Mars red transparent

Mars red transparent is a synthetic red iron oxide pigment powder (PR101) made of extremely fine particles, so it glazes instead of covering. It gives a clear, warm rust red in thin layers and is used for glazes, transparent shadows and warm underlayers in oil and acrylic, and for watercolor washes.

Key facts

• Color: warm rust red
• Pigment type: Synthetic inorganic pigment (transparent iron oxide)
• Colour Index: PR101 (C.I. 77491)
• Composition: iron(III) oxide, Fe₂O₃, as nanometer-size particles
• Origin: synthetic
• Also known as: transparent red iron oxide
• Opacity: transparent
• 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), lime and cement plaster, ceramics
• Packaging: 50 g jar · 1 kg bag

How to use

Transparent iron oxides are hard to disperse, because the tiny particles cling together in clusters. Mull the powder thoroughly with a glass muller, adding linseed oil, acrylic medium or gum arabic little by little, until the paint is smooth and free of specks. Apply it thinly over a light ground or a dry underpainting, and build depth with several glazes rather than one thick layer.

About Mars red transparent

Iron oxides become transparent when their particles are smaller than about 0.1 µm: such tiny needles, typically under 20 nm wide and 150 nm long, no longer scatter light. Transparent red is commonly made by heating transparent yellow iron oxide. Chemically it is the same Fe₂O₃ as opaque Mars red; industry uses it in wood finishes and car paints, where it also absorbs UV light.

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

What makes it transparent?

Particle size. Its particles are far smaller than those of ordinary iron oxide, so they let light pass instead of scattering it. The chemistry is the same as in opaque red iron oxide.

How is it different from Hematite and Venetian red?

All three are synthetic red iron oxide, PR101. Hematite and Venetian red are opaque grades for covering; Mars red transparent is made for glazing.

Is it lightfast?

Yes. The supplier rates it 8 of 8 on the Blue Wool Scale, and transparent iron oxides are known for excellent permanence.