Unit
- Pigment: the finely ground colored particle suspended in paint that determines hue, opacity, and lightfastness; pigments can be organic (carbon-based, often more transparent) or inorganic mineral compounds (often more opaque and stable over time).
- Binder: the medium that holds pigment particles together and adheres them to a surface; in acrylic paint the binder is an acrylic polymer emulsion, while oil paint uses drying oils like linseed, and watercolor uses gum arabic.
- Vehicle versus binder: the vehicle is the carrier that keeps paint workable before it dries or cures, such as water in acrylic, while the binder is what remains and hardens permanently once that vehicle evaporates.
- Opacity and transparency: pigments are classified by how much they obscure the surface beneath them; opaque pigments like titanium white cover completely, while transparent pigments like phthalo blue allow underlying layers or the canvas ground to show through, which matters for glazing techniques.
- Lightfastness rating: a standardized measure (often ASTM ratings I through III) indicating how resistant a pigment is to fading under prolonged light exposure; professional-grade paints list this rating on the tube, and artwork intended to last should prioritize pigments rated excellent or very good.
- Paint viscosity and body: heavy body acrylics hold brush marks and texture, while fluid or soft body acrylics self-level and suit smooth blending or pouring techniques; oil paint's viscosity varies by brand and can be extended with mediums.
- Tinting strength: some pigments, like phthalo green or quinacridone magenta, are extremely concentrated and will dominate a mixture even in small amounts, requiring careful proportion control during mixing to avoid overpowering a intended color.
- Student grade versus professional grade: student-grade paints use lower pigment concentration and cheaper fillers, resulting in less active color and reduced lightfastness, while professional-grade paints use higher pigment load for stronger, more consistent color across a range.
- Drying mechanism differences: acrylic dries through water evaporation and polymer coalescence, typically within minutes to an hour depending on thickness, while oil paint cures through oxidation, a chemical process that can take days for touch-dry and months to fully harden.
Design Principle
Principle: Material Transparency as a Compositional Tool
Definition: Choosing pigments based on their opacity or transparency allows a painter to control how much visual information from underlying layers remains visible, directly affecting depth and luminosity.
Application: Underpaint a shadow area with a warm transparent pigment like burnt sienna, then apply a thin transparent glaze of ultramarine blue over it once dry. The warm undertone glows through the cooler glaze, producing a shadow that reads as luminous rather than flat and dead, a technique long used in figurative and landscape painting.
Quick Revision
- Pigment determines hue and lightfastness; binder determines adhesion and drying behavior.
- Acrylic binder is a polymer emulsion; oil uses drying oils; watercolor uses gum arabic.
- Opacity versus transparency affects how layers interact, critical for glazing.
- Professional-grade paints carry higher pigment load and better lightfastness ratings than student grade.