Glaze Thickness Calculator
Calculate recommended dip time and number of brush coats to achieve a target glaze thickness based on specific gravity and viscosity.
About this calculator
Glaze deposits onto bisqueware at a rate driven by two things a potter controls directly: how dense the glaze suspension is (specific gravity, measured with a hydrometer) and how thick it flows (viscosity). This calculator starts from a baseline deposit rate of 0.33 mm per second — calibrated for specific gravity 1.0 at medium viscosity — then scales it by your entered specific gravity relative to 1.5 and by a viscosity multiplier (0.7 for thin/runny, 1.0 for medium, 1.5 for thick/gel-like glazes selected from a simple 1-3 dropdown). Dividing your target thickness by that effective deposit rate gives the recommended dip time in seconds; a thicker target lengthens the dip needed, while a denser suspension or a more viscous glaze raise the effective deposit rate and shorten it.
If you're brushing instead of dipping, the calculator separately estimates coats needed by assuming each brushed coat adds about 0.12 mm, rounding up to a whole number of coats. It also estimates glaze quantity per square inch of surface as a simple product of thickness, specific gravity, and an empirical constant, useful for batch-sizing a glaze mix before you commit a whole piece to it. These are empirical approximations from studio practice, not a physical model of glaze rheology — actual deposit rates vary with clay body absorbency, bisque temperature, glaze particle size, and how long the piece has been out of the kiln, so use the dip time as a starting point and adjust based on how your specific glaze and clay body actually behave on a test tile.
Inputs
Results
Recommended Dip Time
2.4 seconds
Brush Coats Needed
7
How to Use This Calculator
- Enter the target glaze thickness in millimeters — 0.5–1.0 mm is standard for most studio glazes.
- Measure the specific gravity of your mixed glaze with a hydrometer and enter it (typically 1.4–1.6 for dipping glazes).
- Select the viscosity level: 1 for thin/runny, 2 for medium, or 3 for thick gel-like glaze.
- Read the recommended dip time in seconds for achieving your target thickness.
- If brush-applying, use the brush coats output to know how many coats to apply.
- Use the glaze per square inch value to estimate total glaze needed for your piece surface area.
How the result changes with Target Thickness
| Target Thickness | Recommended Dip Time | Brush Coats Needed |
|---|---|---|
| 0.4 | 1.2 seconds | 4 |
| 0.6 | 1.8 seconds | 5 |
| 1.2 | 3.6 seconds | 10 |
| 2 | 6.1 seconds | 17 |
What each input means
- Target Thickness
- Desired glaze thickness in millimeters. 0.5-1.0 mm is typical for most glazes; thicker for crawl/texture glazes.
- Specific Gravity
- Glaze specific gravity measured with a hydrometer. 1.4-1.6 is typical for dipping glazes.
- Viscosity
- Glaze viscosity: 1 = Thin (runny, quick dip), 2 = Medium (standard), 3 = Thick (gel-like, slower deposit).
How this is calculated
Worked example, using the default values
- Identify Input ParametersTarget Thickness = 0.8, Specific Gravity = 1.5, Viscosity = 2 = 3 input(s) provided
- Calculate Recommended Dip TimeRecommended Dip Time2.4 = 2.4
- Calculate Brush Coats NeededBrush Coats Needed7 = 7
- Calculate Glaze per sq inGlaze per sq in0.186 = 0.186
- Calculate Deposit RateDeposit Rate0.33 = 0.33
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does specific gravity scale relative to 1.5 instead of the baseline 1.0?
The 0.33 mm/second baseline deposit rate is calibrated at specific gravity 1.0, but the formula scales your entered specific gravity against 1.5 (safeGravity / 1.5), which is the typical mid-range for dipping glazes and the calculator's own default. That means entering a specific gravity of exactly 1.5 at medium viscosity gives you the baseline-adjacent deposit rate, not the raw 0.33 mm/s — it's a deliberate calibration point, not a formula error.
How does the viscosity setting change my dip time?
Viscosity is selected from a 1-3 dropdown that maps to a multiplier: 0.7 for thin/runny glazes, 1.0 for medium, and 1.5 for thick/gel-like glazes. That multiplier is applied directly to the effective deposit rate, so a thick glaze (1.5x) deposits faster and needs a shorter dip time for the same target thickness, while a thin glaze (0.7x) deposits slower and needs a longer dip.
Why does Brush Coats Needed use a completely separate calculation from dip time?
Brushing and dipping are different application methods with different physics, so the calculator doesn't try to convert one to the other. Brush coats simply divides your target thickness by an assumed 0.12 mm per coat and rounds up to a whole number — it ignores specific gravity and viscosity entirely, since those properties matter for how glaze flows off a dipped piece, not for how much a brush deposits per pass.
What is the Glaze per sq in estimate based on?
It's a simple product of your target thickness, specific gravity, and an empirical constant (0.155), giving grams of glaze per square inch of surface. It's meant for rough batch-sizing — multiply it by your piece's surface area to estimate how much mixed glaze to prepare — rather than a precise coverage calculation, since actual coverage also depends on bisque porosity and how much glaze runs off during dipping.
Related Calculators
The questions that sit next to this one — chosen by subject, including calculators filed under a different category.
Glaze Recipe Calculator
Calculate ingredient weights in grams from a total batch weight and percentage breakdown of silica, alumina, flux, and colorant.
Ceramics & PotteryCone Equivalent Calculator
Convert pyrometric cone numbers to temperatures in Fahrenheit and Celsius for oxidation and reduction atmospheres.
Ceramics & PotteryKiln Firing Schedule
Calculate total firing time, peak temperature, and cooling time based on target cone, ramp rate, hold time, and kiln size.
Industrial CoatingDip Coating Calculator
Calculate dip coating film thickness, paint consumption, and drain time for industrial immersion coating processes.
More in Crafts, Hobbies & Games.