If a coated product comes off the line with inconsistent performance or heavy haze, there’s a good chance the coating bath concentration drifted unnoticed. A Brix refractometer is one of the simplest, most affordable tools to monitor the sump/bath and mitigate the issue altogether.
What Is a Brix Refractometer?
A Brix refractometer measures dissolved solids in a liquid by detecting how much light bends as it passes through a small sample drop. Originally developed to monitor the sugar content in fruit juices and sugarcane, the same principle applies directly to water-based coatings and emulsions. A quick way to measure the drifting solids content, the whole test can take mere seconds.
Why Coating Baths Drift
Concentration in a coating bath can shift over a production run due to evaporation, dilution, or inconsistent replenishment. Even small changes in solids level affect coat weight, appearance, and dry time. A refractometer lets you catch this change early and before it shows up as a rejection.
Setting Up Your Calibration
Every coating chemistry reads differently, so you’ll need a product-specific calibration table:
- Prepare samples at known concentrations (e.g., 1%, 2%, 3%, 5% solids)
- Record the Brix reading for each
- Use that table as your production reference
Once it’s built, anyone on the line can verify bath concentration in seconds with no lab required.
Silicone Dilution
Refractometry is especially useful when preparing diluted silicone coating baths. A quick Brix check right after mixing confirms you’ve hit your target solids level and catches formulation errors before the bath goes into production.
Things to Remember
- Readings can change with extreme temperature differences
- Each product needs its own calibration curve
- At very low solids (below ~0.5%), gravimetric testing is more reliable
- This is a process control tool, not a replacement for periodic lab verification
A Brix refractometer is a low-cost investment with a real impact to consistency. If you’re running water-based coatings or silicone dilutions, it’s a practical addition to your QC toolkit.
Have questions about process control for your coating application? Contact the ACC Coatings team