Allen A. Denio University of Wisconsin I Chemistry

Eau Claire 54701 I Academic chemistry departments devote most of their

educational efforts to students enrolled in chemistry or chemical engineering, the health professions, and a variety of fields that deem it essential that a year or two of chemistry is "good for the soul" if not actually useful in the profession. A small but rather important effort is focused tm the nonscience maiors. A varietv of introductorv courses are offered to permit nonscience majors to meet the degree science requirements.

Most of these introductorv terminal courses tend to be quite general in their scopes and frequently concentrate on relevant topics such as environmental problems, food additives, the "pill," and corrosion. The number of texts available for these courses has grown suhstantiallv and the quality of some is quite impressive. The present enthusiasm displayed hy many chemistrv faculties in this area is encouraging since the stu- dents mrolled rttpresent an impnrtnnt segment uf the furwe el~rrorsand in twtain caaes rlwted ~~flia.ials. It is interesting to sp~:culitte how our national science policy (or lark of same) might ditt'er if the mrmhers of Congress had taken a h s i c t~h~mis t rv course f r m a aiflcd eduwtor sut h as Jorl Hilde- brand, Harvey Sorum, or Huhert Alyea.

Providing a single course for the nonscience majors a t a university is indeed economical and efficient. Under present funding levels faculty creativity can he greatly curtailed! Recall the wise words of George Hammond: "The thing that bothers me most is that there is so little variety in chemical education. I t is a pity that students are all learning the same things, because there's an awful lot of chemistry that none of them is learning." (I ).

An important group of students that generally avoid chemistry courses a t a university are those from the Art De- partment. Most of these highly talented students satisfy their science requirements in other departments such as Biology (Sex and Nutrition-two separate courses!), Physics (As- tronomv and the Mvsterious Universe), and Geology (Rocks and Minerals). Yet it seems to the author that the& is much chemistry that should he of interest to art students. Paint

and solvents, clays and ceramic glazes, dyes and fi- bers, metals, glass and plastics are materials used by artists in their endeavors. The literature included a report on an in- terdisciplinary course between chemistry and art, designed for an interim session or minisemester (2). More recently, a semester length course entitled "The Molecular Basis of Form and Color: A Chemistry Course for Art Majors" was discussed (3). An excellent feature of this offering is the emphasis on the chemistrv and nhvsics of color with respect to art media.

"~he&ry ;or ~ r t i s t s and Art ~uffs '" was developed with coo~eration from the Art Faculty and was established as a three (semester) credit course, having two lectures and a two-hour laboratory session each week. I t can he taken by art students or other nonscience majors as part of the degree science requirement. The course was first offered in 1974.

Goals

are often exposed in their work-and teach them .mf~ proce- dures.

for Artists and Art Buffs

4) To expose thestudentstn that part of the literature from which they can hen& in their work.

5) To lower the harriers tocommunication between chemistsand artists.

Instructional Strategy The approach must he "colorful" and nonmathematical.

Emphasis should be given to the use of models, visual aids, and lecture demonstrations. I t is best to assume no prior hack- ground in chemistry, the normal case.

Approximately the first half of the course is basic intro- ductory material. However, it is essential to maintain the in- terest of art students a t this stage. This can be done by a careful choice of examples, such as cadmium sulfide, a com- mon pigment, to illustrate a binary compound or turpentine as an examnle of an organic liauid. Redox chemistrv can he approached from the firing conditions in the potter's kiln.

The applications of chemistry to art complete the course. The potential here is great and will normally vary with the interests and hnckground of the faculty member. The chem- istry of clay and gLae formation seems exceptionally fertile to the author. Other essential areas include pigments and paints, dyes and fibers, metals, glasses and plastics.

The laboratory has great potential for learning in chemistry courses, and this presents a real challenge in the present case. The normal experiments for an introductory course do not generally apply, except for those used a t the beginning that deal with topics such as density or physical and chemical properties. One must build on the artist's interest in matter and how chemistry can modify color, shape, texture, and permanency.

Lecture Topics I. 11. 111. IV.

v. VI. VII.

VIlI

Types of matter. From what is matter made? The mysterious ntorns. Elements, the huilding hlocks of nature.

Chemical change and the hirth of a pigment. Chemical change and "fire." Chemical change as a way of life (and death).

Chemical bonds and "Elmem" atomic ghle

IX. What is color? X . Pigmentsrevisited. XI. Metals. XII. Ceramics.

XIII. Glass.

XIV. Paints. XV. Plastics. XVI. Fihers and dyes.

XVII Statunryrape

The first eight topics include the concepts of elements, atoms. chemical reactions and enerm changes, chemical bonds and compounds, nomenclature,~chemical formulas and equations, molecular shapes and sizes, simple weight rela- tionshins. reaction rates. and the Periodic Table.

A rajher descriptive approach is used. The atomic struc- tures of the first ten elements are discussed. each in relation to its position in the Periodic Table. T o illustrate, item I11 is presented with the subheadings used.

for the Art Department!

30 / Journal of Chemical Education

111. The Mysterious Atoms 1. Their bits and pieces.

2. The silent nucleus. 3:The electron cloud.

4. Isotopes, the pure "impurities."

5. Hydrogen, the simplest of all.

6. Helium, the balloonist's iov.

I . iithium, the lightest metal.

8. Beryllium, rare and deadly.

9. Boron, from gasoline to glass

10. Carbon, from charcoal to nylon.

11. Nitrogen, 8Wb of every breath. 12. Oxygen, 20% on which we

thrive. 15. Fluorine, from toothpaste to

Teflon. 14. Neon and the bright lihts.

15. Larger atoms to love and die for (or from).

16. Limits to growth.

17. Atomic dimensions, or think small.

Item IX (What is color?) includes the concept of electro- magnetic radiation, wavelength, frequency, and energy. The discussion proceeds to the interactions of light with matter and the resulting color perception.

Pigments are then studied in greater detail which includes an examination of the structure of more comnlex nizments . . , . and thts important physical properties.The toxiuty d 1 trtntn oirments is d~icllssed and the imls,rtance of stahilitv 111 heat. iiiht, and other compounds is kmphasized. The historical origins of pigments stimulate interest: it is imoressive that the ~ i i ~ t i a n s used a variety of pigments about 8000 B.C. The examination of pigments as a means of dating paintings has . . mndct lift! d~ffic~;lt tin forgers (1,.

The topiccd'm~.tals has nlmoit ~~ni\ ,ersal appeal to ari su1- rlmrs, he:inning with the precious mrtnli for th0.e interested in j t w r h ( le i i~n and fd~ricntion. Alloys such as hnrs.;, hn,n7e, Dewter and "Sterline" silver nrr diw~s.ied. alone with rlw , ~ ~ " ~ ~ ~~-~

troplating, galvanizing, and anodizing. The historical signif- icance of metals in artistic endeavors as well as commerce and warfare adds a hit of respect for early civilizations (5).

The chemistry of clay and ceramic glazes is interesting and makes the potter's work more meaningful. The chemicals used in a pottery studio are identical to many of those in a General Chemistry lab, except that they are sold in hulk quantities and in a finely powdered state, and lark the pedigree laheling . .. system used hy chemists.

The unique physical property of clays is the plasticity that results when the proper amonnt of water is added. This plasticity is accounted for by the very small particle size and the thin, wafer type crystals. Most particles are less than a micron in diameter, resulting in an enormous surface area per unit weight.

After a plasticized clay is "thrown" on a potter's wheel to form the desired ohject, it is air dried. The piece is then fired in a kiln a t temperatures up to about 1400°C. During the firing cycle a variety of changes occur. Initially the "free water" is removed, followed by the loss of the "chemically combined" water. Eventually the a-quartz form of silica that is stahle a t room temperature converts to 0-quartz a t about 537OC. This form changes to the cristohalite form of silica a t ahout 1200T. Kaolin is converted to metakaolin, then to spinel (MgAl,Oa), and finally to mullite.

"Kiln chemistrv" also includes the varietv of reactions of the clay impurities and the fuel comhu~t ion~roducts . Some of the gases evolved are hazardous and the need for proper . . ventilation is stressed.

The fired ceramic is porous and is normally then glazed, a process in which a thin glass surface is added to the piece. The chemistry of glaze formation is basically that of forming glass. However, the glass must have the proper viscosity so that it flows to completely cover the ceramic surface, yet not run off during the firing cycle. I t must also have a certain coefficient of thermal expansion such that it does not crack when cooled on the ceramic surface, or when subsequently reheated. The

glaze must he uniform and free of defects, and have the proper color and optical properties.

The major ingredient of a glaze is silica, usually obtained hv addina flint. a varietv of auartz. Alumina is necessarv in small amounts to increase thk viscosity of the molten It is incorporated hv adding clav or fe lds~ar . A flux material . . is added lower the fusion temperaturiof the silica. Those commonly used are oxides of the alkali or alkaline earth metals, or of lead, zinc, antimony, or boron.

The lead oxides have many excellent qualities as fluxing agents. However, the toxicity problem requires special han- dling techniques and the finished product should he given an acid leach test prior touse with foods or beverages. (6, 7) Li- tharge or lead (11) oxide and "red lead," Pha04, can he used, hut the preferred form is "white lead." 2PbCO?.Ph(OH)q. ., , More recently, potters have been using lead silicates which are safer to handle due to their insoluhilitv. One interesting theory to explain the fall of the Roman mi ire is the graduz poisoning of the population by lead leached from pottery vessels hy the slightly acidic wine. WCTU members take note!

The glaze ingredients discussed previously provide a glass surface to a ceramic piece. However, other metal oxides or sot~rceaot'oxidesarea~ldt~~l to pro\,ide color. Most yli~zen~lors can Iw olnained wing r.nh sewn transition metals, vanadium through comer. The resulting colors are influenced hv the .. .. .~ ~

glaze composition and firing conditions (8). The use of cad- mium and selenium together provide a red glaze due to a combination of CdSe and CdS. This combination, however, is not suitahle for tableware due to toxicity problems.

The chemistry of glass is an extension of the ceramic glaze discussion. The melting point of silica (1710°C) isreduced to about 700°C by the addition of Na2C03 and CaC03. Carbon dioxide is evolved and a complex mixture of sodium and cal- cium silicates, with excess silica remains. This is commonly referred to as lime glass and is produced in great quantities for windows and hottles.

"Stained glass" is hased upon the same metal oxides used to color ceramic dazes. Selenium is used also in the colloidal state for a ruhy tint, and colloidal gold can produce red, pur- ple, or hlue. depending unon the oarticle size nresent. .. .

The chemistry of paints prohdes an entry to organic chemistry and an excellent film is available that presents an interesting historical introduction.

The oil paints provide a basis for the discussion of linseed or other vigetahli oils as the vehicle, including oxidation and polymerization reactions. Certain metal compounds can he added to increase the rate of drying of the 03, or some pig- ments provide the same effect. The toxicity of certain paint ingredients is discussed, especially the use~of some solvents in poorly ventilated art studios (9).

Temoera naints are hased unon a vehicle that is an oil-in- . . water e ~ n u l h n , usuitlly stnl)dized by a natural gum matw~al The-r i)a~nts can he diluted w ~ t h wntpr ~ I I I rlrv to hecome water &soluble. The original tempera paints uied egg yolk diluted with water as the vehicle. '

\Vater-color paints are simply aqueous suspensions of finely gnn~nd pigments, stabilized d t e n by gum arahic. O ~ h e r ma- terials are usually added such as a plasticizer like glycerin to improve the pigment working properties, a preservative like phenol to prevent mold formation, and a wetting agent to improve spreading on the paper.

The new acrvlic uaints have become verv nooular and . . " . . provide the advantages associated with an aqueous rather than oil medium. The vehicle is a latex emulsion, containing polymers (and copolymers) such as polystyrene, polyhutadi- ene, polyvinylacetate, and polymethyl-methacrylate. Pig- ments are incorporated with the aid of dispersing agents. Other additives include defoaming agents, pH remlators, and .. .. . . mildew inhibitors.

The fresco process for mural painting dates hack to a t least 1100 B.C. Michelangelo was a master of this difficult tech-

Volume 56. Number 1. January 1979 1 31

The final experiment deals with air pollution and its effect on statuary. Oxides of nitrogen, phosphorous, and sulfur were generated and dissolved in water, noting the change in pH of the solution. Bits of limestone were placed in these solutions and allowed a sufficient period for change to occur.

Conclusion

There are many applications of chemistrv in the numerous an meas, and thus si&fi,snt ~ ~ p ~ o r t u n i t i e ~ e x i s t fbr chrmists to interact wi th a r t i s t s . Teach~nr a course such as discussed ha-: been both rewardmi: and interesting. It a p p n r s that the horiems d t h e studen1.i und instructor h w e been expanded in a unique manner, and it is hoped that new insightsgained will further their creativity.

A chemistrv course of this tvue mav not he feasible at all . . institutions. one necessary requirement is an .+kt Department willing to support such an endeavor. It is hoped that others will recognize the value of this cooperative effort and be willing to venture forth with their own unique talents.

Literature Cited (1) QuoteinCh#m. Eng. News. 26. 17 July 1975). (2) 0gren.P. J.,andBunse,D.L., J. CHEM.EOUC.46.681 (1971). I31 Oma, MsryViqinia.0. S. ll.,J. CHEM. EDUC.,53,638 (19761. (41 Feller. R. L.. J. P d n t Tech.. 44.51 (1972). (61 Johnwn, B. B.,andCsirnn,T.,Anoi. C h ~ m . , 44, #I , 24A (1972lsnd #2,30A (1972). (6) Lawrence. W. G.. "Ceramic Science for the Potter."Chilton BookCn., New Yak , 1972.

" "rr p.

17) Smith. J. F . '"Fact. About Lead Glazes for Art Pottersand Habbyistr" (pamphlet). Iasd lndnstriesAssoe.,lnc.. 1971.p. 5.

18) Cich0wski.R. S.,J. CHEM. EDUC.,52,616 (1975). (9) Siodlocki, J . T . J . Amer Med Amoc., 204.1176 (1968).

General References Pading, L., and Haward, R., "The Architecture of Molecules." W. H. Freeman and Co.,

San Francisco, 1964. Patton, T. C., IEdrtor), "Pigment Handbmk." John Wiley and Sons, Inc, New York,

1973. Preuss, H. P., "Pigment. in Paint: Noyos Data Cow. Park Ridge, New Jersey, 1974. Nelson, G. C.."Cermics:APatteis Handbmk:3dM., Holt,Rinehartand Winaton. Inc,

Now York, 1971. Rhodes. D., "Clay and Glazes for the Potter.)'Z Ed., Chilton Book Co., New York, 1973. Doerner, M.. "The Materials of the Artist and Their Use in Painting," 2nd Ed.. Hsrmurt,

Bra- and Co., New York. 1949. M a w , R.;'The Artist3 Handbmk ofMatuia1s and Te~hniquu." 2"d Ed.. The VikingPrear,

New York, 1966. M a w . R., "The Painter's Craft," 2nd Ed., D. Van Noatrand and Co., Inc., N e w York,

>ace

"OyePlsnt.sndDyeing."Plant.and Gsrdena,Vol. 20. No 3.. 1964. Cl'hiacan be pur .had for$1.50 fromtheBmoklynBotanicGarden, 10W Washington Ave.. Brwklyn,N.Y. 11225).

"Natural Plant Dyeing.)' Plants and Gardens, Vol. 29, N o 2,1973. (This csn be purchard for $1.50from theBrooklyn BotanieGsrden, 1WO Wa~hingtonAue.,Braoklyn. N.Y. 11225).

Grae, I., "Nature's Colors: Dyes from Plant..)' Maemillan Publishing Co., New York, 1974.

Rys, P., and Zollinger, H., "Fundamentals of the Chemistry and Applications of Dyes: Wiley-Interscienco.New York. 1972.

Christensen,H. E.,and Luginbyh1.T. T. 1Edilorsl;'TheTorieSuhstan-List:U.S.Dept of Health, Education end Welfare, National Institute for Occupational Safety and Health 1974 ~~~~~~~~,~~~~

Merck Index, 9th Ed., Merck and Co., Inc.. Rahway, New Jeraoy, 1976. Sax. I., "Dangerous Properties of lndustrisl Materials," 3rd Ed., Lifton Educ. Pub., 1973.

Film

"Paint: Film No. 12016, Shell Film Library, 1433 Ssdlier Cir., W. Dr., Indiampolis, Ind. 46239, (There is no chawe ffo its "a).

V o l u m e 56, Number 1. January 1979 1 33