Why calibrate spectrophotometers 

Proper calibration of the spectrophotometer is a key factor in obtaining an accurate and reliable color measurement. Calibration establishes a correspondence between the reference values and those delivered by the instrument. White point calibration is used to compensate for gradual variations in the spectrophotometer. If this white point is no longer correct, all measurements will be distorted. 

Thus, it is essential to ensure that the spectrophotometer used is properly calibrated. 

How to verify calibration of spectrophotometers 

When you receive a spectrophotometer, it is certified and its measurements are reliable. To check its calibration in the coming months/years, follow these steps:   

• Print a sample containing 10/20 grey and colored patches.
• Measure the Lab values of the patches with the certified device and record them in a spreadsheet.
• Keep this print in a safe place to prevent degradation.
• Re-measure the Lab values of the print after several months.
• Study the variations of measurements, if ∆E76 > 5 the device is badly calibrated.

These steps can also be done with previously certified ceramics, whose Lab values are already known.