Slip Casting

Brongniart's Formula Calculator

Calculate dry material content and water content in a slip using Brongniart's formula.

Updated

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Use 2.6 for mixed clay body slip (default). Pure kaolin: 2.63. Ball clay: 2.58.

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Enter your measurements above and click Calculate.

Brongniart's Formula

Alexandre Brongniart, director of the Sèvres porcelain factory in the 19th century, developed a formula for calculating the dry material content of a clay slip from its specific gravity and volume. It remains one of the most useful tools in slip casting and industrial ceramics today.

The Formula

// Slip to dry content:

dry_content_g = V × (ρ_slip − 1000) × ρ_solids / (ρ_solids − 1)

// Where:

V = volume in litres

ρ_slip = slip density (SG × 1000 g/L)

ρ_solids = density of dry clay (≈2.6 g/cm³)

Two Calculation Modes

Slip SG → Dry Content

Measure your slip with a hydrometer and find out how many grams of dry clay are in a given volume. Useful for production consistency checks.

Dry Weight → Predict SG

Start with a known weight of dry material and a target water volume, and predict the resulting slip SG before mixing. Useful for recipe development.

Solids Density Reference

The solids density (ρ_solids) varies slightly between clay materials. Use 2.6 g/cm³ for most mixed clay body slips. Pure kaolin: 2.63. Ball clay: 2.58. Porcelain slip: typically 2.5–2.65. The default of 2.6 is a reliable approximation for most ceramic applications.

Frequently Asked Questions

What is Brongniart's Formula? expand_more
Brongniart's formula calculates the dry weight of solids in a slip given its specific gravity and the density of the dry materials. It is a fundamental calculation in industrial ceramics for slip quality control.
What solids density should I use? expand_more
For most mixed clay-body slips, use 2.6 g/cm³ — the approximate average density of fired clay minerals. For pure kaolin use 2.63, for ball clay use 2.58, for feldspar use 2.56. Mixed bodies are well-approximated at 2.6.