Marbler's Guide - Black Pigments

Black Is Not Black: The Chemistry of Darkness

Ask a painter to mix black, and they'll likely reach for a tube of paint labeled "black." But open the pigment reference, and you'll discover three entirely different black pigments—each with contradictory chemical personalities and marbling behavior.

What is a Pigment?

Gouache and acrylic both contain three elements:

1. Pigment — the colored powder
2. Binder — what holds it together (gum arabic for gouache; polyacrylates for acrylic)
3. Water and additives

After painting, gouache remains water-soluble; acrylic becomes water-resistant.

In marbling, the paint forms an impossibly thin floating film on the solution surface. Tiny chemical forces govern everything. Each pigment responds differently.

Three Black Pigments: One Name, Three Natures

1. Lamp Black / Carbon Black (PBk7)

Chemistry: Nearly pure elemental carbon (~99% C), produced by incomplete combustion of organic materials. Soot, essentially.

History: One of humanity's oldest pigments—used in cave paintings at Chaucer (32,000 years ago) and in China for ink calligraphy for millennia.

Chemical properties:

• Extremely stable; doesn't react with other pigments or water chemistry
• No ions; no electrical charge
• Uniform, amorphous structure with fine granulation
• Recommendation: USE THIS. It's the marbler's ideal black.

Marbling behavior:

• Stays exactly where applied
• Creates sharp, clean edges
• Transfers perfectly to paper
• Doesn't muddy adjacent colors
• Preserves the clarity of patterns

2. Ivory Black / Bone Black (PBk9)

Chemistry: Made by heating animal bones under limited oxygen. Contains ~14% carbon + 70–80% calcium phosphate (Ca₃(PO₄)₂).

The problem: The calcium phosphate dissociates into Ca²⁺ and PO₄³⁻ ions in water.

Marbling behavior:

• Ca²⁺ and PO₄³⁻ are highly reactive with the surfactant balance of marbling solution
• Paint frays at the edges—lines become fuzzy
• NOT RECOMMENDED for marbling.

3. Mars Black / Iron Oxide Black (PBk11)

Chemistry: Synthetic iron oxides (Fe₃O₄). Magnetic; reactive.

The problem: Iron oxides are surface-active particles. They interact with water and surfactants.

Marbling behavior:

• After a few seconds on the solution, the paint clumps and frays
• Colors muddy together instead of maintaining distinct borders
• Patterns become smeared and chaotic
• NOT RECOMMENDED for marbling.

Paint Brands: Know Your Black

Winsor & Newton:

• Publishes full pigment codes on each tube
• Professional lines use PBk7 (excellent)
• Budget "Cotman" line may substitute cheaper blacks
• Check the label

Royal Talens:

• Their blacks tend toward PBk9 (Bone Black) — problematic for marbling
• Verify on artistpigments.org before purchasing

Turkish Marbling Paints (Ebru Boya):

• Specifically formulated for marbling
• Higher pigment concentration, less binder
• Granulation optimized for carrageenan
• Drawback: requires pre-soaking (days) and alum-treated paper
• Advanced technique

Schmincke, Golden, Liquitex:

• Generally excellent pigment transparency
• Schmincke Akademie line provides full codes
• Golden and Liquitex publish detailed technical data sheets
• Any of these blacks are marbling-safe

Practical Conclusions for Your Workshop

1. Always verify pigment codes using artistpigments.org
2. For black, insist on PBk7 (Lamp Black). No exceptions.
3. Experiment systematically — change one variable at a time
4. Keep notes — record which paint, which batch, which results
5. Turkish paints are advanced — master inorganic gouache first
6. Test new paints on small solutions before committing to large batches

The 32,000-Year Lineage

Carbon was a pigment in Chauvet Cave (32,000 BC). It was a pigment in Gutenberg's printing press. It remains PBk7 today—the same chemical substance, the same perfect inertness, the same clarity.

Chemistry doesn't lie. Choose the right pigment, and marbling becomes predictable, even elegant.

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In the next issue: What causes fraying? What causes bleeding? The complete troubleshooting guide to marbling mistakes.