Glaze

Glaze Colorant Calculator

Calculate oxide and stain additions to produce a target color in a glaze batch.

Updated May 2026

Base Glaze Batch Weight

Colorant

Color Intensity

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Results

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Enter your measurements above and click Calculate.

Colorant Percentage Ranges

Glaze colorants are metal oxides or carbonates added as a percentage of the total dry glaze weight. The percentage determines not just intensity but can change the color completely (iron oxide moves from amber at 2% to deep tenmoku brown-black at 10%). The ranges shown are starting points — test tiles are always required.

Common Colorants at a Glance

Colorant	Color	Typical Range	Notes
Cobalt Carbonate	Blue	0.25–1%	Very potent — start at 0.25%
Red Iron Oxide	Amber → Brown → Red	2–12%	Reduction: celadon at 1–2%
Copper Carbonate	Green / Turquoise	1–5%	Reduction: copper reds
Manganese Dioxide	Purple / Brown	2–8%	Limit to <5% for food ware
Chrome Oxide	Olive Green	0.5–3%	Never near tin glazes

Atmosphere Effects

Firing atmosphere (oxidation vs. reduction) dramatically changes colorant results. Copper carbonate produces teal-green in oxidation but can create stunning copper reds in reduction. Iron oxide produces warm ambers and browns in oxidation but cool celadons and carbon-trap effects in reduction. These ranges apply to oxidation firing; adjust expectations for alternative atmospheres.

lightbulb Quick Tips

check_circle Always do test tiles before committing to a production run — colorant results vary significantly by glaze base chemistry.
check_circle Cobalt is very strong — start at 0.25% and increase in small increments. A little goes a very long way.
check_circle For food-safe ware, use oxides within established safe limits: cobalt <2%, manganese <5%, copper <3%.
check_circle Wear a respirator when weighing colorant powders — metal oxide dusts are a serious inhalation hazard.

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Frequently Asked Questions

How much cobalt carbonate for a medium blue? expand_more

Approximately 0.5% cobalt carbonate on a 1000g batch (5g) gives a clear medium blue in most clear or white glazes. At 0.25% it is a pale blue; at 1% it is a deep blue. Cobalt is the most powerful colorant in ceramics.

Why does iron oxide produce different colors in reduction vs. oxidation? expand_more

In oxidation, iron remains as Fe³⁺ (ferric), producing amber, yellow, and brown. In reduction, Fe³⁺ is converted to Fe²⁺ (ferrous), producing the greens of celadon at 1–2% and the rich blacks/browns of tenmoku at 8–12%.

Are metallic oxides food-safe in glazes? expand_more

When properly fired into a well-formulated glaze, most colorants are food-safe. The concern is with soluble heavy metals that can leach out of under-fired, poorly formulated glazes. Cobalt, iron, and rutile in normal quantities in a fired, non-leaching glaze are generally safe.