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Calculate glaze batch weight from unity formula and raw material analysis. Scale recipes to any batch size for consistent studio pottery glazing.
Create kiln firing schedules with ramp rates, hold times, and cone temperatures. Plan bisque and glaze firings for electric and gas pottery kilns.
Calculate clay shrinkage percentage from wet, dry, and fired dimensions. Plan pottery sizes accurately for clay bodies from leather-hard through glaze firing.
Shrinkage is the percent change in length between two stages. Most studio measurements track wet-to-fired or dry-to-fired linear shrinkage on test bars.
Shrinkage (%) = ((L_start − L_end) / L_start) × 100Drying shrinkage occurs from wet to bone-dry as physical water leaves. Firing shrinkage occurs from bone-dry to mature temperature as particles vitrify and sinter.
Total shrinkage = drying shrinkage + firing shrinkage (approximate for small values)To make a fired piece of target dimension, divide the desired finished size by (1 − total shrinkage fraction) to find the wet or leather-hard forming size.
Wet size = Fired size / (1 − shrinkage%/100)Updated: July 2026
Stoneware body with 12% total shrinkage needs a wet thrown height of 4 / 0.88 ≈ 4.55 inches. Trim foot when leather-hard accounting for ~2% drying shrinkage remaining.
Jar and lid thrown from the same body at 13% shrinkage: if the wet jar rim is 4.0 inches ID, fired ID ≈ 3.48 inches. Size the lid gallery accordingly at wet stage.
Cut a 10 cm wet bar, measure at wet (10.0 cm), dry (9.2 cm), and cone 6 fired (8.7 cm). Calculator yields 8% drying + 5.4% firing = 13% total linear shrinkage.
If you form work at wet stage, you need total wet-to-fired shrinkage. Dry-to-fired alone underestimates how much larger to throw or build the piece.
Grog bodies shrink less than fine porcelain. Recalculate whenever you change clay supplier, body formula, or firing temperature.
Clay bodies shrink at every drying and firing stage. Measuring wet, bone-dry, and fired dimensions lets you calculate total and stage-specific shrinkage so thrown or handbuilt pieces finish at the intended size.