Patricia A. Morrison
Give a brief lecture on electromagnetic energy. Light is only a tiny fraction of the electromagnetic spectrum, but since we have built in receptors for this part, it fascinates us. Color makes
The Blacksmith's Shop
far more dramatic than a black and white reproduction. The color of light depends simply on the predominant wavelength; the far more complicated color of an object depends on the light it reflects. When all colors of light are combined one gets white. When all colors of pigments are combined, one gets black; there is nothing left to reflect. Tomorrow we will do two simple experiments to illustrate this point.
Assignment: Read Physical Science text pp. 535-543.
Lesson Fourteen Lab: Radial Chromatography and Light through a Prism
To illustrate that white light and black pigment are both combinations of all colors, we will separate out the colors of both. Students can separate white light by passing normal light from the sun or electric classroom lighting through a prism while waiting for their chromatogram to develop. (We will use a variety of chandelier prisms.) Using chromatography we will separate black pigments. To make a radial chromatogram students will draw a quarter-sized circle in the center of a 5"diameter circular piece of filter paper with a small hole in the center. On the circle they will place six equally spaced dots from six different pens. The various brand pens all contain water-soluble black ink. They will then make a filter paper cone wick, using a third of a piece of filter paper, to set in a plastic cup with one half inch of water. The point of the wick rests in the hole of the filter paper, which is supported by the cup rim. Wait for the chromatogram to develop.
Assignment: Complete lab report according to standard format:
Purpose:
Equipment and supplies:
Method:
Data and observations: (A chromatogram is data and must be included in report. Write out observations carefully.)
Conclusion: (Must relate to purpose.) Explain (hypothesize) why your chromatogram looks like it does.
Lesson Fifteen Discuss lab. Chromatography is a race. At the beginning all components of the mixture are combined in a "stationary" phase (on the filter paper), but as time passes, those substances that have a greater affinity for the mobile phase (the solvent that passes through or over the initial phase) outdistance those substances which prefer the stationary phase. "Eventually all molecules will be separated into homogeneous groups (zones or bands)." (GHAMIS, Publication distributed at April 28th Workshop at SHU)
For further exploration there are two take-home challenges: "Chromatography on Paper," chromatograms of various colored markers using various solvents, and "Fabric Chromatography," emphasizing the difference between "bleeding" and chromatography. Other aspects of chromatography to research include: thin layer chromatography, high pressure liquid chromatography, gas chromatography, and forensic applications of chromatography. (SHU, April 28th Workshop)
Return to painting and introduce color theory with chart on board listing the six primary and secondary colors: magenta, red, yellow, green, cyan blue and dark blue. Emphasize that with the primary colors of pigments magenta, yellow and cyan blue one can make all colors in nature. These primary pigment colors are the secondary colors of light. With the primary colors needed to produce white light red, green and yellow one can make all the colors that one sees on the television screen. (Parramon, 12)
Using light filters from the theater department demonstrate combining primary light colors to get secondary light colors. Emphasize that combining light is an additive process, whereas combining pigments is a subtractive process. Any color that one sees is due to the light waves that remain after others are absorbed or transmitted. When one mixes two pigments, the number of light waves absorbed increases, while the number reflected decreases, making combining pigments a subtractive process. Mixing two pigments always decreases brightness. (Parramon, 14-16; Williams, Trinklein, & Metcalfe, 328-333)
(figure available in print form)
Explain that one can easily speak about light in terms of wavelengths, frequency, or energy, but color is a much more complicated topic to discuss. The transition from one color to the next is very gradual; the colors "merge." The difference between light of one wavelength and light at the next unit wavelength verges on the imperceptible. (Turner, 76) A combination of physical, chemical, physiological and psychological processes determine color vision. (Zollinger, 9) All people do not perceive colors identically; for instance people see colors such as gray, brown, and purple which are not even part of the spectrum. (Turner, 78)
Assignment: Activity: "Identification of Headache Remedies" based on chromatograms. (Handout, SHU April 28th Workshop.
Chemicals in Action
Ch. 3 "Separation of Matter" p.60)
Lesson Sixteen (two to three days) Interdisciplinary Activity with Visual Art's Teacher
Objective: To explore color theory of paints and pigments
Materials: Rice paper (very absorbent), primary colored drawing inks, pens, variety of
chemical glassware, flowers
Method: Teach students two basic Japanese brush strokes one creates bamboo; the
second creates flower petals or wings
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Teach students how to load brush (creates different values)
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Teach students about mixing pigment colors
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Mix primaries to get secondary colors
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Mix complements to gray down colors (changes saturation)
Using above techniques each student paints a picture combining chemical
glassware and flowers.
"Data": Terms and concepts students should fully understand: color wheel; primary,
secondary, intermediate, and complementary colors; hue (color), value
(lightness or darkness tint or shade), and saturation or intensity
(brightness or dullness)
Conclusion: Each student produces a painting and writes a paragraph explaining how his or her picture illustrates the above terms. Using a criterion sheet distributed at the beginning of the project students evaluate their own work before the teachers grade the activity. Attitude, careful use of materials, following directions, and wise use of time account for the 50% of grade determined by art teacher; writing accurate, complete definitions of terms and a clear insightful paragraph about their painting account for the 50% of grade given by chemistry teacher. Together with the art teacher we will again observe The Blacksmith's Shop to review hue, value, and saturation and note Wright's use of color.
Assignment: First Day Read The Visual Experience, "Color" pp.62-66
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Second Day Complete write-up and evaluation for interdisciplinary project
After working with pigments to create an original painting and seeing how pigments interact with each other we find that several questions posed earlier again arise. What causes the color of a pigment? Why do pigments absorb particular rays and reflect others? The answers to these questions must be postponed until we've studied atomic structure. As the year progresses I will again return to the painting while teaching the following units:
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1. Bright line emission spectrum, atomic structure, energy levels and electron
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Configuration return to light and color
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2. Creation of elements interplay of religion and technology in painting
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3. Ionic compounds, crystalline structure and transition metals exploration of most commonly used oil pigments and specific factors that cause colors. We will consider what pigments Wright might have used and which ones were not available to him. What do contemporary art students use in place of lead carbonate, an essential white pigment for Wright?
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4. Organic chemistry interdisciplinary activity with visual arts teacher focused on art materials which exist as a result of chemistry. This activity emphasizes the influence of chemistry on art mediums and, therefore, artists. Before the advent of commercial pigments artists were more attuned to the chemistry of the materials they used; synthetic materials were unknown
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5. Final visit to the Yale University Art Gallery Conservation Laboratory in the spring. By this time students should understand the basic principles behind the scientific equipment used and have some appreciation for the chemistry involved in preserving and restoring works of art. This visit will summarize and complete the idea that science and art are intimately related.