Vat State Measured

Vat Volume L

Measured Redox Potential mV

Target Redox Potential mV

Measured pH

Target pH

Dosing Response Fitted to the vat

Hydrosulfite per 100 mV g/L

Caustic per pH Unit g/L

Indigo in Vat g/L

Hydrosulfite Already in Vat g/L

Hydrosulfite to Add

— kg

Top-up to bring the vat to target redox potential

Dosing Sheet

Hydrosulfite Dose: — g/L
Caustic Dose: — g/L
Caustic to Add: — kg
Redox Deficit: — mV
pH Deficit: —
Hydrosulfite to Indigo Ratio: — ×

The two response coefficients are vat-specific and drift with bath age and carry-over — fit them from your own dosing log rather than assuming. Sodium hydrosulfite is self-heating and releases sulfur dioxide on contact with acid or moisture; this sizes a dose, not a handling procedure.

Indigo Vat Redox & Hydrosulfite Dosing Calculator — free, with the formula and a worked example, at Textile School.