How Printers Use X-Rite Technology for Press Calibration

Press calibration is the process of bringing a printing press into a defined, known, and stable colour state - a foundation state from which consistent colour reproduction can be reliably achieved. Without calibration, a press's behaviour drifts over time as rollers wear, inks change, and mechanical tolerances shift, making it increasingly difficult to produce consistent colour from job to job. X-Rite technology provides both the measurement instruments and the data management tools that make systematic press calibration practical in production printing environments.

Press calibration for offset lithography involves establishing target values for the primary process variables that affect colour: ink density (the amount of ink on the sheet), tone value increase (dot gain - the difference between the dot size on the plate and the resulting dot size on the paper), and print contrast (the relationship between solid and shadow tone densities). When these three parameters are at their defined target values, the press is in its characterised state - and the ICC profile built for that state will accurately predict the press's colour reproduction. An eXact 2 spectrophotometer measures all three parameters simultaneously - density and spectrophotometric data from a single measurement - giving press technicians the complete picture they need for systematic calibration.

The calibration process begins with measuring the press's current state against a standard calibration target. The calibration target is printed on the standard substrate for the press, and the printed result is measured systematically across the sheet to verify consistency. Density and dot gain values are mapped across the sheet, identifying any zones where the press is printing unevenly - indicating roller pressure variations, ink train inconsistencies, or other mechanical issues that need correction before the calibration targets can be met consistently. This diagnostic measurement phase is where calibration starts, not where it ends.

Setting and Verifying Calibration Targets

Once the press is printing evenly, calibration targets are set for each ink colour. For ISO 12647-2 compliant offset printing, specific target density values and dot gain curves are defined for each ink on each substrate class. The press is adjusted - through ink zone settings, impression cylinder pressure, roller hardness, and ink viscosity - until measurements match the target values. This adjustment process, guided by X-Rite measurement data rather than visual assessment, is more precise and faster than traditional visual calibration approaches.

After calibration targets are achieved, a characterisation target is printed to build the ICC profile that describes the press's colour response in its calibrated state. This target - typically the IT8.7 or ECI2002 standard chart - contains hundreds of colour patches that span the press's CMYK gamut. The printed chart is measured with the eXact 2, and the measurement data is processed by profiling software to build the ICC profile. This profile, combined with the calibration data, creates the complete colour management foundation for the press: accurate ICC profiles for prepress colour conversion, and defined calibration targets for maintaining the press in the state that those profiles describe.

Maintaining Calibration Over Time

Press calibration is not a one-time event - it is an ongoing discipline. Presses drift from their calibration state as rollers wear, ink chemistry changes slightly between batches, and mechanical components gradually shift. Maintaining calibration requires regular calibration checks - measuring a calibration test strip printed at the beginning of each significant production period and comparing the results to the calibration targets - and recalibration when drift is detected.

Regular calibration maintenance is simpler and faster than initial calibration because it involves small adjustments to bring the press back to its target state rather than full from-scratch calibration. Color iQC software supports this maintenance workflow by storing calibration targets, tracking measurement history, and flagging when calibration has drifted beyond acceptable limits. For multi-press environments, centralised calibration management through Color iQC ensures that all presses are maintained to the same standards - critical for operations that need colour to be consistent across multiple presses or when jobs are split between machines.

For printers using the light booth range from Seaga Group, standardised viewing conditions complement instrument-based calibration verification - providing the controlled visual evaluation environment needed when human approval is part of the calibration acceptance process.

Conclusion

X-Rite technology enables systematic, measurement-based press calibration that is more precise, more consistent, and more maintainable than traditional methods. By measuring calibration targets objectively, building accurate ICC profiles from measured press data, and supporting ongoing calibration maintenance through quality management software, X-Rite provides the complete technical foundation for press calibration programs that deliver consistent colour run after run. For Australian printers who take press consistency seriously, X-Rite measurement technology is the starting point for a calibrated, controlled production environment.