GoKawiilI have a pen-plotter! It’s great. It’s like having a printer but slow and it breaks more often. I got it on eBay and it came sorta broken and I immediately spent the difference between what I paid and the price of new one fixing it. Now it’s fixed!
My favorite thing to do with the pen plotter is to create things that I wouldn’t be able to create on, say, a printer, or by hand. Sometimes that’s because the medium is different; for example, these gold ink postcards I made of an Iguanodon fossil:
But recently, I’ve gotten excited about using the pen plotter to make holograms.
You could derive hand-drawn holograms from scratch
William Beaty has an amazing page about how to make holograms by hand and it includes intuitive explanations of the optics behind them. You can read this page for an awesome explanation of why hand-drawn holograms work and what makes them so effective.
But instead, I want to show you how you could understand hand-drawn etch-holograms entirely intuitively and de novo, without any prior knowledge of holography, and without any math. It all starts with greasy fingers.
1. Greasing your fingers
I selected a nice extra virgin olive oil for this, but you can substitute for vegetable or coconut, to taste.
It was a truly bizarre experience deliberately smearing my fingers with oil and then touching my phone screen. Try it! Rules are made up!
You’ve probably seen a similar smudge before on your own phone. You get these little “highlights” where the light reflects off a particular part of the smudge. On the right side I’ve drawn a schematic of what’s happening: the light finds a path from the light source to your eye that bounces off somewhere along the ridges left by your fingerprint.
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