As recently as three years ago, it was thought that measuring the total UV dosage was enough to establish a cure window. By monitoring intensity of the UV exposure over the total time of exposure and integrating that value, it was thought that the UV process had been quantified as thoroughly as possible. As UV users became more sophisticated, they noticed the importance of not only measuring UV but of measuring UV of a certain wavelength. Also, specific wavelengths of light seem to effect a better cure than others on certain pigmented inks and coatings. For example, long wavelengths appear to be more effective with heavily pigmented inks.
Adhesives require both short and long wavelengths to cure properly.
To further complicate the issue, some users believe that the entire UV spectrum plays some role in proper curing. Figures 1-4 demonstrate how different the output spectra of two lamps may be. Now many formulators and end users are discovering that just monitoring the UV dosage within a particular spectrum of interest is not enough. It is equally important, or perhaps more important, to determine how that UV is delivered. In other words, at what intensity was the dosage received.