Glaze Settling Rate Calculator

Enter your glaze particle density, fluid viscosity, particle diameter and layer thickness to calculate settling velocity, settling time, and Reynolds number using Stokes law.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Input Particle Density
Enter the density of your glaze's solid particles in g/cm³. Most glaze materials range from 2.3 to 4.5 g/cm³.
2
Specify Fluid Density
Enter the density of the suspending fluid (e.g., water at 1.0 g/cm³ or glaze slop at 1.3–1.6 g/cm³).
3
Provide Particle Diameter
Input the mean particle size in micrometers (µm). Typical glaze grinds are 10–200 µm.
4
Enter Fluid Viscosity
Specify the dynamic viscosity of the glaze fluid in mPa·s (millipascal-seconds). Water is 1 mPa·s; thick slops can be 5–50 mPa·s.
5
Define Glaze Layer Thickness
Enter the depth of the glaze layer in the bucket or on the ware in millimeters. This is used to estimate the full settling time.
6
Review Your Results
Analyze the Settling Velocity and Settling Time to understand your glaze's stability and prevent hard settling issues.

Example Calculation

A ceramic technician wants to predict how quickly a new glaze formulation will settle in its bucket to determine if suspension agents are needed.

Particle Density (g/cm³)

2.6

Fluid Density (g/cm³)

1.0

Particle Diameter (µm)

Fluid Viscosity (mPa·s)

1.0

Glaze Layer Thickness (mm)

Results

7848.0 mm/hr

Tips

Increase Fluid Viscosity for Stability

To reduce settling, increase the glaze fluid's viscosity. Adding suspending agents like bentonite (0.5-2%) or CMC gum (0.1-0.5%) can significantly slow down particle descent without altering the glaze's fired properties.

Optimize Particle Size Distribution

A wider distribution of particle sizes, including finer particles (below 10 µm), helps fill interstitial spaces and create a more stable suspension, reducing the settling rate. However, excessively fine particles can increase drying shrinkage.

Monitor Specific Gravity

A glaze's specific gravity (fluid density) directly impacts settling. Aim for a specific gravity between 1.40 and 1.55 for most dipping glazes. Lower specific gravity indicates a thinner glaze, which can lead to faster settling if not properly suspended.

Managing Glaze Suspension with the Settling Rate Calculator

The Glaze Settling Rate Calculator is a specialized tool for ceramic artists and formulators, designed to predict how quickly solid glaze particles will settle out of suspension. By applying Stokes' Law and inputting factors like particle density, fluid viscosity, and particle size, users can determine the settling velocity and estimated settling time. This insight is critical for preventing hard settling, ensuring glaze homogeneity, and maintaining consistent application quality in ceramic studios in 2025.

Maintaining Glaze Homogeneity for Consistent Results

Maintaining a homogeneous glaze suspension is vital for consistent application and defect-free ceramic production. When glaze particles settle too quickly, the slurry separates, leading to uneven coating, varied fired results, and potential defects like pinholes or crawling. Hard settling, where particles compact into an unmixable mass at the bottom of a bucket, can even render a batch unusable. By understanding and controlling the settling rate, potters can ensure their glazes remain well-mixed, providing uniform coverage and predictable aesthetics across all their pieces.

Applying Stokes' Law to Glaze Settling

The Glaze Settling Rate Calculator employs Stokes' Law to determine the settling velocity of glaze particles. This fundamental principle of fluid dynamics describes the drag force on spherical particles in a viscous fluid.

The primary formula for Settling Velocity (v) is:

v = (2 × g × r^2 × (ρp - ρf)) / (9 × η)

Where:

g is the acceleration due to gravity (9.81 m/s²)
r is the particle radius (half of Particle Diameter) in meters
ρp is the Particle Density in kg/m³
ρf is the Fluid Density in kg/m³
η is the Fluid Viscosity in Pa·s (Pascal-seconds)

This calculation reveals how quickly particles descend through the fluid. The Settling Time is then derived from this velocity and the Glaze Layer Thickness.

💡 The `Fluid Viscosity` is a critical input here. For a detailed breakdown of how your glaze's composition and temperature affect its viscosity, consult our Glaze Viscosity Estimator Calculator.

Predicting Settling for a Standard Glaze Slurry

Consider a ceramic technician preparing a large batch of glaze and needing to understand its settling behavior.

Input Particle Data: The average Particle Density of the dry glaze materials is 2.6 g/cm³, and the Particle Diameter is 50 µm.
Specify Fluid Properties: The glaze is mixed with water, so the Fluid Density is 1.0 g/cm³, and the Fluid Viscosity is 1.0 mPa·s.
Define Glaze Depth: The glaze will be stored in a bucket with a 5 mm layer thickness.

Using Stokes' Law, the calculator first determines the velocity at which these particles will fall. v = (2 * 9.81 m/s² * (25 * 10⁻⁶ m)² * (2600 kg/m³ - 1000 kg/m³)) / (9 * 0.001 Pa·s) This yields a Settling Velocity of 7848.0 mm/hr. This extremely high rate indicates that for a water-based suspension without suspending agents, the particles will settle almost instantly. The calculator would also show a very short Settling Time and a "Very fast — requires suspension agents" subheader, prompting the technician to add flocculants or adjust the recipe.

💡 Particle density, a key input for settling rate, is closely related to your glaze's overall specific gravity. Our Glaze Specific Gravity Calculator can help you measure this property accurately.

Industry Standards for Glaze Suspension and Stability

Within the ceramics industry, maintaining glaze suspension and stability is often guided by practical standards and best practices rather than formal regulations. While there aren't specific governmental mandates for glaze settling rates, manufacturers and professional studios adhere to internal quality control benchmarks to ensure product consistency and prevent costly defects. For instance, a common target for production glazes is that they should not hard settle within a 24-hour period, allowing for easy re-mixing. Many studios also aim for a thixotropic glaze, meaning it thins when stirred but thickens when at rest, which helps keep particles suspended. This property is often achieved by carefully balancing clay content (e.g., 10-20% kaolin or ball clay) and specific deflocculants or flocculants, ensuring that the glaze remains workable yet stable over time.

Frequently Asked Questions

What is glaze settling rate?

Glaze settling rate refers to how quickly solid glaze particles suspended in a liquid (typically water) fall out of suspension and accumulate at the bottom of a container. A high settling rate can lead to 'hard settling,' where the glaze forms a compact, difficult-to-re-mix layer, causing inconsistent application and defects.

How does particle size affect settling?

Particle size significantly affects settling rate; larger, heavier particles settle much faster than smaller, lighter ones, following Stokes' Law. Glazes with a broad range of particle sizes or an abundance of coarse particles are more prone to rapid settling, requiring careful grinding and formulation to maintain stability.

What is hard settling in glazes?

Hard settling is a glaze defect where solid particles compact tightly at the bottom of a bucket, forming a dense layer that is extremely difficult to re-mix into a homogeneous suspension. This often occurs in glazes with inadequate suspending agents or very high specific gravity, leading to inconsistent glaze application and defects.

Why is a low Reynolds number important for Stokes' Law?

A low Reynolds number (typically less than 0.1) is crucial for the accurate application of Stokes' Law because it indicates that fluid flow around the settling particles is laminar, not turbulent. This condition ensures that viscous drag forces dominate over inertial forces, allowing for a precise calculation of settling velocity based on particle and fluid properties.