Afterimages

If one's attention is focused on an area of a single color for thirty to sixty seconds and then shifted to a field of white (Figure 4.3), the eye will sense a color other than the first one covering the white field. The second color is complementary to the first color. For example, red will produce an afterimage of green, and blue will produce an orange afterimage. The complementary afterimage appears as a luminous transparency. The effect is similar to that obtained by viewing the white...

Bi Index of Refraction

Refraction refers to the change in direction of light resulting from the change in the velocity as light passes from one medium into another. 'Information is also available on the Internet in Patterns in Nature under Readings on Reflection and Refraction. http acept.la.asu.edu PiN Fig. B.1. Schematic illustration of a wave front of a light wave in air incident on a transparent medium (here, glass) that has a greater density (higher refractive index) than that of air. The wave moves more slowly...

Ci Mechanism for the Absorption of Light

Electron Binding Energy

The formula for the absorption of light in the simplest case starts with a beam of light of intensity (or flux of photons) I that has just penetrated Fig. C.1. Schematic of light rays penetrating to different depths into a paint film with photon-absorbing pigment particles. Fig. C.1. Schematic of light rays penetrating to different depths into a paint film with photon-absorbing pigment particles. into a material with a uniform concentration of absorbing pigments. We ignore reflection and...

E Xray Crystallography

The atomic structure of a crystal is deduced from the way it diffracts a beam of x-rays in different directions. A crystal is built of countless small structural units, each consisting of the same arrangement of atoms the units are repeated regularly like a wallpaper pattern, except that in a crystal the pattern extends in three dimensions in space. The directions of the diffracted beams depend on the repeat distances of the pattern. The strengths of the diffracted beams, on the other hand,...

Proton Induced Xray Emission

In the preceding sections we have discussed the formation of electron vacancies in inner shells (n 1, 2, ) by incident x-rays. Characteris- X-Ray Energies in keV for Characteristic X-rays* Emitted from Elements in Common Pigments *In x-ray notation, the capital letter (K, L, M, ) indicates the shell containing the vacancy. The subscript a indicates the most intense line. The electron transitions are Ka (l3 to k), Kp (m5 to k), La (m5 to l3), Ma (n7 to m5). *In x-ray notation, the capital letter...

Photon Absorption Visible Infrared and Xrays

The observation of the visible colors of a painting and the analysis of a painting by low-energy infrared (IR) and by high-energy x-ray photons all depend on the absorption of photons by the materials in the painting. The absorption mechanism is the same for all three regions of the electromagnetic spectrum, but the effects differ. In the visible region, absorption of selected wavelengths leads to the appearance of color, because the absorbed wavelengths are absent in reflected light. In the...

And the Photoelectric

The focus in this book is on the interaction of electromagnetic waves with electrons contained in the pigments, binders, and support that comprise a work of art.1 These waves have wavelengths that range from 1 nanometer (10 9 meter) for x-rays to 1 kilometer (103 meters) for radio waves. Wavelengths of visible light are in the range of 400 to 700 nanometers (nm). In this appendix we consider the formulation of photon wavelength and energy as well as the absorption of a photon by an electron....

Carbohydrate Containing Binders

Carbohydrates are compounds that contain carbon, hydrogen, and oxygen. The basic building blocks of carbohydrates are simple sugars, or (in the nomenclature of organic chemistry) monosaccharides. Some simple sugars contain five carbon atoms, others six. The six-carbon simple sugar known as glucose is probably the most abundant organic compound on the earth. Another common simple sugar is fructose, which is found in honey and many fruit juices. Simple sugars can be bonded together to form larger...

Protein Containing Materials

Illumination Art Lesson

Garden Scene, late 15th century Persia Timuria period. Ink and colors on paper. Although the binder used in this painting is not known, it could well have been a natural plant gum, which documentary sources indicate was a common binder for such paintings. Most of the paint here was applied in fairly thick opaque layers, although thinner wash-like layers were used in places. Francis Bartlett Donation of 1912 and Picture Fund. (Courtesy, Museum of Fine Arts, Boston)...

Light Photons and Waves

The starting point for a description of color is a description of light. For that, we start with a beam of white light (Color Plate 19). When the beam of white light passes through a prism, the white light is split into many colors. As will be decribed later in detail, the beam of white light contains spectral color signals from red through violet. The prism separates the signals into the individual components. Isaac Newton demonstrated in 1672 that light could be split into many colors by a...

Absorption of Light

As we pointed out in Chapter 5, the mechanism for the production of color by materials is the selective removal of certain wavelengths (or energies) of light from the electromagnetic spectrum. The light penetrates into the material and encounters light-absorbing pigment particles for this selective removal to occur. A photon transfers all of its energy to the absorbing pigment and is lost, absorbed, that is, from the light beam. The nonabsorbed photons are scattered (or reflected) back from the...

L Dendrochronology Treering Dating of Panel Paintings

L-1 Baillie, M.G.L., Tree-Ring Dating and Archaeology, London Croom, Helm L-2 Baillie, M.G.L., Is There a Single British Isles Oak Tree-Ring Signal The Proceedings of the 22nd Symposium on Archaeometry Held at the University of Bradford, Bradford, U.K. 30th March-3rd April 1982 1983 73-82. L-3 Bauch, J., and Eckstein, D., Dendrochronological Dating of Oak Panels of Dutch Seventeenth-Century Paintings, Studies in Conservation 15 1970 45-50. L-4 Bauch, J., and Eckstein, D., Woodbiological...

Radiocarbon Dating

Radiocarbon Upper Atmosphere Image

The impact of high-energy primary and secondary cosmic rays on atoms and molecules of the upper layers of the earth's atmosphere lower stratosphere and upper troposphere results in many nuclear reactions in which a number of neutrons, protons, a-particles and other subatomic particles are produced Figure K.1 . A large portion of neutrons produced by cosmic rays are slowed down by collision with atoms in the atmosphere. The resulting thermal neutrons react with 14N atoms to form a 14C atom and a...

F Xray Emission

Images Shell Emission

Bohr proposed that an atom can absorb radiation only at a frequency f that corresponds to the difference in energy AE between two allowed quantum states This is illustrated in Figure F.5. An electron cannot jump from a lower to a higher energy state unless this exact amount of energy is supplied to it. Conversely, when an atom in a higher state falls to a lower state, the frequency of radiation given off is dictated by the relationship just given. For x-ray emission, when an electron is ejected...

Polarized Light and Optical Microscopy

Polarized Optical Microscopy

Light of a single color can be described as a wave with a specified wavelength or as a stream of photons with a specified energy. Another aspect of light is that it can be polarized with the wave vibrations lying in one plane. Many pigment crystallites respond differently in their ability to transmit light depending on the relation of the plane of polarization to the crystal axes of the pigment. In optical microscopy, the light beams can be polarized by use of filters. Pigments can be...

Introduction

Black Bison Cave Painting

Paints almost always consist of pigments, which provide the color, and an adhesive material that binds the pigment particles together and joins them to the substrate to which they are applied. Rarely, one material could serve as both pigment and binder. For example, Paleolithic cave paintings Figure 3.1 at least in some cases were probably done with clay-containing earth pigments the clay component, when moistened, would have given the earth pigments enough stickiness to adhere to the cave...

Refraction

Stirring Rod Refraction

Optical properties of materials are characterized in part by their refraction of light. Light incident at the interface between two materials has a transmitted component whose direction changes as it passes the interface. For example, rays of light change direction, or are refracted, when passing from air into glass. As shown in Figure 6.5, one component of light is reflected, while the other component is refracted. The refracted beam changes direction at the interface and deviates from a...

E Structure of Pigment Crystallites

Perpendicular Axes

The regularity of the external form of crystals suggests that crystals are formed by the regular repetition of identical building blocks Figure E.4 . When a crystal grows in a constant environment, the shape remains unchanged during growth, as if identical building blocks were being added continuously. The building blocks are atoms or groups of atoms A crystal is a three-dimensional periodic array of atoms. This was learned in the eighteenth century when mineralogists discovered that the index...

Relations Between Measured and Calendar

14c Clibration Curve

The basic assumptions of radiocarbon dating are a constant rate of radioactive decay uninfluenced by external factors and constant concentration of 14C in the biosphere. The first assumption has been found correct. The second assumption has been found only approximately correct. The rate of 14C production depends on the stability of cosmic-ray flux. Dendrochronology tree ring dating method together with high precision 14C dating allowed for measurement of variation in 14C production back to...

B Reflection and Scattering

When light is incident on a transparent material such as glass, the light is reflected from the surface as well as refracted as it passes into the material. As shown in Figure B.4, the angle of incidence i is equal to the angle of reflection i' angle of incidence i angle of reflection i' B.4 Fig. B.4. The paths of rays of light incident on a glass plate at angle of incidence i and then about 4 reflected at the air glass interface and the remainder refracted at an angle r. As the light ray exits...

B Hiding Power

Light Refraction Varnish Paintings

Hiding power is the measure of a paint's ability to cover a surface opaquely so that an underlying paint cannot be seen in visible light. Absorption is one factor in the hiding power of a paint. Darker colors absorb more intensely than lighter colors and hence have a greater hiding power. The refractive index can play a major role in determining hiding power. The amount of light scattered or reflected from the interface of a composite of two materials depends strongly upon the difference...

Pigment Response to Xrays Emission

Particle Induced Ray Emission Pixe

Pigments have been characterized by their color and their relative transparency to infrared and x-radiation. The induced emission of x-rays also provides a means for pigment identification. An incident x-ray photon is absorbed and an electron is ejected from the atom, leaving an unfilled state. There is a specific set of energy states occupied by the electrons. No two electrons can occupy the same state. An electron in the atom makes a transition to fill the empty state, and an x-ray is...

Infrared Reflectography and Hiding Thickness

Infrared Reflectography

When it comes to the study of under-sketching rather than underpainting, scientific emphasis switches to infrared reflectography. X-rays are scarcely able to make any distinction between a plain chalk ground Fig. C.6 and one only slightly altered by addition of a thin sketch line in charcoal and bone black. But infrared radiation of wavelengths around 2.0 microns, having penetrated the upper paint layers, in particular the pigment, will be reflected at the level of the sketch and by virtue of...

Pigment Response to Neutrons

Drawing Analysis Shape

A beam of neutrons incident on a painting will induce reactions within the elements present in the pigments. These reactions lead to the emission of beta rays and gamma rays. As is the case in x-ray emission, the energies of the emitted gamma rays identify the elements. Beta-ray emission allows one to examine the distribution of elements across a painting in a manner similar to x-radiography. An autoradiograph of Anthony Van Dyck's Saint Rosalie Interceding for the Plague-Stricken of Palermo...

Accelerator Mass Spectrometer

Tandem Accelerator

A new era of application of radiocarbon dating came with development of the alternative method of 14C detection based on direct analytical determination of the concentration ratio of 14C and stable carbon isotopes in the analyzed sample K7 . The conventional 14C counting methods provide information about concentration of 14C in the sample based on radioactive decay and measurement of beta particles emitted from the sample. A more efficient method for 14C measurement would be a direct analytical...

Dating and Pigment Identification

Painting Autoradiography Reactor

At this point we go beyond routine visual examination procedures and attempt to date the painting. The suspect work of art can be dated by dendochronology Appendix L if a wooden panel support is used or by carbon-14 techniques Appendix K if a canvas is used as support. One can also reach conclusions about a painting's date by determining the elemental composition of inorganic pigments. Element identification can be made by x-ray fluorescence, XRF Appendix F , or by particle-induced x-ray...

Fresco

Seams Between Giornate

Fresco is an ancient technique of painting on masonry walls. The color in Diego Rivera's murals at the Detroit Institute of Arts Color Plate 6 was applied to damp plaster hence the term fresco, or fresh in Italian . The material used to paint frescos does not conform to our usual definition of a paint, which specifies the presence of a binder. The pigment is ground in water, which has no binding strength. Water is a vehicle, or diluent, which evaporates during the drying process. The water is...

Pigment

Fresco Intonacco

A leading manufacturer of artist's paint currently lists at least 108 different colors of oil paint. The pigments selected for these colors are uniform in particle size, compatible with oil binders, are reasonably resistant to atmospheric gases and light, and are for the most part permanent. These modern pigments are also relatively uniform in consistency, workability, and drying time from color to color. Even though some of the 108 colors are mixes of two or more pigments a flesh color might...

The Chromaticity Diagram

Cie Chromaticity Diagram

The sensation of color depends primarily on the composition of light, which is a mixture of white light and colored light which in itself can be a mixture of wavelengths as in the case of purple . The colored light may have a dominant wavelength, or hue, and the extent to which the hue dominates is known as saturation or chroma . The saturation decreases as the hue is diluted with white light. There are three types of receptors in the eye that respond to different wavelengths Chapter 4 . This...

Successful Forger

Lead Tin Yellow Pigment

It is difficult to be a successful forger. Not only must the forger possess impressive artistic skills, he must have a general knowledge of a particular historical period as well as an understanding of the materials and methods employed by artists of the period. One starts with the support for European paintings the choices are wooden panels or canvas, depending on artist, time period, and geographic location. Both types of support can be easily dated, so the supports must be obtained from a...

H Fourier Transform Infrared Spectrometry

Ftir Lead White

The infrared region of the electromagnetic spectrum is the region on the longer-wavelength side of the visible spectrum. Infrared radiation can not be seen by our eyes, but we sense it as heat all hot objects give off considerable infrared radiation . Infrared reflectography described earlier in this book, uses near infrared radiation, that is, infrared radiation just beyond the red part of the visible light spectrum. The infrared radiation used in IR reflectography goes out to wavelengths of...

Pigment Response in the Infrared

Dona Isabel

In the infrared portion of the spectrum the wavelengths are greater than 700 nanometers with photon energies less than 1.8 electron volts 76 eV . These infrared photon energies, typically around 1 eV, are so low that the photons are not absorbed by most pigments. The paint layers are therefore relatively transparent to infrared radiation. Infrared radiation penetrates the upper paint layers but is absorbed by dark preliminary drawings that reside beneath them. The remaining radiation is...

B Dispersion

Dispersion Curve Prism

The index of refraction or decrease in velocity depends on wavelength, with the velocity decrease more pronounced for blue light than for red. Thus, when parallel beams of red and blue light enter glass, the blue light is bent more at the air glass interface than the red light Figure B.6 . This spreading of the beam is called dispersion. The dispersion curve in the visible region of crown glass is shown in Figure B.7. Although the difference in refractive index between that for blue, n 1.51,...

Beyond Analysis

Girl Asleep Vermeer Xray

The analysis of paintings provides extremely valuable information to those concerned with the conservation, authenticity, and art-historical aspects of these very complex art objects. Analysis also establishes for the practicing artist a body of practical knowledge concerning historical methods and materials. We have made the general argument that the information obtained through scientific methods of analysis in conjunction with an understanding of how paintings interact with the forces of...

ENeutron Activation and Autoradiography

Ainsworth et al., Art and Autoradiography The Metropolitan Museum of Art, New York, 1982 . E-2 W.J. Young, Ed. , A.A. Gordus, Neutron Activation Analysis of Streaks from Coins and Metallic Works of Art in Application of Science in Examination of Works of Art Museum of Fine Arts, Boston, 1973 . E-3 B. Keisch, Secrets of the Past Nuclear Energy Applications in Art and Archaeology US AEC, 1972. E-4 E.V. Sayre et al., Eds. P. Meyers, The Structure of Works of Art and Historic Artifacts, in...

Cross Section Analysis of Sample from Detroit Industry by Diego Rivera

STODULSKI, Detroit Institute of Arts JERRY JOURDAN, BASF, Inc. Buon fresco technique requires applying very finely ground natural and synthetic alkali stable pigments suspended in water onto wet plaster. As the plaster sets by chemical reaction with atmospheric carbon dioxide, the pigments become an integral part of the wall surface. This produces a very tough, colored surface. The extent to which this technique produces pigment embedded in the wall's surface and not...

H Chromatography

Paint Analysis

Chromatography is the name for a group of analytical procedures widely used in the identification of many organic materials. The name for the general procedure came from its first application in 1906, when an extract from leaves was flushed through a column packed with calcium carbonate. The extract separated into a number of differently colored bands as it passed through the column. Each band essentially represented a different compound contained in the extract. All chromatographic techniques...

Examination and Analysis

We have described a painting as an object made from a variety of materials carefully chosen by the painter. But how is it constructed, what are its materials, and how is our visual response generated by the result of their combination A series of analytical techniques has been developed to help answer these questions. The techniques employed in the scientific analysis of paintings follow a sequence beginning with an external view with the unaided eye. Much information is available from this...

Gi Nuclear Reactions

In this section we present the basic terminology and concepts involved in nuclear reactions. We are primarily concerned with two reactions 1 The nucleus can be excited to a higher energy state analogous to promoting an electron to a higher energy state in atomic spectroscopy the nucleus can then de-excite by y-ray emission 7 is the Greek letter gamma 2 A different nucleus Y may be formed as a result of the nuclear reaction between an incident proton or neutron and the target nucleus X. In most...

Simultaneous Contrast

Included in Aristotle's book On Sense and the Sensible is a description of the three primary ways of mixing colors. One approach is to mix a quantity of one color of paint with a quantity of another color, producing a third, distinctive color of paint, ready to be applied to the painting surface. A second is to place a transparency of one color over an area of another color. In most cases, the transparency is accomplished by adding binder or diluent to the paint to disperse the particles of...

C Scientific Analysis

Bragg, X-ray Crystallography Scientific American, July 1988. C-2 B.D. Cullity, Elements of X-ray Diffraction Addison-Wesley, Reading, Mass., 1978 2nd Edition. C-3 R.E. Dickerson and I.Geis, Chemistry, Matter and the Universe, W.A. Benjamin, Menlo Park, CA., 1976 . C-4 L.C. Feldman and J.W. Mayer, Fundamentals of Surface and Thin Film Analysis, North-Holland, New York, 1986 . C-5 S.J. Fleming, An Evaluation of Physics-Chemical Approaches to Authentication in Authentication in the Visual...

Dendrochronology Tree Ring Dating of Panel Paintings

Dendrochronology Painting

Contributed by PETER IAN KUNIHOLM The Malcolm and Carolyn Wiener Laboratory for Aegean and Near Eastern Dendrochronology Department of the History of Art and Archaeology Cornell University Many European paintings are painted on solid wooden panels or boards, typically oak for Netherlandish paintings. The wood is usually split radially so that, in ideal circumstances, a sequence of annual growth rings from pith to sapwood is present. These sequences are then matched, one against another, by the...

Color Light and Space

In the world around us, color appears to be attached to everything we see. It changes as the light changes, but usually within predictable limits, or at least we recognize that a color linked to an object appears a certain way in a certain kind of light. We are conditioned enough by this that we often identify an object by its color. And we are conditioned enough by the change of light to recognize the same object by color even though the condition of light has changed the color of the object....

Pigment Response to Xrays Absorption

Young Girl Reading Ray

In the x-ray portion of the electromagnetic spectrum the wavelengths are around 1 nanometer, a distance nearly one thousand times smaller than wavelengths in the visible spectrum. Consequently, the photon energies are a thousand times greater than the energies of photons in the visible region. In the x-ray region, photon energies are typically in the range of 1,000 to 20,000 electron volts 1 to 20 kiloelectron volts, or keV with an upper level in the range of 100 keV. Above that level, photons...

Neutron Activation Analysis and Autoradiography

Neutron Activatione Analysis

Almost all of neutron activation analysis depends on the relatively high probability that a slow-moving neutron can be captured by an atomic nucleus. This reaction forms a new isotope with a mass number one unit larger than the target atom In this reaction the atomic number Z of the nucleus is unchanged. When the atoms of an element are bombarded by neutrons in a reactor, some of them will absorb a neutron and become radioactive. For example, in the case of sodium, A sodium nucleus with 12...

N Organic Binders Analytical Procedures

Infrared Microspectroscopy in the Analysis of Cultural Artifacts, Practical Guide to Infrared Microspectroscopy. New York Marcel Dekker, 1995, 287-322. N-2 S. Halpine. A New Amino Acid Analysis System for Characterizing Small Paint Samples Identification of Egg Tempera and Distemper in a Painting by Cosimo Tura. Studies in Conservation 37 1992 , 22-38. N-3 S. Halpine. An Investigation of Artists' Materials Using Amino Acid Analysis Introduction of the One-Hour...

Paint

Grinding Pigment

The paint used by artists to project their ideas and observations can be as simple as a mixture of pigment and binder, with pigment providing the color and the binder joining the particles of pigment together and to the support. A paint may also contain a vehicle that dilutes the pigment binder mixture, allowing the paint to be spread more easily. Other materials may be added to the mixture to enhance the optical or textural characteristics, or to alter the working properties, by accelerating...

Natural Resins

Natural resins are sticky, water-insoluble substances that exude from a wide variety of trees. Most consist of compounds known as terpenoids. The resin that exudes from some types of trees contains copious amounts of natural solvents. One example is pine resin, from which turpentine, a natural solvent is distilled. Resins were known in ancient Egypt, and quite probably earlier. In Egyptian times, they were used in varnishes and figured in mummification procedures, among other uses. A...