How Much Thiourea Dioxide Should I Use Instead of Sodium Hydrosulfite?

There is no universal conversion factor.

For polyester reduction clearing, published processes using sodium hydrosulfite commonly fall around 1–5 g/L, depending on process conditions. For example, publicly available polyester procedures report approximately 2–3 g/L sodium hydrosulfite with NaOH at 70–80°C.

A practical Thiourea Dioxide screening matrix could be:

Trial A: Thiourea Dioxide 0.5 g/L, NaOH 1–2 g/L, 70–80°C, 15–20 min

Trial B: Thiourea Dioxide 1.0 g/L, NaOH 1–2 g/L, 70–80°C, 15–20 min

Trial C: Thiourea Dioxide 1.5 g/L, NaOH 1–2 g/L, 70–80°C, 15–20 min

Trial D: Thiourea Dioxide 2.0 g/L, NaOH 1–2 g/L, 70–80°C, 15–20 min

Important: these are screening concentrations, not guaranteed production recipes.