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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.
Convert each oxide weight from material analyses to moles by dividing by the oxide molecular weight. Sum contributions from all materials in the batch.
Moles oxide = (weight × oxide%) / (100 × molecular weight)Divide all oxide mole totals by moles of SiO₂ to express the formula on a silica-unity basis. Al₂O₃/SiO₂ ratio indicates glaze durability and melt temperature.
UMF oxide = moles oxide / moles SiO₂Group R₂O (Na₂O, K₂O, Li₂O) and RO (CaO, MgO, ZnO, SrO) fluxes. Their balance affects gloss, melt temperature, and thermal expansion of the fired glaze.
Flux total = Σ R₂O + Σ RO (mole basis)Updated: July 2026
Frit 3124, silica, and kaolin batch yields UMF: SiO₂ 2.8, Al₂O₃ 0.35, CaO 0.45, K₂O 0.12. Al₂O₃/SiO₂ of 0.125 indicates a durable glossy glaze.
Recipe A has MgO 0.38; Recipe B has MgO 0.22. Higher magnesia in A explains stronger matte character and higher melt viscosity at cone 6.
Replace potash feldspar with soda feldspar; recalculate UMF to verify Na₂O/K₂O shift. Adjust silica or kaolin to restore the original Al₂O₃/SiO₂ ratio.
Oxide comparisons must be on a mole basis. 10% CaO by weight is not equivalent to 10% K₂O — convert to UMF before judging balance.
Commercial frits contain B₂O₃ and Li₂O that act as strong fluxes. Omitting frit oxides from analysis produces an incomplete and misleading UMF.
Understanding glaze chemistry starts with the unity molecular formula — the mole ratios of oxides that determine melt, durability, and surface character. Enter raw material percentages and this calculator derives the UMF for analysis and adjustment.