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

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2.3.4 Waxes Historically, the most important wax for artistic purposes is beeswax. Chemically, beeswax contains some free fatty acids, hydrocarbons, and esters formed from alcohols and fatty acids. Similar to drying oils, beeswax can be dissolved in natural solvents. Encaustic, or the method of painting with wax, originates from ancient Greece. Heat is used to liquefy the media, and the paint is applied hot with a brush or palette knife (encaustic literally means “burned in”). Hence, the wax does not dry, yet congeals as it cools. In modern usage, the beeswax is often combined with resin or turpentine to increase the fluidity of the paint. A wide range of textures is possible by varying the consistency of the paint. Applying external heat to the artwork makes some additional effects. An artist may heat behind the support to keep the surface warm while brush marks are made or apply heat to the paint surface to burn in (fuse and adhere) existing layers. Encaustic paintings have a unique lustrous, rich, and translucent surface. Due to the cumbersome nature of its equipment, it was displaced by other media (tempera and oil) in the Medieval and Renaissance periods. However, encaustic has seen resurgence in modern times due to the abundance of tools to manipulate the media, including hot plates, electric tools and heat lamps. Also, since wax readily dissolves in turpentine, it is sometimes used as an additive in oil paint for its textural and optical properties. 2.3.5 Synthetic Polymers Rivaling oil in its versatility is a modern paint formulated from a synthetic polymer referred to as acrylic polymer emulsion, or commonly known as simply acrylic. 43
While it has been used since the 1930s, widespread use followed commercial man- ufacture in the 1950s. Artists are drawn to its quick-drying behavior (a matter of minutes) and tough, flexible film suitable for almost any surface. Also, the media uses water as a vehicle, eliminating the toxic fumes from oil’s solvents in the studio. This simplifies cleanup of brushes and thinning of the paint as well. One of the most compelling qualities of acrylic paint is its uncanny resemblance to almost any other media, via manipulating the substance with various additives. It can be thinned and used in light washes on paper as in watercolor, or thickened and applied to large panels of canvas as in oil. It does not require the same support preparation as other media and can be applied to unprimed surfaces, as it is resistant to moisture upon drying. Similar to oil, additives can alter the finish, viscosity, texture, and drying properties of acrylic paint. However, there are drawbacks to this new medium. The acrylic polymer emulsion used as a binder is not as transparent as some other painting media, resulting in a slightly less luminous surface. Another disadvantage is that acrylic cannot hold as much pigment as other binders, which results in a slight hue reduction. In regards to art conservation, not enough research has been done to examine the longevity of acrylic polymer emulsion as a suitable binder, in comparison to historical binders. 2.3.6 Catalytic Materials There exists another form of painting that does not conform to our usual definition of paint. In this case, the pigment is spread onto the surface of a wall without the presence of a binder. The adhesion of particles to the support is the result of a chemical process between the plaster of the wall and the air. Hence, the 44
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PIGMENTED COLORANTS: DEPENDENCE ON
Page 3 and 4:
ABSTRACT We present a physically ba
Page 5 and 6: Acknowledgements This work would no
Page 7 and 8: Table of Contents 1 Introduction 1
Page 9 and 10: List of Tables 2.1 Average pigment
Page 11 and 12: 3.15 Photoreceptor absorption .....
Page 13 and 14: B.15 Variation of spectral reflecta
Page 15 and 16: corrode the surfaces of materials.
Page 17 and 18: Figure 1.1: Detail of the Azor-Sado
Page 19 and 20: However, since mural artwork is typ
Page 21 and 22: at a very high quality (albeit limi
Page 23 and 24: heterogeneous sum of very different
Page 25 and 26: which linseed oil derives (the most
Page 27 and 28: oration of a rigidly painted layer
Page 29 and 30: ing will hit the ground and reflect
Page 31 and 32: tion of paint tubes in 1841 and the
Page 33 and 34: Figure 2.8: Natural pigments of ant
Page 35 and 36: ecome more common recently. The Ame
Page 37 and 38: A V = O(r2 ) O(r3 ) = 1 O(r) 24 (2.
Page 39 and 40: Table 2.2: Pigment specific gravity
Page 41 and 42: provide the underlying color to a p
Page 43 and 44: though the speed of light in air is
Page 45 and 46: In general, when light travels from
Page 47 and 48: materials while lit from behind. Li
Page 49 and 50: Table 2.4: Index of refraction η f
Page 51 and 52: to completely congeal. Hence, these
Page 53 and 54: ond together to form proteins. Exam
Page 55: to its original state by any means.
Page 59 and 60: organic binder found in more conven
Page 61 and 62: 3.1.1 Visible Light Spectrum Light
Page 63 and 64: Figure 3.2: Hue, brightness and sat
Page 65 and 66: measures how much light is reflecte
Page 67 and 68: Figure 3.6: Additive color mixing o
Page 69 and 70: Figure 3.9: The physical amount of
Page 71 and 72: The vascular tunic lies on the wall
Page 73 and 74: Figure 3.11: Cross section of the r
Page 75 and 76: Not all areas have the same sensiti
Page 77 and 78: identify and distinguish between va
Page 79 and 80: that range between zero and full in
Page 81 and 82: spectrum. This insures that the res
Page 83 and 84: Figure 3.19: Graphical representati
Page 85 and 86: X x = (X + Y + Z) Y y = (X + Y + Z)
Page 87 and 88: color into the appropriate RGB colo
Page 89 and 90: components in the image (the smalle
Page 91 and 92: haviors of subtractive mixing and i
Page 93 and 94: of perceptually equal sizes. Unfort
Page 95 and 96: enabling one to transform between t
Page 97 and 98: andwidth as converted signals are s
Page 99 and 100: Figure 3.28: Retinal ganglion recep
Page 101 and 102: 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
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Chapter 4 Previous Work There is no
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different location. Subsurface scat
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describes the scattering and absorp
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only accounts for a small percentag
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σ ′ t = σa + σ ′ s and α
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104 Figure 4.4: A model of an alaba
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effects or are too computationally
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108 Figure 4.6: Results using Kubel
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specifying pigments works adequatel
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color representation, it is not fea
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time. A metallic surface patina is
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the system consisted of wetness and
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or darkening enables the museum per
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in front of a displayed work. Felle
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light exposure. This effect is espe
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over time. Perceptually, these hues
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The rate of change of the concentra
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over white grounds) suffer the grea
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protects the deeper remaining color
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light source. This method is used w
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chemical smog and have been identif
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Chapter 5 Preparation & Measurement
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tending transparent pigments used i
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140 Figure 5.1: Spectral reflectanc
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the requirements of the work at han
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144 Figure 5.2: Left: Magnified vie
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Table 5.2: Relevant data regarding
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historically one of the best grades
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created far too strong of a binder,
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too brittle and cracking. While wor
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154 Figure 5.4: Reflectance values
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5.1.5 Painting After the layers of
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The gray card reflected 18% of the
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160 Figure 5.8: The optical setup f
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Note that harmonics reflect at the
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Note that the calibration factors f
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Chapter 6 Experimental Results 6.1
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168 Figure 6.1: Lapis Lazuli in dif
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(such as CIE standards C, D50, orD6
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172 Table 6.2: Perceptual differenc
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174 Figure 6.3: Munsell plots of La
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and j has a saturation of red rsat,
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178 Figure 6.4: Variation of spectr
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visible spectrum are increasing at
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182 Figure 6.5: Munsell plots of La
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trying to match color ca from the p
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as it ages. This is in direct contr
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teractive viewer. In our applicatio
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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
Page 237 and 238:
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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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