con chem

• Dyes


  A substance used to impart color to a substrate when applied in solution from either aqueous or organic solvents
• Dyes


  Water soluble, direct affinity, no binding agent required, translucent, diffusions ON the fabric
• Pigments


  100% water insoluble, no direct affinity, binding agent required, opaque, diffusions IN the fabric
• Dyes vs Pigments


  • Key Differences: Water soluble vs insoluble, direct affinity vs no affinity, binding agent required vs not required, translucent vs opaque, diffusions ON vs IN the fabric
• Natural dyes used in ancient age


  • Alizarin
  • Indigo
• Alizarin


  Red dye extracted from the roots of the madder plant, Rubia tinctorium
• Other red natural dyes


  • Kermes, obtained from Coccus ilicis
  • Cochineal, obtained from Dactylopius coccus
• Indigo


  Blue dye obtained from the leaves of woad herb Isatis tinctoria, and the indigo plant Indigofera tinctoria
• Tyrian purple


  Derivative of indigo, extracted in very small amounts from the glands of the Murex brandaris snail in the Eastern Mediterranean
• Tyrian purple


  Also called royal purple, kings, emperors, and high priests had the exclusive right to wear garments dyed with it
• The dyes used for garments were proportionate to the wealth or importance of the people. Wealthy people wore brightly hued colours, while the lower class wore clothes in the shades of white/brown
• Mordants


  Naturally occurring water soluble metallic salts which create a bond between the dye and the fiber
• Mordants are used to create colorfast dyes
• Without a mordant, dyes are unlikely to retain any color on the fabric
• Substantive dyes/Direct dyes


  Dyes that don't require mordanting
• Traditional mordants


  • Alum
  • Copper
  • Tin
  • Iron
  • Chrome
• Mordants are used to vary the colors produced from a single dye
• Colors produced with alizarin and different mordants


  • Turkey red with aluminum hydroxide
  • Violet with magnesium
  • Purple-red with calcium
  • Blue with barium
• Decline of natural dyes


  Transportation delays, affected by whims of nature and dye maker's skills, complex and time consuming extraction process
• William Henry Perkin discovered the first synthetic dye - mauveine - in 1856 while searching for a cure for malaria
• Following Perkin's discovery, other chemists began experimenting with coal tar derivatives to create new synthetic dyes throughout the late 19th and early 20th centuries
• Synthetic dyes quickly gained popularity due to their vibrant colors, colorfastness, and versatility, replacing natural dyes
• Coal tar


  Byproduct of coal processing, abundantly available during the Industrial Revolution, contains aromatic hydrocarbons that are essential precursors for synthesizing synthetic dyes
• Advantages of synthetic dyes over natural dyes


  • Wide range of colors
  • Consistent color intensity and shade
  • Lower production costs
  • Better colorfastness and durability
  • Easier to control and scale production
  • Readily available raw materials
• Disadvantages of natural dyes

  • Limited color palette
  • Variability in color intensity and shade
  • Higher production costs
  • Variable colorfastness and durability
  • Time consuming processes
  • Dependent on seasonal and regional factors
• Dyes possess color


  Because they absorb light in the visible spectrum, have at least one chromophore (color-bearing group), and have a conjugated system
• Chromophore


  Controls the color of the dye, contains conjugated double bonds that allow electrons in the molecule to move more freely
• Auxochrome


  A functional group attached to a chromophore that can modify the color intensity by affecting the distribution of electrons within the chromophore, leading to a shift in the wavelengths of light absorbed by the chromophore
• Both chromophores and auxochromes are crucial for determining a dye's final color
• Dye retention


  The ability of a dye to stay attached to a material
• Dyes


  A substance used to impart color to a substrate when applied in solution from either aqueous or organic solvents
• Important chromophores include...
• Dyes


  Water soluble, direct affinity, no binding agent required, translucent, diffusions ON the fabric
• Additional notes...
• Pigments


  100% water insoluble, no direct affinity, binding agent required, opaque, diffusions IN the fabric
• Dyes vs Pigments


  • Key Differences: Water soluble vs insoluble, direct affinity vs no affinity, binding agent required vs not required, translucent vs opaque, diffusions ON vs IN the fabric
• Dyes possess color


  • because they absorb light in the visible spectrum
  • have at least one chromophore (color-bearing group)
  • have a conjugated system
• Natural dyes used in ancient age


  • Alizarin
  • Indigo
• Alizarin


  Red dye extracted from the roots of the madder plant, Rubia tinctorium
• Dye molecules contain 2 groups


  • Chromophore - controls the color of the dye, contain conjugated double bonds that allow electrons in the molecule to move more freely
  • Auxochrome - a functional group attached to a chromophore that can modify the color intensity, affecting the distribution of electrons within the chromophore that can lead to a shift in the wavelengths of light absorbed by the chromophore