The meaning of lightfastness

Here’s an example of a common misunderstanding, or mix up in translation, of the meaning of ‘lightfast’ with regards to sticker printing.

As you’ll see, here are two window stickers that will have started life looking identical, but ending up looking very different…The problem is a misunderstanding of print processes, and what they’re capable of producing…or not producing in this case.

The sticker to the left was Screenprinted, using lightfast pantone special green mixed colours. You can see that it retains all of its original vibrancy.

The sticker to the right is actually more recent, using the wrong process for the job in hand. It was produced by another company who should have known better. As you’ll see, the green has actually faded to blue. The yellow element of the mix has quickly faded away. It’s far from the brand colour guidelines!

Blue Wool Scale

Lightfastness of printing ink is measured on a scale known as the Blue Wool Scale. Historically, this was a method of measuring how much dyed fabric faded, over a given time, compared to a sample that was kept away from sunlight.

The scale is used in the same way for printing ink. The test involves exposing a print sample to direct sunlight for a period of three months. Then, it’s compared to a ‘control’ sample that has been hidden from the sun. The amount of fading is given a fade rating on a scale of 0 to 8, 0 denoting any lightfastness at all.

To add to the confusion, different colours in printing ink have different Blue Wool ratings. Of the traditional CYMK, 4 colour process or Full colour process (they’re all names for the same thing) the M or Magenta, followed quickly by Y or Yellow are the first to fade by quite a long measure.

Time and time again we see Window Stickers, Window posters and general Outdoor display print of which the colour has simply faded away, leaving only a drained and faded version of its former glory, bereft of any life and colour, behind.

UV ink

“But my printer said he uses UV ink!”

Maybe he does, but all is not what it seems here either…

UV ink refers to printing ink that is dried using UV light. UV ink isn’t necessarily UV stable, (or lightfast.)

In a nutshell, work produced using the Litho, or Lithographic process just isn’t lightfast. If in any doubt at all, just ask your printer to give you a guarantee of expected lightfastness.

Work produced by the Screenprinting process is very lightfast, and can give years of un-faded colour reproduction.

Some digital print processes can create a lightfast result, but again, best to check!

If in any doubt, call us at Edge Stickers on 01347 823230. We’ll talk you through the best, and most suitable way of producing your work…that won’t fade…