This is to ensure that the proper shade is achieved in the next dyeing cycle. The analysis is performed with a spectrophotometer. Procedures for performing this analysis are presented in reference 2, along with a computer program which will simplify calculating the required dyestuff additions. Reconstituting the bath. Reconstituting the bath consists of adding back the quantities of water, auxiliary chemicals, and dyestuffs needed for the next dyeing cycle.
Water is added to replace any lost through evaporation or in the product.
Auxiliary chemicals are also added in proportion to the amount of water added. Any auxiliary chemicals that exhaust during dyeing are added to make-up for such exhaustion losses. In general, these quantities can be estimated and do not require exact analysis. Reusing the bath for subsequent processing. The major difference in reusing a dyebath is that the starting temperature is generally higher than that of fresh water.