What this calculator does

This tool maps the complete colour space produced by blending iron oxide red, yellow and black pigments in Portland cement at the industry-standard loading of 3% by weight of cement. Every disc in the triangle is a unique, reproducible formula. The mathematics is barycentric — each colour is a precise weighted combination of the three primary iron oxide pigments. The formulas read directly into a laboratory notebook or production batch record.

Built on physical laboratory work

The triangle shown above was cast by hand over a decade ago — 231 individual cement discs, each pigmented to a unique formula using Bayferrox iron oxide pigments on a grey Portland cement base, weighed on calibrated digital scales to 0.01 gram accuracy. The calculator recovers and extends that mathematics digitally, adding white cement simulation and precision sub-triangle drill-down to any position in the colour space.

Professional guidelines

Before you mix — six rules from the bench

These are not disclaimers. They are the difference between a reproducible professional result and an unrepeatable accident. Every rule here comes from bench experience with pigmented cement, not from a data sheet.

The sand speaksAggregate is not a neutral carrier. A warm golden sand shifts every colour toward amber before a gram of pigment is added. A cool grey river sand does the opposite. White silica sand is the only truly neutral voice. Always specify your aggregate alongside your pigment formula — the two are inseparable.

Accurate scales are non-negotiable0.01 gram accuracy minimum. At 3% pigment loading on a 500g cement batch, a 0.5g weighing error produces a 3% variation in colour intensity. That is visible to the eye and it cannot be corrected after mixing. Consistent colour requires consistent measurement.

Hardware store oxides are not good enoughUnknown particle size distribution, no Certificate of Analysis, inconsistent iron oxide purity, variable batch-to-batch colour. A reproducible product cannot be built on an unknown raw material. Use industry-standard pigment suppliers only.

Use industry-standard pigment suppliersLanxess Bayferrox, Huntsman, Cathay Industries. These manufacturers provide known particle morphology, consistent calcination temperature, and a Certificate of Analysis with every batch. Specify micronized grades only — they disperse evenly and give consistent tinting strength.

Blacks are not all blackCarbon-enhanced blacks carry significantly higher tinting strength than standard iron oxide blacks. A 0.5% carbon black loading can achieve what 1.5% iron oxide black cannot. However carbon black behaves differently in cement chemistry. Know which black you are using and why before you calculate any formula.

3% pigment by weight of cement — industry standardAbove this threshold, colour return diminishes and compressive strength may be affected. The formulas in this calculator are based on this standard loading. Within the palette, reds have more visual impact per percentage point than yellows or blacks — the choice of red grade is the single most consequential decision in the system.

Master triangle — 21 rows · 231 colours

Bayferrox 110 red · iron oxide yellow · iron oxide black
White Portland cement · 3% total pigment by weight

Master disc size 13px Sub-triangle disc size 17px

↗ hover any disc to read its iron oxide formula · click to open a 91-disc precision sub-triangle

Red — Bayferrox 110

Yellow — iron oxide

Black — iron oxide

White Portland cement

Sub-triangle — 13 rows · 91 colours

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↗ hover any disc for its precise formula · 3 decimal place accuracy · formulas read directly into a batch record

Not all reds are the same

Within the Lanxess Bayferrox range, Red 110 and Red 130 share the same chemical classification — iron oxide red, Fe₂O₃, Pigment Red 101 — but they produce fundamentally different colour worlds in Portland cement. Bayferrox 110 is a fine-particle red produced by the Laux process at lower calcination temperatures. Its finer particle size shifts the apparent hue toward warm orange — the red of classical terracotta, of Roman brick, of Coade stone. Bayferrox 130 is calcined at higher temperatures, producing coarser particles and a distinctly cooler, blue-shifted red — precise, architectural, contemporary. The two triangles below use identical yellow, black and cement. Only the red differs. The consequence is systemic across every one of the 91 colour positions shown. The choice of red grade is judgement. Everything else in this system is mathematics.

Bayferrox 110 — orange-warm red

Fine particle · Laux process · warm yellow-orange shift
Preferred for terracotta, heritage restoration, garden ceramics

apex — rgb(212, 82, 42)

Bayferrox 130 — cool blue-red

Coarser particle · high-temp calcination · cool blue shift
Preferred for contemporary architecture and industrial applications

apex — rgb(139, 26, 42)

What shifts across the entire palette when you change the red: The buff zone moves from warm gold (110) to grey-mauve (130). The terracotta corridor shifts from luminous amber-red to a cooler, deeper sombre red. The burnt umber territory moves from warm chocolate to a cooler liver brown. The olive-sage zone along the yellow-black edge is largely unchanged — that territory is driven by yellow and black, not red. Hover both triangles to compare formulas at equivalent positions.

Iron oxide pigments in cement

Synthetic iron oxide pigments — red (Fe₂O₃), yellow (FeOOH) and black (Fe₃O₄) — are the industry standard for coloring Portland cement. They are alkali-resistant, UV-stable, non-toxic and permanently bonded into the cement matrix. Unlike organic dyes, they do not fade. The three primary oxides can be blended across a continuous colour space spanning terracotta, buff, umber, ochre, olive and slate — every earth tone used in architecture since antiquity.

White versus grey cement base

Grey Portland cement acts as a cool grey wash beneath every pigment, shifting colours toward muted, cooler tones. White Portland cement allows pigments to express their full chroma — terracottas become luminous, buffs become warm and clean, and the Coade stone buff range opens fully. For heritage colours, decorative concrete, cast stone and garden ceramics, white cement is almost always the correct base. Grey cement suits contemporary architectural concrete where cooler, more restrained tones are specified.

The barycentric colour triangle

A barycentric triangle places each pure pigment at an apex. Every interior point is a precise weighted combination of the three — its position encodes its formula. At 21 rows across, each step represents 0.15% pigment by weight, producing 231 unique formulas within a single triangle. Clicking any disc opens a sub-triangle that spans ±4 master steps around that point — effectively a 20× zoom into the colour neighbourhood, revealing 91 additional unique formulas within a 0.6% range.