Use the limits for your specific system
Zinc chloride, potassium chloride, boric acid and organic additives work together. Operating ranges vary by formulation, production load and supplier.
Brightness is only one measure
Evaluate coverage, uniformity, adhesion and passivation performance as well as appearance. Random brightener additions may hide the actual process problem.
Keep a useful bath record
Log analysis results, additions, production load and sample-panel appearance. Trends are more useful than a single measurement.
Technical note: Operating ranges and additive doses depend on the installed chemistry, equipment and production load. Use the supplier data sheet, bath analysis and approved safety procedures.