This page describes how entries are selected, researched, verified, and labelled. It is the long answer to how do you know.
How colors are selected
A color qualifies for inclusion when three conditions are met. First, the name must be in documented historical or commercial use, not a one-off invention by a hobbyist palette, and not a marketing rename of an existing pigment. Second, there must be at least one primary or near-primary source that establishes the color's identity: a treatise, a patent, a conservator's analysis, a museum catalogue, or a peer-reviewed paper. Third, there must be something worth saying about it beyond the name, a story or a controversy that earns it a paragraph.
The launch corpus comprised two hundred and fifty entries, chosen to balance ten hue families and seven eras (Ancient, Medieval, Renaissance, Baroque, Industrial, Synthetic, Modern) so the index reads as a cross-section of color history rather than a top-heavy collection of nineteenth-century chemistry. New entries are added regularly; the rate is set by editorial readiness, not by a quota. Each addition must meet the same three conditions as the original corpus.
How each entry is researched
Each entry begins with a working hypothesis: a single sentence describing what makes this color worth a paragraph. From there the work is in three passes.
The first pass is documentary. Primary sources where they exist (Pliny on Tyrian purple, Cennini on lead-tin yellow, the Roberson archive on mummy brown), read in modern critical translations. Where the primary source is fragmentary or unreliable, the best modern synthesis is used as the spine; Bright Earth (Philip Ball), Pigment Compendium (Eastaugh et al.), and the Getty Conservation Institute's published analyses are recurring references.
Wikipedia and other wiki-family pages are not accepted as a source, or as evidence that a claim is true. A wiki article may point toward a primary source, but that primary is then located and cited directly. A claim counts as verified only when a non-wiki source confirms it: a museum or conservation database, peer-reviewed scholarship, an institutional or government record, an established news organisation, or an original document. A claim that cannot be sourced that way is softened, cut, or marked as interpretation.
The second pass is technical. Chemical formulae are cross-checked against the most recent edition of the Pigment Compendium or the relevant Colour Index designation. Hex values are derived from a combination of standardised reference samples (Munsell, Pantone, NCS where applicable) and, where the color has no modern reference, from the conservator's published spectrophotometry of the best-preserved historical sample. Hex values for purely historical pigments are approximations; the entry says so.
The third pass is editorial. Each entry is rewritten until it can be read in under three minutes and until every claim of consequence can be tied to a citation. Citations are pruned to between three and seven per entry: enough to verify the central claims, few enough to be read.
What the source labels mean
Each entry carries a single source category:
- Mineral: ground from ore, stone, or earth. Azurite, lapis lazuli, ochre, vermilion.
- Plant: extracted from leaves, bark, roots, or wood. Indigo, madder, brazilwood, weld.
- Animal: derived from a vertebrate or invertebrate source other than mollusc or insect. Sepia, bone black, mummy brown.
- Insect: derived from a scale-insect dye. Cochineal, kermes, lac.
- Mollusc: derived from murex or related shellfish. Tyrian purple.
- Synthetic: produced by chemical synthesis, including coal-tar dyes, cadmium pigments, and modern phthalocyanines.
- Digital: no physical pigment; a color named and used primarily in digital or proprietary contexts (sRGB-only colors, brand-protected hues).
What the status labels mean
Each entry carries a single status:
- Active: currently manufactured and sold, in artist or industrial grades.
- Restricted: still manufactured but subject to regulatory limits in one or more jurisdictions (REACH, EPA, sumptuary protected, etc.).
- Discontinued: no longer commercially produced. May still appear in conservation contexts or as old stock.
- Historical: produced only in the historical record; no commercial manufacture in the modern period.
The status is a snapshot at time of writing. Status changes are logged on the entry.
What the tier labels mean
Each entry carries a single tier, the editor's judgment of how interesting its story is, not of the color's historical importance and not of its sourcing:
- Unmissable: the stories worth reading first, a strange history or a fact that reframes the color.
- Strong: a real story, well documented, a notch below the standouts.
- Good: worth its paragraph, without a hook to pull it forward.
Every entry clears the same citation bar whatever its tier. Tier drives two things on the site. The weekly picks on the homepage rotate through the unmissable set, three each week. The spectrum strip on the browse page lists unmissable first among each hue's representatives. The daily featured color ignores tier and rotates through the whole catalogue.
How curatorial decisions are made
When a color has several plausible names (vermilion, cinnabar, Chinese red, minium), the catalogue uses the name most often found in modern English-language conservation literature, and lists the alternates in frontmatter. Where two pigments are commonly confused (minium and cinnabar, both red, both lead-or-mercury-based), each gets its own entry and cross-links to the other.
When a color has no first-documented year (earth pigments older than recorded history, dyes whose origin is reconstructive), the entry uses a year range and labels the date "approximate." A null year is preferred to a fabricated one.
Where two laboratories disagree, the entry favours the more recent peer-reviewed analysis, names both, and cites them in order of recency.
Corrections
Errors of fact are logged, dated, and noted at the foot of the entry. Substantive corrections are also surfaced in the Journal. If you find a mistake or a claim that does not hold up, email [email protected]. The catalogue's value is its citations; the citations' value is that they have been checked.