Glaze Recipe Scaler

How pottery glaze recipes work:

Glaze recipes are written as percentages that add up to 100. Each ingredient is a percentage of the total dry weight. To make a batch, you decide how much total dry glaze you need, then multiply each ingredient’s percentage by that total.

The formula:

Ingredient weight (g) = Total batch weight (g) × (Ingredient % / 100)

How much dry glaze do you need?

A general rule for dipping glaze: 100 grams of dry glaze (mixed with water to dipping consistency) covers approximately 1 square foot of bisqueware. For brushing glazes, you need about 50% more because multiple coats are required.

Worked example:

A classic cone 6 satin glaze recipe:

• Nepheline syenite: 40%
• Silica (flint): 25%
• Whiting (calcium carbonate): 15%
• EPK kaolin: 10%
• Talc: 10%

You need 500g total for a small batch:

• Nepheline syenite: 500 × 0.40 = 200g
• Silica: 500 × 0.25 = 125g
• Whiting: 500 × 0.15 = 75g
• EPK kaolin: 500 × 0.10 = 50g
• Talc: 500 × 0.10 = 50g

Water ratio: Add 40–50% of the dry weight in water. For 500g dry: add 200–250g water. Mix thoroughly, sieve through an 80-mesh screen, and test the consistency. It should coat your finger and drip smoothly, roughly like single cream.

Colorant additions are calculated OUTSIDE the 100% base:

• Cobalt carbonate (blue): 0.5–2% of dry weight
• Iron oxide (brown/amber): 2–10%
• Copper carbonate (green): 1–5%
• Rutile (tan/brown): 3–8%

For 500g dry glaze with 2% cobalt: 500 × 0.02 = 10g cobalt added on top of the 500g base.

Paste the whole recipe. The box below takes a full recipe, one ingredient per line, in whatever form you copied it from a book or a forum post. All of these parse:

Nepheline syenite 40
Silica (flint)  25
Whiting: 15
EPK kaolin - 10
Talc 10
Cobalt carbonate 2

Ingredient names can contain anything; the number at the end of the line is the percentage. Colorants written past 100 are handled correctly, so if your lines add up to 102 the calculator will tell you the base is 100 and the extra 2 is an addition on top, which is how glaze recipes are conventionally written.

Tips:

• Weigh ingredients on a digital scale accurate to 0.1g
• Always sieve twice for consistent results
• Label every bucket with the recipe name, cone, and date
• Test new recipes on test tiles before glazing finished work

Wear a respirator when weighing dry materials. This is not a formality. Silica and kaolin are the bulk of most glazes, and inhaled crystalline silica dust causes silicosis, which is irreversible. An N95 is the minimum and a P100 half-mask is better. Weigh in a still corner rather than under a fan, wipe surfaces damp instead of sweeping them, and keep the dry powders bagged when you are not using them.

Several common colorants deserve their own caution: cobalt, copper, chrome, manganese and especially barium carbonate are toxic in quantity. Wash your hands before you eat, keep glaze materials out of the kitchen, and do not use a food scale for both jobs.