It's a question that's only been asked maybe once or twice, but it's a good question. Can a clear tape stuck on top of a direct thermal label protect it from UV, rain and other outdoor elements? In theory I would have said yes it would protect it from rain, dirt and abrasion but not from the hot ultraviolet and infrared exposure of the sun. Of course this meant some testing was to be done.
The Test
On the 2nd of May I printed a label on a Brother QL-560 I happen to have on my desk (any brand direct thermal label will most likely have the same effect). I also have a roll of clear polyester that in my drawer which was perfect for this test. I stuck the DT label on a smooth corner of our building that gets the morning and midday sun, then the clear polyester over the bottom half of the label. What happened over three weeks was rather interesting.
The Results
The whole label seemed to get slightly darker from the original white. The top half's exposure to rain, wind, and unfiltered sunlight reduced the darkness of the print down to about 60% of the original black. There are a couple of extra-faded lines where rain ran down over the label; it even peeled slightly in a few places such as above the "y" and below the "a". The bottom half stayed intact. No fading, no peeling, just slightly darker overall.
The Conclusion
If you want a direct thermal label to last longer than usual, especially if it's going to be exposed to outdoor elements, place a clear label such as a vinyl or polyester over the top of it. I wouldn't recommend using sellotape or clear packing/parcel tape as these could not only distort the visibility of the label, but also be really tricky to get the right size and apply it with no creases. If the label is going to be in a harsher environment or you need it to last a very long time with no change, choose a thermal transfer option as these are designed for this purpose. If you have any other questions for your labelling needs, please contact us on 01202 681311.
Update
Today is June the 29th. It's wet and cold. The last few weeks has seen cold winds, heavy showers, burning sunshine, and high humidities. You couldn't ask for a more extreme environment for a direct thermal label. Take a look at the photo below. The outdoor elements have given this label a pummeling. The top uncovered half of the label is completely faded and starting to flake away. The covered lower half is starting to fade and the water is making its way into the paper and adhesive. I don't think it will be long until this label falls on the floor. Remember: if you need a label to last a long time, you need thermal transfer.
