Sodium hexametaphosphate is used as a water softener in dyeing or post-processing, which can capture calcium ions and magnesium ions from the insoluble calcium soap, magnesium soap or calcium dye and magnesium dye precipitates that have been formed, and re-dissolve the precipitate. Chemicalbook In other words, introducing sodium hexametaphosphate into the solution can regenerate sodium soap, and even when calcium soap or magnesium soap has been formed, the clot of calcium soap or magnesium soap will disappear. Similarly, sodium hexametaphosphate can regenerate dyes.