pigmented colorants: dependence on media and time - Cornell ...

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pigment. A five-digit number follows the generic name and number, indicating the chemical composition of each colorant, if known (some pigments have no number, as their exact chemical structures are proprietary). As an example, the full color index for Titanium Dioxide white is PW 6 (77891). A more complete discussion of the color index is found in [Ber00]. Ultimately, while many of the major art manufacturers today are honest in their labeling, the practice is not universal, and certainly was not so in the past. Thus, one must still proceed critically even when paint labels list a particular hue or when artists document the palettes they use. As paints are predispersed by suppliers of artists’ materials, there is always the possibility of extraneous additives in paint. Mislabeling, synthetic materials, and other substances can all affect the resulting appearance if a pigment in solution. As such, in our research to study the affects of varying binding media over time, we agreed that it was imperative to create all of the paints by hand, rather than purchase premade tube paint. This ensures that only the purest materials went into each paint, eliminating any outside factors. In this manner, the exact same pigments of pure composition are used in the different media. This also ensures that our paints are only made from pigment and binder. There are no inert fillers to dilute pigments, affecting the pigment volume concentration, nor are there materials that affect the chroma or lightness of the hue. 5.1.2 Pigments With the many <strong>colorants</strong> available to the modern painter, if is difficult for an artist to choose a finite palette that comprises a sufficient variety to fulfill all of his/her 141 color requirements. The choice typically depends on the artist’s preference and
the requirements of the work at hand. A palette that contains less than a dozen colors can be considered a simplified palette, while more than fourteen would be an elaborate palette. Successful painting can be done with a very limited palette, and there are some advantages to doing so. Painters typically receive training with simplified palettes as a matter of discipline; this enforces a sort of color harmony, as hues in a work are derivatives of one another. However, in the majority of cases, it is generally beneficial to have a range of colors available. Single pigment colors are invariably purer than mixtures that imitate them. The pigments chosen in our work are an attempt to maintain a typical artist’s palette, which maximizes the gamut of colors available, while minimizing the amount of pigments that needed to be studied. Neither artists nor scientists wish to perpetuate a excessively large number of unessential items to paint with or study. The author (originally trained as an artist) chose a representable portion that spans Mayer’s hue designations in his modern approved list of pigments [May80]. While there may be other (possibly superior) pigments available, each is long established as a useful colorant tool and has its own individual characteristics. There are many sources of pure pigments available, including Kremer Pigments (New York) and Sinopia Pigments (San Francisco). For our research, we decided on Rublev Pigments from Natural Pigments (Willits, CA). This line contains a wide variety of naturally occurring earth colors, which were available to historical painters long before the commercial manufacture of artificial pigments. Earth colors also tend to have a very high permanence and lightfastness rating. While synthetic variants have approximated many of these <strong>colorants</strong>, many still hold a permanent spot in artists’ palettes and have done so for thousands of years. The 142 <strong>colorants</strong> were also chosen such that they were compatible with the many different
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PIGMENTED COLORANTS: DEPENDENCE ON
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ABSTRACT We present a physically ba
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Acknowledgements This work would no
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Table of Contents 1 Introduction 1
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List of Tables 2.1 Average pigment
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3.15 Photoreceptor absorption .....
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B.15 Variation of spectral reflecta
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corrode the surfaces of materials.
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Figure 1.1: Detail of the Azor-Sado
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However, since mural artwork is typ
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at a very high quality (albeit limi
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heterogeneous sum of very different
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which linseed oil derives (the most
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oration of a rigidly painted layer
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ing will hit the ground and reflect
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tion of paint tubes in 1841 and the
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Figure 2.8: Natural pigments of ant
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ecome more common recently. The Ame
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A V = O(r2 ) O(r3 ) = 1 O(r) 24 (2.
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Table 2.2: Pigment specific gravity
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provide the underlying color to a p
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though the speed of light in air is
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In general, when light travels from
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materials while lit from behind. Li
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Table 2.4: Index of refraction η f
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to completely congeal. Hence, these
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ond together to form proteins. Exam
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to its original state by any means.
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While it has been used since the 19
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organic binder found in more conven
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3.1.1 Visible Light Spectrum Light
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Figure 3.2: Hue, brightness and sat
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measures how much light is reflecte
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Figure 3.6: Additive color mixing o
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Figure 3.9: The physical amount of
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The vascular tunic lies on the wall
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Figure 3.11: Cross section of the r
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Not all areas have the same sensiti
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identify and distinguish between va
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that range between zero and full in
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spectrum. This insures that the res
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Figure 3.19: Graphical representati
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X x = (X + Y + Z) Y y = (X + Y + Z)
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color into the appropriate RGB colo
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components in the image (the smalle
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haviors of subtractive mixing and i
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of perceptually equal sizes. Unfort
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enabling one to transform between t
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andwidth as converted signals are s
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Figure 3.28: Retinal ganglion recep
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example shown in Figure 3.28. Under
Page 103 and 104: Figure 3.31: The work of Josef Albe
Page 105 and 106: sensations for each trial and picke
Page 107 and 108: Chapter 4 Previous Work There is no
Page 109 and 110: different location. Subsurface scat
Page 111 and 112: describes the scattering and absorp
Page 113 and 114: only accounts for a small percentag
Page 115 and 116: σ ′ t = σa + σ ′ s and α
Page 117 and 118: 104 Figure 4.4: A model of an alaba
Page 119 and 120: effects or are too computationally
Page 121 and 122: 108 Figure 4.6: Results using Kubel
Page 123 and 124: specifying pigments works adequatel
Page 125 and 126: color representation, it is not fea
Page 127 and 128: time. A metallic surface patina is
Page 129 and 130: the system consisted of wetness and
Page 131 and 132: or darkening enables the museum per
Page 133 and 134: in front of a displayed work. Felle
Page 135 and 136: light exposure. This effect is espe
Page 137 and 138: over time. Perceptually, these hues
Page 139 and 140: The rate of change of the concentra
Page 141 and 142: over white grounds) suffer the grea
Page 143 and 144: protects the deeper remaining color
Page 145 and 146: light source. This method is used w
Page 147 and 148: chemical smog and have been identif
Page 149 and 150: Chapter 5 Preparation & Measurement
Page 151 and 152: tending transparent pigments used i
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Page 157 and 158: 144 Figure 5.2: Left: Magnified vie
Page 159 and 160: Table 5.2: Relevant data regarding
Page 161 and 162: historically one of the best grades
Page 163 and 164: created far too strong of a binder,
Page 165 and 166: too brittle and cracking. While wor
Page 167 and 168: 154 Figure 5.4: Reflectance values
Page 169 and 170: 5.1.5 Painting After the layers of
Page 171 and 172: The gray card reflected 18% of the
Page 173 and 174: 160 Figure 5.8: The optical setup f
Page 175 and 176: Note that harmonics reflect at the
Page 177 and 178: Note that the calibration factors f
Page 179 and 180: Chapter 6 Experimental Results 6.1
Page 181 and 182: 168 Figure 6.1: Lapis Lazuli in dif
Page 183 and 184: (such as CIE standards C, D50, orD6
Page 185 and 186: 172 Table 6.2: Perceptual differenc
Page 187 and 188: 174 Figure 6.3: Munsell plots of La
Page 189 and 190: and j has a saturation of red rsat,
Page 191 and 192: 178 Figure 6.4: Variation of spectr
Page 193 and 194: visible spectrum are increasing at
Page 195 and 196: 182 Figure 6.5: Munsell plots of La
Page 197 and 198: trying to match color ca from the p
Page 199 and 200: as it ages. This is in direct contr
Page 201 and 202: teractive viewer. In our applicatio
Page 203 and 204: 190 Figure 7.1: Our simulated canva
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where n is the normal at the curren
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In summary, our implementation prov
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Chapter 8 Conclusion We have studie
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inks are beginning to find their wa
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Appendix A Derivation of K-M theory
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∆i − =(K + S) idx 202 ∆j −
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Equation A.8 is now: Rearranging yi
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and if the paint is infinitely thic
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One concatenates the layers into a
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210 Figure B.1: Cold Glauconite in
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Table B.1: Color conversions from t
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214 Figure B.4: Munsell plots of Co
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216 Figure B.5: Burnt Sienna in dif
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220 Figure B.8: Munsell plots of La
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222 Figure B.9: Red Ochre Tint in d
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226 Figure B.12: Munsell plots of C
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228 Figure B.13: Variation of spect
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230 Figure B.15: Variation of spect
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Table B.13: Color conversions of Bu
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234 Figure B.18: Munsell plots of C
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236 Figure B.20: Munsell plots of R
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References [Alb71] Josef Albers. In
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240 [GLL + 04] Michael Goesele, Hen
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242 [KM31] Paul Kubelka and Franz M
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[Rat72] Floyd Ratliff. Contour and
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