Pigment

Lightfast Pigments

Natural coloring matter of highest lightfastness - permanent substances used for art painting - pigments in form of a dry powder mixed with binder that constitutes a paint or ink. I usually use pigments as paints: dispersed in natural gum or polymer.

Pigments are colored or achromatic organic or inorganic solids. They are usually insoluble chemically stable and retain a crystal or particulate structure.

Inorganic and Organic Pigments

Inorganic

Inorganic pigments have excellent light and heat resistance and weatherability. Inorganic pigments include titanium dioxide, carbon, iron and chromium oxides, mixed metal oxides, manganese oxide, cadmiums, lead chromate,  ultramarines, iron blue, chrome green, etc.

I use these single-pigment paints based on inorganic pigments, from more often to less, grouped by main chemical element:

  1. Iron oxide pigments: sanguine, venetian red, red oxide, raw and burnt sienna, raw and burnt umber, yellow ochre, prussian blue, black iron oxide.
  2. Carbon pigments: natural charcoal, graphite.
  3. Titanium pigments: titanium white.
  4. Sulfur pigments: french ultramarine, ultramarine green shade and violet.
  5. Cadmium pigments: cadmium yellow, deep red, scarlet.
  6. Cobalt pigments: cobalt violet, blue, cerulean, turquoise.
  7. Manganese pigments: manganese violet.
  8. Chromium pigments: viridian.
  9. Zinc pigments: zinc white.
  10. Lead pigments: naples yellow.

Organic

I do not use organic pigments with biological origins (like alizarin, gamboge, rose madder, indigo, etc.)

However, I use a few non-biological organic pigments (like quinacridones and phthalos).

Organic pigments have wider range of bright colors, and many have excellent light and solvent resistance. They are divided into two groups:

  1. Azo pigments includes monoazo yellow and orange, di-azo, azo lake, benzimidazolone, bis-azo, naphthols, metal complexes.
  2. Non-azo pigments, heterocyclic and fused ring, include phthalocyanine, quinacridone, perylene and perinone, thioindigo, anthraquinone, dioxazine, isoindolinone and isoindoline, pyrrole, triarylcarbonium, quinophthalone.

Color Index Code

By the color classification method, pigments are coded:

pigment yellow (PY), orange (PO), red (PR), violet (PV), green (PG), brown (PBr), black (PBk), white (PW), metal (PM).

Pigment Lightfastness

I use only permanent and very lightfast pigments, blue wool 7-8 or ASTM I.

Blue Wool and ASTM Standards

  • Blue wool (BW) lightfastness levels: from 8 (extremely lightfast) down to 1 (fugitive).
  • ASTM - American Society for Testing and Materials - lightfastness categories: from I (excellent) to V (poor).
  1. BW 7-8 = I. Excellent lightfastness, suitable for artistic use, will remain unchanged for more than 100 years of light exposure.
  2. BW 6      = II. Very good lightfastness, suitable for artistic use, unchanged for 50 to 100 years with proper display.
  3. BW 4-5 = III. Fair lightfastness, impermanent, unchanged for 15 to 50 years, last longer if used full strength or with extra protection from light.
  4. BW 2-3 =  IV. Poor lightfastness, fugitive, begins to fade in 2 to 15 years, even with proper mounting and display, not suitable for artistic use.
  5. BW 1       = V. Very poor lightfastness, fugitive, begins to fade in 2 years or less of light exposure, not suitable for artistic use.