Glaze

Glaze Opacifier Calculator

Calculate how much zircopax, tin oxide, or titanium dioxide to add to a base glaze to achieve slight, moderate, or full opacity.

Updated May 2026

Base Glaze Weight (g)

Weight of your base recipe before adding opacifier.

Opacifier

Target Opacity

Custom Addition % (optional — overrides target)

error

Results

calculate

Enter your measurements above and click Calculate.

How Opacifiers Work

Opacifiers make glazes milky or fully opaque by introducing tiny particles that scatter light. The particles are stable at kiln temperatures and remain suspended in the fired glaze matrix without dissolving into it.

Opacifier Comparison

Material	Slight	Moderate	Opaque	Notes
Zircopax (ZrSiO₄)	5%	10%	15%	Most common, clean white, affordable
Tin Oxide (SnO₂)	3%	5%	8%	Warmer white, more expensive
Titanium Dioxide (TiO₂)	2%	5%	8%	Very powerful, may cause mottling
Superpax (ZrO₂)	3%	7%	12%	Smooth finish, less common

Percentages are by weight of the base glaze batch. Results vary with firing temperature and base glaze chemistry.

Effect on Glaze Properties

Zircopax: Slightly reduces glaze fluidity and COE. Very stable — won't change colour response much.
Tin oxide: Reacts with iron and copper oxides to produce distinctive colours. Historically used for classic majolica whites.
Titanium dioxide: Can cause rutile-like mottling and surface texture. Raises COE slightly. Excellent for breaking glaze colours.

Combining Opacifiers

Some potters combine two opacifiers to achieve full opacity at lower individual additions. For example, 8% Zircopax + 2% Tin Oxide can give full opacity while retaining the warmth of tin without the full cost.

lightbulb Quick Tips

check_circle Always test opacifier additions on a tile first. The same base glaze can respond very differently at different thicknesses — thicker application appears more opaque regardless of the opacifier amount.
check_circle Tin oxide at 2–3% combined with zircopax is a classic recipe for brilliant white majolica. The tin enhances the clean whiteness without needing a full tin-oxide batch.
check_circle Titanium dioxide is extremely powerful — more than 8% in a mid-fire glaze often produces a matte or rough texture rather than opacity. Use it sparingly and test.
check_circle Sieve your final glaze through 100 mesh after adding opacifier — zircopax in particular tends to form clumps that cause speckle rather than uniform opacity.

Related Calculators

opacity

Glaze Batch Calculator

arrow_forward

opacity

Glaze Colorant Calculator

arrow_forward

opacity

Glaze Recipe Scaler

arrow_forward

Frequently Asked Questions

What is the best opacifier for a clean white glaze? expand_more

Zircopax (zirconium silicate) at 10–15% produces a clean, bright white and is the most widely used opacifier. Tin oxide at 5–8% gives a warmer, slightly cream white but costs more. Titanium dioxide is very powerful but can cause mottling above 6%.

How much zircopax do I need for a fully opaque glaze? expand_more

Typically 12–15% by weight of the base glaze. At 5% you get slight opacity, 10% is semi-opaque. Above 20%, the glaze can become too stiff and prone to crawling.

Can I use multiple opacifiers together? expand_more

Yes, some potters combine zircopax with a small amount of tin oxide (e.g. 8% Zircopax + 2% SnO₂) to get full opacity at a lower combined addition, reducing cost.

Does opacifier affect glaze COE? expand_more

Slightly. Zircopax slightly lowers COE, which is usually beneficial. Titanium dioxide raises COE slightly. For most studio work these effects are minor, but important in precision glaze chemistry work.