| 1. Identify the lamp’s wavelength | Check the lamp specification or measure its spectral output rather than relying only on the lamp type. | ISO 21348 defines UV-A as 315–400 nm. Common UV LED peak wavelengths include 365, 385, and 395 nm. A 405 nm peak is outside the UV-A range in this classification. | Record the peak wavelength and, where available, the emission bandwidth before selecting an ink. |
| 2. Match the ink’s photoinitiator response | Confirm that the ink’s photoinitiator system absorbs light emitted by the curing source. | Photoinitiators have wavelength-dependent absorption. An ink that responds well to one UV spectrum may cure poorly under another, even when the lamp appears bright. | Ask the ink supplier for compatibility with the exact lamp wavelength and run a curing test on the intended press. |
| 3. Consider the source type and spectrum | Compare the spectral output of the installed lamp, not just its nominal technology. | Medium-pressure mercury lamps produce a broad output with multiple spectral lines. UV LED systems generally emit within a narrower wavelength band, with peaks commonly specified by wavelength. | For a lamp change, recheck ink compatibility and validate the full cure process; do not assume the previous settings will transfer. |
| 4. Check irradiance and dose | Measure light intensity at the substrate and account for exposure time. | Radiant exposure (dose) is calculated as irradiance multiplied by exposure time. For example, mW/cm² × seconds gives mJ/cm², when the irradiance is measured over the relevant spectral range. | Use a radiometer suitable for the lamp spectrum and measurement range. Follow the ink maker’s cure guidance rather than relying on a generic dose target. |
| 5. Account for ink film and print design | Evaluate ink-film thickness, pigment loading, opacity, and printed coverage. | Thicker or more opaque deposits can reduce light reaching deeper parts of the ink film. Dark or heavily pigmented inks may need different process conditions from clear or lightly pigmented inks. | Test the most demanding colour and coverage in the job, not only a thin clear or white sample. |
| 6. Check the substrate and press conditions | Consider substrate compatibility, heat sensitivity, line speed, and the distance between lamp and print. | Substrates differ in their response to heat and UV exposure. Changes in line speed or lamp-to-substrate distance can change the exposure delivered to the ink. | Run a representative production trial and inspect adhesion, surface cure, and resistance using methods appropriate to the application. |
| 7. Verify cure with an appropriate test | Use application-specific checks; a dry-looking surface alone does not confirm full cure. | Cure performance can be affected by spectrum, dose, ink formulation, oxygen exposure, and print conditions. No single visual check proves suitability for every end use. | Follow the ink supplier’s test recommendations and confirm required adhesion, rub resistance, and other end-use properties before production. |