A few people have asked how we get our images directly onto metal with the metal showing through behind it, and the answer is Dye Sublimation printing. While we’re not going to reveal all of our secrets, anyone in the industry will be able to tell you the basics (and if you want even more detail there’s a good article on Wikipedia which we’ve cribbed a bit for this blog post…), so here’s a crash course.
We don’t use white dye sublimation ink, so the underlying surface shows through the picture. In the case of wood prints, this means you can clearly see the colour, grain and knots in the wood; for metal it means you see the metal, making it an ideal process for metallic pictures such as cars or machinery. Anywhere you would see white ‘paper’ in a normal print, you see the underlying material instead.
The “dye” part refers to the ink, which is technically a ‘dye’ rather than a ‘pigment’ – inkjet printer inks are generally ‘pigments’ which are somewhat less colour fast than ‘dyes’ but also cheaper.
The “sublimation” part – as any GSCE Chemistry student should be able to tell you – refers to anything that goes straight from being a solid to a gas, without the more usual liquid stage in between.
Essentially we print our images as a ‘mirror image’ onto a piece of special paper using dye sublimation inks, and then transfer it onto the prepared surface using high heat and very high pressure. The heat turns the ink directly into a gas, but because of the high pressure and the special coating on whatever we’re printing, it doesn’t simply escape. Instead, it can only transfer onto the surface we want to print. Once the transfer is complete, after anything from 45 seconds to two minutes, we cool the printed surface and the image is visible in the correct orientation. The crucial difference from standard printing is that we’ve now created a bond between the dye and the substrate at a molecular level, and the only thing that will break that bond is high heat, so getting the print wet won’t affect it (although in the case of metal, the substrate can still corrode if it gets too damp).
We like to drill and finish any preparatory holes (for things like clock mechanisms) before we print, so all that is left to do is to apply a protective coating (usually of a clear gloss lacquer) and attach extras like hooks or clock movements. Then we wrap the finished product carefully – clock hands are protected using offcuts from old garden hosepipe, another example of recycling old products – and pack it in recycled packaging to either be sold on shop shelves, or posted out to customers.
It’s worth pointing out at this stage one of the pitfalls of dye sublimation printing – which is that if the print fails, or has too many blemishes, we can’t go back for another go, so we have to take our time over the preparation and printing to get it right first time every time. We don’t waste our few ‘fails’ though, we keep them and use the unprinted side for testing new images and products. We can often ‘bake out’ more basic images in an oven, but we prefer not to do this and just use the reverse!