About Tatooine….

Despite the title, I would not be blogging about Star Wars or light sabers… I am actually going to share a bit about tattoos. (If you are a Star Wars fan, pinterest users have posted awesome Star Wars tattoos!)

Earlier this week, one of my friends shared this link about the longevity of watercolour tattoos, and that gave me ink-spiration for this post. While searching online for information, I realised that there are actually quite a few articles about the science behind tattoos. This information ranges from how our body’s immune system contributes to making tattoos permanent, to the chemicals that contribute to the different tattoo ink colours, to appreciating fluid dynamics of the inking process, as well as the effect of tattoos on the human psyche.

This TED-Ed video explains very nicely why tattoos last so long. Tattoos are made by poking needles (with ink) into the skin, past the other most layers. The body treats every prick of the tattoo needle as a tiny wound, and our white blood cells react the same way as when we get an infection – by gobbling up the ink-vaders. However, because the human body cannot break down the ink particles, these white blood cells remain stuck in the dermis layer of skin. A little bit like how Han Solo got frozen in carbonite. 2500yearoldtattoo

So what’s so special about tattoo ink, and how do people get all those brightly coloured ones? Traditional tattoo ink (think tribal ones) would have gotten their colours from natural sources like copper, ash, graphite, tree bark, and woad. Modern inks are now created by adding insoluble solid pigments to a carrier liquid, and unfortunately lack any form of comprehensive regulation. This means that there is a large variety of chemicals that can be used as pigments – black (iron oxides in the form of magnetite crystals or wustite, carbon), brown (iron oxide in the form of ochre), red (iron oxide in the form of rust, cinnabar, cadmium red), green (chrome oxide, malachite), blue (cobalt blue, lapis lazuli, azurite), violet (quinacridone, carbazole, manganese ammonium pyrophosphate), yellow (chrome yellow, cadmium yellow, curcuma yellow), and white (lead carbonate, barium sulphate, titanium dioxide). While this diversity of chemical in tattoo inks have the potential for interesting science demos, it is scary to note that some of these chemicals are toxic, and inks containing heavy metals may cause burns during an MRI. The silver lining is that there is ongoing research into tattoo inks, so hopefully we would be able to have safe(r) ink for use.

I would like to wrap up this blog post with the following video that shows fluid mechanics, and how the ink between the needles are drawn into the tiny holes created by capillary action. WARNING! Those of you who have an aversion to needles may want to skip this…. From personal experience, these tiny needles are more ticklish than painful.


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