PR 274 – ponceau 4R

Manufacturer/ product code:  Kremer / 42300
Chemical Description:  cerium sulfide
Color: red
Color Index: PR 274
Date:  —

PR 274 – Ponceau 4R is a synthetic organic red colorant belonging to the monoazo dye family. Chemically known as a sulfonated azo compound, Ponceau 4R is more widely recognized as a soluble dye (food additive E124) than as a traditional pigment. When converted into an insoluble substrate-bound form (lake pigment), it may be classified under the Colour Index as PR 274, although its use as a true artists’ pigment is relatively limited.

From a chemical perspective, Ponceau 4R consists of an azo (-N=N-) chromophore linking aromatic rings substituted with sulfonate groups, which confer high water solubility in its dye form. As with many azo dyes, this structure produces a vivid, bright red hue with a slight orange undertone but also results in limited lightfastness compared to modern high-performance organic pigments such as quinacridones or pyrroles. Exposure to light, especially UV radiation, can lead to fading and chromatic shifts over time.

Historically, Ponceau-type dyes found application in textiles, inks, food coloration, and early commercial paints, particularly where intense color and low cost were prioritized over permanence. In lake pigment form, PR 274 may be encountered in decorative coatings, prints, or historical objects rather than in contemporary professional artists’ materials.

In analytical and conservation contexts, PR 274 is of particular interest due to its organic, dye-based nature. Techniques such as UV–Vis spectroscopy, Raman spectroscopy, or HPLC are often required for confident identification, as XRF provides little diagnostic information.