell Renotation,” ColorResearch & Application, Vol. 37, No. 6, December 2012, pp. 455-464.

4. Gaurav Sharma, Wencheng Wu, & Edul N. Dalal, “The CIEDE2000 Formula: Imple-mentation Notes, Supplementary Test Data, and Mathematical Observations,” COLORResearch and Application, Vol. 30, Number 1, February 2005, pp. 21-30.

5. Paul Centore, “Colour Analysis of Unison Pastels,” February 2014, available at the web-site www.99main.com/∼centore/ColourAnalysisOfPastels.


Rembrandt Pastels: Near-Duplicates

343,8 343,9

DE0.4

100,5 101,5

DE0.6

704,9 707,10

DE1.2

235,8 236,8

DE1.5

347,2 538,3

DE1.5

707,8 727,8

DE1.6

318,3 343,5

DE1.8

231,9 234,10

DE1.8

707,10 727,10

DE1.9

331,9 397,10

DE1.9

372,2 538,5

DE2.0

Copyright 2015 Paul Centore 1. www.99main.com/~centore

*

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*This number has been assigned to two different colours, only one of which produces a duplicate.

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