Will it fade?
Its taken some effort to get prepared, but we are excited to announce the commencement of a major long term comparative trial of the lightfastness of different digital and flexo label printing technologies. The results will take some time, but we believe this will become a definitive study on the lightfastness of all the major digital label printing technologies, plus flexo for comparison.
There is no quality data in the public domain to compare the UV sunlight / daylight lightfastness performance of the major digital labelling technologies, so the question we are seeking to address is “Are there significant differences between the lightfastness of different digital and analogue label printing technologies?”
All of them will fade to a degree, of that we are sure. We know that from the best data we have seen so far which was presented at Label Expo 2011. However this was not as extensive, long or open as this trial is going to be. Since we are curious enough about this issue we are starting to put the data in the public domain from day 1.
To do this experiment we designed an A4 test image (low resolution scans of the control samples below) and arranged to have identical images (apart from the blue printing process name) printed on the following platforms within 2 weeks of each other in April 2013.
- Domino N600i (UV inkjet)
- Durst Tau 330 (UV inkjet)
- EFI Jetrion (UV inkjet)
- Epson Surepress L-4033A (water based inkjet )+ varnished sample
- Flexo (water based inks)
- HP Indigo (liquid electrophotography)
- Xeikon 3300 (dry toner electrophotography) + varnished sample + laminated sample
All 7 were printed with no over varnishing or lamination as the principal samples on the standard semi gloss paper label stock that the manufacturer would use for routine work. However in addition to the unfinished samples, some were varnished and laminated as well to see if the rate of daylight fading was affected by the finishing by varnish or lamination when compared to the same process print which was unvarnished/unlaminated. All were stored out of daylight until the initial measurement.
We measured each of the 100% C M Y K spot colour patches on every one of the 10 samples, 5 times each using a calibrated Xrite Pro 2 spectrophotometer in LAB space and recorded the data in a spreadsheet with an average of the 5 measurements taken as the benchmark. This is 600 individual l/a/b measurements.
We also scanned each image as a 600 dpi jpg file for visual comparative purposes on a Samsung SCX3205 A4 flatbed scanner.
We will shortly be publishing the high resolution images and the base data set of LAB measurements on this blog. [UPDATE 13 May 2013 – the high resolution scans and LAB data are now hosted here.]
Long term daylight exposure test
All 10 A4 sheets were mounted on a flat board and will be exposed to UK daylight for the next 1-2 years or so in a south facing window for maximum daylight exposure. Periodically we will repeat the LAB measurements and post them on this blog, as well as rescan 600 DPI JPG images using identical equipment and conditions and post them here.
We will then calculate the colour difference for each sample from the initial reading for each of the 4 colours using an industry standard colour science measurement of ΔE (CIE76 method from wikipedia). The bigger the ΔE number over time, the more the colour patch has faded.
Using (initial measurements) and (future measurements once faded) we will be able to see which printing technology fades most, and if varnish or lamination makes a significant difference.
These are low resolution images of the control prints (not to be exposed) to show what we are starting off with.
Comments or suggestions on the trial most welcome – please Disqus below!