Pottery Glaze Batch Calculator
Created by: James Porter
Last updated:
Scale a glaze recipe to any batch size by weight, calculate bentonite and water additions, and estimate material cost.
Pottery Glaze Batch Calculator
PotteryScale a glaze recipe up or down by weight, add bentonite and water, and estimate the cost of your mixed batch.
What is a Pottery Glaze Batch Calculator?
A pottery glaze batch calculator scales a glaze recipe to any target batch size while preserving the exact ratio between ingredients, then calculates the bentonite suspension agent, water for mixing, and estimated material cost. Glaze recipes are almost always written as percentages or parts by weight that total a convenient number like 100, but a potter rarely needs exactly that total amount of glaze. This calculator converts a recipe of any size into the precise gram weights needed for a 200 gram test batch, a 2,000 gram studio batch, or a 10,000 gram production batch without changing the chemistry of the glaze.
Scaling matters because glaze chemistry is sensitive to ratio, not absolute quantity. A clear glaze made from 38 percent feldspar, 28 percent silica, 20 percent whiting, and 14 percent kaolin behaves the same whether you mix 200 grams or 20,000 grams, as long as every ingredient is scaled by the same factor. Manually recalculating five or more ingredient weights by hand for every new batch size is tedious and error-prone, especially when working from a recipe written in unfamiliar units or a non-100 total.
Beyond simple scaling, this calculator handles the two additions that turn dry glaze materials into a usable glaze: bentonite for suspension and water for application consistency. Bentonite is a highly plastic secondary clay added at 1 to 2 percent of the dry weight to keep heavier materials like feldspar and whiting from settling into a hard layer at the bottom of the bucket. Water is added at roughly 40 to 60 percent of dry weight to reach a workable consistency for dipping, with the exact amount depending on the glaze materials and your application method.
This tool also estimates the cost of a mixed batch using typical supplier pricing for common ceramic glaze materials, which helps potters budget before committing to a large mix and compare the cost of different recipes for the same finished effect. Knowing that a celadon glaze costs noticeably more per pound than a basic clear glaze, because of specialty fluxes or colorants, helps with both recipe selection and pricing finished pottery accurately.
How the Pottery Glaze Batch Calculator Works
The calculator first sums the amounts you entered for all active ingredients to determine the recipe total, whether you entered percentages that sum to 100 or parts by weight that sum to something else. It then divides your desired batch size by that recipe total to get a single scale factor. Each ingredient weight is the scale factor multiplied by its original amount, which preserves every ratio in the recipe exactly regardless of how the original numbers were written.
Once the scaled dry ingredient weights are known, bentonite is calculated as a percentage of the total dry weight and added on top of the recipe, since bentonite is a suspension additive rather than part of the fired glaze chemistry in most formulations. Water is calculated as a percentage of the dry weight and added to reach the target mixing consistency. The total wet batch weight is the sum of the dry ingredients, bentonite, and water. Material cost is calculated by converting each scaled ingredient from grams to pounds and multiplying by typical per-pound supplier pricing.
Glaze Batch Scaling Formulas
Scale factor = Desired batch size / Sum of entered ingredient amounts
Scaled ingredient weight = Ingredient amount x Scale factor
Bentonite weight = Total dry weight x Bentonite % / 100
Water weight = Total dry weight x Water % / 100
Total wet weight = Dry weight + Bentonite weight + Water weight
Cost = Sum of (ingredient weight in lbs x price per lb)
Example Calculations
Example 1: Test batch of a clear cone 6 glaze
Recipe: 38% Custer Feldspar, 28% Silica, 20% Whiting, 14% EPK Kaolin (totals 100). Desired batch: 200g. Scale factor = 200/100 = 2. Scaled weights: Feldspar 76g, Silica 56g, Whiting 40g, Kaolin 28g. With 2% bentonite: 4g. With 50% water: 100g water. Total wet weight: 304g. This is a typical test batch size for trying a new recipe on several test tiles.
Example 2: Studio production batch of the same recipe
Same recipe, desired batch: 3,000g. Scale factor = 3,000/100 = 30. Scaled weights: Feldspar 1,140g, Silica 840g, Whiting 600g, Kaolin 420g. Bentonite at 2%: 60g. Water at 50%: 1,500g. Total wet weight: 4,560g, which fills roughly a 1-gallon bucket and is enough to dip 30 to 40 mugs depending on application thickness.
Example 3: Recipe entered as parts by weight rather than percentages
Recipe entered as parts: Custer Feldspar 50, Silica 35, Whiting 25, Kaolin 18 (totals 128, not 100). Desired batch: 1,000g. Scale factor = 1,000/128 = 7.8125. Scaled weights: Feldspar 391g, Silica 273g, Whiting 195g, Kaolin 141g. The calculator handles this automatically because it scales relative to whatever total the entered amounts add up to, not a fixed 100.
Common Pottery Applications
- Scale a published recipe found in a book or online from its original test-batch size up to a full studio bucket for production glazing.
- Convert a recipe written in unfamiliar units or an unusual total into the exact gram weights needed on a digital scale.
- Estimate material cost before mixing a large batch to compare the price of a complex glaze recipe against a simpler alternative.
- Plan bentonite and water additions consistently across multiple batches of the same recipe for repeatable application thickness.
- Mix a small test batch from a larger recipe to try a glaze on a handful of test tiles before committing to a full bucket.
- Calculate how much of each raw material to order from a ceramic supplier for a known number of upcoming production batches.
- Cross-check a glaze recipe against the classic recipe reference table to understand how its ratios compare to standard formulations.
Tips for Better Pottery Results
Always weigh dry glaze materials on a scale accurate to at least 1 gram, and wear a particle mask when handling dry materials, since several common glaze ingredients produce fine dust that should not be inhaled. Mix dry materials together first before adding water gradually, which prevents lumps and produces a smoother glaze slurry than adding all the water at once.
Sieve every glaze batch through an 80-mesh screen after mixing, even when every ingredient was pre-sieved by the supplier, since lumps and undissolved material can cause glaze defects like pinholing or specking. Let the mixed glaze rest for at least a few hours, ideally overnight, before the first use, which allows the bentonite to fully hydrate and improves suspension.
Label every batch with the recipe name, mix date, and batch weight so you can reproduce successful results and track how a recipe performs over multiple firings. Keep a small reference sample of dry, unmixed material from each batch in case you need to troubleshoot an unexpected firing result later.
Frequently Asked Questions
How do I scale a glaze recipe up or down?
Add up the parts or percentages of every ingredient in your original recipe to get the recipe total. Divide your desired batch size by that total to get a scale factor, then multiply each ingredient by the scale factor. This calculator does that automatically: enter your recipe as percentages or parts, set the desired batch size, and every ingredient weight is scaled proportionally while keeping the ratios between materials exactly the same.
Should glaze recipes be measured in percentages or parts?
Both work the same way mathematically as long as you are consistent. A percentage recipe assumes the parts add up to 100, while a parts-by-weight recipe can total any number. This calculator normalizes whatever numbers you enter against their own total, so you can use either percentages or arbitrary parts and still get an accurate scaled batch. Most published glaze recipes use percentages because they are easy to compare across different total batch sizes.
How much bentonite should I add to a glaze recipe?
Most glaze recipes benefit from 1 to 2 percent bentonite calculated on the dry weight of the recipe. Bentonite is a highly plastic clay that keeps glaze materials suspended in the bucket and improves how the unfired glaze layer holds together on the pot before firing. Recipes that already contain a plastic clay like ball clay or kaolin at 10 percent or more may need less additional bentonite, sometimes none at all.
How much water do I add to dry glaze materials?
A typical starting point is 40 to 60 percent water relative to the dry material weight, which usually lands the mixed glaze in the 1.40 to 1.55 specific gravity range suitable for dipping. Brushing glazes are mixed thicker with less water, while spraying glazes need more water for a thinner, sprayable consistency. After mixing, check specific gravity with a hydrometer or a simple cup-and-scale test and adjust water in small increments.
Why do my scaled ingredient weights not match common supplier bag sizes?
Scaled glaze ingredients rarely land on round numbers because the math follows the recipe ratio exactly, not commercial packaging sizes. For small test batches, round each ingredient to the nearest gram on a digital scale, which introduces negligible error. For larger production batches, round to the nearest 5 or 10 grams. The ratios between materials matter far more than rounding individual ingredient weights for a test or studio batch.
What is a reasonable glaze batch size for testing a new recipe?
Test batches of 100 to 200 grams dry weight are standard for evaluating a new glaze recipe on a handful of test tiles before committing to a larger mix. This uses a small amount of material, keeps costs low, and still provides enough mixed glaze to dip several tiles or small test pieces. Once a test batch fires successfully, scale the same recipe up to 1,000 to 2,000 grams for studio use.
How much does a typical glaze batch cost to mix?
Cost depends heavily on which materials are in the recipe. Basic feldspar, silica, and whiting glazes cost roughly 50 to 80 cents per pound of dry material, while glazes with specialty fluxes like lithium carbonate, frits, or commercial colorant stains can run several dollars per pound. This calculator estimates total batch cost using typical per-pound supplier pricing for each ingredient so you can budget before mixing a large batch.
Sources and References
- Hamer, Frank and Janet. The Potter's Dictionary of Materials and Techniques, 5th Edition. A&C Black, 2004.
- Hopper, Robin. The Ceramic Spectrum, 2nd Edition. Krause Publications, 2001.
- Cooper, Emmanuel. The Potter's Book of Glaze Recipes, 3rd Edition. University of Pennsylvania Press, 2015.
- Digitalfire Corporation. "Glaze Recipe Calculation and Material Substitution." Digitalfire Reference Library, 2023.