(HEALTH WARNING – This is a geeky printing post)
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At the end of April 2013 we set out to show the effects of UV daylight on various different digital and analogue label printing technologies and for a few selected printers, different finishes as well. It has now been 4 months since we started this test (view the original blog here) and we have our 1st set of comparative results to report.
Unless you have read the 1st blog post, most of what follows will be hard to understand, so if this subject is new to you, please read about the purpose of this experiment and the methodologies we have adopted in the 1st blog post before continuing.
1) – overall colour fading
Our results show that using average figures, yellow has faded the most, followed by Magenta, Cyan and then Black least. Recall that the human eye can see colour differences less than about 2.3, so it is, on average, just about noticeable.
You can download the full data from the original dataset and September 2013 measurements and calculations here .
|average Delta E|
|Median Delta E|
Using Median values, the yellow and cyan swap positions, but still fade the most. However the devil is in the detail as you will see from the individual colour blocks.
2) colour fading of the individual colour blocks on different printing platforms
This is the data we have recorded after 4 months
|per colour||average||printing process||finish|
In order of average delta E colour change on the unfinished samples (ie no lamination or varnish), the most lightfast is EFI Jetrion UV inkjet (1.37), Domino UV inkjet (2.33), Durst UV inkjet (2.58), Xeikon (2.7), HP Indigo (5.35), Epson (8.8) and finally Water based Flexo (13.33).
- As an initial finding, the various UV inkjet and Xeikon dry toner technologies demonstrate good lightfastness even after 1 full summer of daylight exposure with some, but hardly noticeable changes.
- HP Indigo colours fade a little faster, particularly the yellow, and the Epson water based inkjet fades even more and is quite noticeable, apart from the blotchiness described below.
- Water based flexo fades by far the fastest and worst, and is very noticeable.
- Both varnish and lamination finishes accelerate and exacerbate the rate of fading in sunlight for some reason. Both the Xeikon varnished sample and the Epson varnished sample has faded a little more than the unvarnished samples. However, the laminated xeikon samples has faded significantly more.
3) – Epson “blotchiness”
One additional and obvious observation is that the Epson samples have gone very blotchy due to some process relating to sunlight exposure, as it is on both Epson faded samples, but not on the unexposed control samples that have been in a cupboard out of daylight.
4) The comparative picture scans – before and after
On the left hand side we have the original images straight off the printers and on the right hand side we have the latest images all taken in early September 2013. Exactly the same equipment was used to scan each image so they are approximately comparable. You can click each of the images to be taken to the full size image to inspect them at their original size. You can also save them for future reference by right clicking and save as. Flick between each one in a new tab as before and after to see the colour changes.
Based on the current data, we are happy to continue to specify Xeikon printing technology as lightfast, and so recommend digital labelling over water based flexography for outdoor applications. It remains to be seen if laminating prints significantly reduces the fading, but we will report back on this in 6 months time when we next take measurements. In the meantime, the print samples are back in my conservatory soaking up the daylight!
Please leave your comments and suggestions below. If you are Labelexpo next week then I’d be pleased to chat with anyone about the results. Please drop me an email.