Carol LeBaron Chemistry and Art February 21-23, 2005

1. Carol LeBaron Chemistry and ArtFebruary 21-23, 2005

2. My work is a combination of ancient clamp resist techniques and new technology

3. Chemistry Lab

6. Resist Dyeing

7. Two Examples of Clamp Resist with Folding

9. “Larkspur”

10. Removing the Dyed Piece

11. Placing in the Rinse Tank

14. This piece changed color on the loom and in the computer through fortuitous accident

15. Leonardo da Vinci, Mona Lisa (fifteenth century) • In the Late Renaissance the distinction between art and science was not synonymous with that between intuition and rationality • Scientists were chroniclers of antique knowledge and theory • Artists were valued for skill, and painters were as much chemists as artists

16. “vulgar chymists” • “It has long been recognized that one of the “problems” of chemistry before the eighteenth century was its status as a practical or technical art rather than a branch of natural philosophy. The low status of chymistry as determined by its uses amongst low technical appliers militated against its acceptance by many natural philosophers”(Robert Boyle, The Sceptical Chemist, 1665) • “vulgar chymists” included cheats who sought to profit from faked alchemical transformations as well as “laborants” such as dyers, distillers, and apothecaries who did not have any theoretical knowledge.

17. Resist dye on textiles has been known as early as 2,000 BCE

18. Nasca Wari textile, 400 CE Resist dyed

19. Mineral Pigments • In inorganic compounds such as crystalline minerals and salts, metal atoms are ions and bear a positive electric charge • They are tough and difficult to grind • Transition metals have ions whose resonant frequencies fall in the range of visible light • It is dependent on the other chemicals with which it is compounded Altamira artists created sculptural effects by painting the animals over and around the rock formations. 12,000 BCE Used red and brown ocher to create the color

20. Prehistoric Pigments at Lascaux, France c. 15,000 BCE • Iron oxide hematite crystallized with water • Green earth from aluminosilicate clays celadonite and glauconite • Black from charcoal • Brown from manganese oxide • White from chalk and ground bones • Violet from manganese

21. Rearranging Electrons • It was not long after the invention of fire that artist chemists discovered ways to make color • Heat may alter the chemical structure of a mineral • Examples • Heating blue copper sulfate to drive out water molecules turns it almost white • When white lead is heated water and carbon dioxide leave behind lead tetroxide(“red lead”)

22. Organic Color • The colorants in living organisms are organic compounds • Discrete molecules containing several dozen atoms each with backbones of linked carbon atoms • Until the nineteenth century all dyes were natural products • Were also used for inks and paint(lakes)

23. Natural Dye Materials • Indigo was the frothy extract of a weed • Tyrian purple came from shellfish • Madder red came from a root • Cochineal came from an insect

24. Today almost all dyes are synthetic organic molecules. • Their carbon skeletons are custom built by industrial chemists. • Barely a dozen natural dyestuffs were stable enough to be useful in the ancient world • We now have over four thousand synthetic dyes

25. Why Dyes were Developed: Colored garments indicated social hierarchy • The demand of powerful rulers for rich cloths influenced the development of dyes • Dyes are bound into cloth by mordants substances that help attach the coloring agent(usually an organic compound) to the fibers Timurid court, 12th century

26. The textile trade stimulated developments in dye chemistry • Alum production was a large medieval industry The capture of Constantinople in 1453 by the Turks cut off trade and led to an alum shortage • Later alunite(mineral form of potassium alum) was found in papal territories in Italy • The Arabs purified alum with ammonia-containing stale urine to remove the iron salts Shah Jahan c. 1600

27. Theophilus describes: • “Grind some minium or cinnabar with this(poppy) oil on a stone without water, spread with a brush on the panels that you want to redden and dry them in the sun” • They had trouble drying them because they pressed their oil in an olive oil press The female painter Thamar with assistant grinding colors behind her

28. Royal Purple and Commerce • The era of modern dyes began with a purple to rival ancient dyes • The influence of nineteenth century chemistry is more dramatic and has farther reaching effects on dye manufacture than pigments

29. So what are dyes and how do they work? To understand, we have to begin with light

30. Light is made up of bands of varying wavelengths

31. Reflection • White can only be broken up by prisms or by colorants such as pigments and dyes • This surface has no colorant so the light is reflected

32. It can be fully absorbed by the surface

33. Or a transparent surface may let all of the light pass through or a colored surface may absorb part of the spectrum

34. Bands of light mix together to produce lighter colors

35. A “blue” surface absorbs red, orange, and yellow light

36. A “yellow” surface absorbs blue and violet light

37. The pigment primaries absorb and reflect different combinations of colored light

38. Interference: the kind of surface light hits can affect the way light waves behave

39. Structural Color: Materials that light hits can cause a multitude of effects • Iridescence • Luminescence • Refraction • Diffraction • Fluorescence • Phosphorescence

40. The nature of fiber affects the way light appears

41. Fiber reflects, refracts, absorbs and diffuses

42. The unique color properties of fiber depend on the interaction of fabric structure, dye application, and light

43. Pigments and Dyes • A dye is a colorant that goes into solution or dissolves. Dye particles break apart into single molecules • Pigment particles remain clustered together in suspension • Dyes have a chemical affinity for fiber but pigments do not Pigment particles Dye molecules

44. Pigment molecules carry their own color They do not unite with fiber molecules chemically and must be fixed to the fibers with bonding agents In man made fibers pigments can be mixed into the fiber solution before it is formed Dyes migrate out of the solution, are absorbed into the fiber, and diffuse from the surface of the fiber toward its center. There they either: Bond chemically with fiber molecules OR React chemically with fiber molecules to produce permanent, enlarged colored fiber molecules Both situations are permanent Pigments and Dyes

45. Dye molecules must be firmly fixed to fiber Chain fiber molecule Dye molecules

46. A negative dye molecule links with a positive fiber molecule at a dye site. The process is affected by surface charge, temperature, and agitation. Different fibers have different numbers of dye sites. Wool fiber has 1000 dye sites, silk has 100, and cotton has less than 10

47. Assembly of dye molecules at the fiber surface • When soaked in water all fibers acquire an electric potential or surface charge • Cellulosic fibers acquire negative charges • Protein fibers acquire both positive and negative charges, depending on the pH of the water • Acid solutions help break down protein fibers to allow dye sites access to the dye • Cellulose fibers must be soaked in alkaline solution • Salt is used to set up electrical movement that initiates the movement of dye molecules in search of a resting place on the fiber

48. Once the dye molecule enters the fiber, it has a a chemical reaction with it. It is enlarged, which prevents its exit.

49. Color is produced when a divided molecule is united.

50. Acid Dyes • Used mainly on wool, silk, and nylon* • They have acid chemical groups in their dye molecules • They use an acid dye bath to produce the chemical reaction • Reaction involves acid, salt, heat, agitation, and time • Amount of acid and rate at which it is added affects the rate at which the dye bonds • Salt slows the bonding process, helping the dye color the fiber evenly. It attaches to the dye first.