Caput Mortuum Violet

Caput Mortuum Violet is a synthetic iron oxide pigment powder (PR101) in a deep reddish violet, made by strongly heating iron sulfate with a little salt. Opaque, lightfast and stable in mixtures, it gives the cool purple-brown of caput mortuum in oil, acrylic, egg tempera, watercolor, gouache and fresco.

Key facts

• Color: deep reddish violet (purple-brown)
• Pigment type: Synthetic inorganic pigment (iron oxide)
• Colour Index: PR101 (C.I. 77491)
• Composition: iron(III) oxide, Fe₂O₃, in relatively large crystals of 2–6 µm (supplier data)
• Origin: synthetic
• Also known as: Mars violet
• Opacity: opaque
• Lightfastness: 8 of 8 on the Blue Wool Scale (supplier data)
• Chemical resistance: alkali 5/5, lime 5/5 (supplier data, 5 = best); stable in weak acids, dissolved by strong mineral acids
• Suitable for: oil, acrylic, egg tempera, watercolor, gouache, fresco (lime), ceramics
• Packaging: 25 g jar · 1 kg bag

How to use

Mix the powder into linseed oil, egg yolk, gum arabic or acrylic medium with a palette knife or muller; for fresco, grind it in water and paint into fresh lime plaster. Grind gently: its violet tone comes from relatively large particles, and heavy grinding shifts it toward red. It covers well, so add it to mixtures in small amounts. With white it gives soft mauves; with ultramarine, deep violet shadows.

About Caput Mortuum Violet

Red iron oxides look more violet the larger their particles: around 1–5 µm the color moves from red toward purple. The supplier makes this pigment by calcining iron sulfate (copperas) with 3–5% common salt; without salt, the same process gives English red. The supplier names specular hematite as its natural counterpart. Violet iron oxides of this kind are also sold as Mars violet.

Safety

Handle dry pigment with care: avoid breathing the dust and contact with eyes. Wear a dust mask (FFP2/N95) and gloves when working with the powder, work in a well-ventilated area and wipe up spills with a damp cloth. Do not eat, drink or smoke while working; wash your hands afterwards. Keep away from children and pets. For artistic and technical use only — not for cosmetics, food or tattoos.

FAQ

How does it differ from Caput mortuum?

Caput Mortuum Violet is a synthetic iron oxide (PR101) with a cooler, more violet tone. Our Caput mortuum is made from natural iron oxides (PR102) and is browner.

Is it lightfast and lime-proof?

Yes. The supplier rates it 8 of 8 for lightfastness and 5 of 5 for lime and alkali resistance.

Is it toxic?

No specific hazard is known: iron oxides are considered non-toxic. Like any fine powder, the dust can irritate the eyes and airways, so follow the precautions above.