Density Adjustment
Measurement of sodium hydroxide concentration in wet processing baths relies on hydrometer readings that must be standardized to a reference temperature. This evaluation, termed Baumé Scale Correction, accounts for the thermal expansion of the liquid which alters the apparent density. Accurate concentration values are impossible without this mathematical adjustment because hot liquids expand and appear less dense than they are at room temperature.
Temperature Variable
Cold liquors show a falsely high density, while heated solutions read artificially low on a standard hydrometer. Applying the Baumé Scale Correction normalizes these readings to a baseline of fifteen degrees Celsius. Without this step, an operator might add excess sodium hydroxide to a hot bath, believing it is too weak.
This leads to fabric damage and higher production costs.
Calibration Procedure
Automated systems employ electronic density sensors that calculate the necessary adjustment continuously. When performing Baumé Scale Correction manually, a technician uses a reference chart to find the correction factor for the current temperature of the bath. This value is added to or subtracted from the observed Baumé reading.
The corrected value represents the true strength of the liquor.
Operational Tolerance
Industrial mercerizing requires precise caustic control to ensure uniform mercerization. High bath temperatures of forty degrees Celsius require a Baumé Scale Correction of nearly one full degree. Neglecting this difference causes errors in wet pickup and dye affinity.
