I wanted an unusual shot to show off the results from my recent soda can label embossing project, and had some success using this unusual method.
There is a classic physics demonstration, sometimes disguised as a bit of stage magic, in which pieces of glass are made to disappear by immersion in a liquid that has the same refractive index as the glass itself.
I had a Pyrex glass beaker of about the diameter of the spiral I wanted, and I decided to experiment with the oil method for making the beaker invisible to get the shot. It’s a bit messy, and there are some things I’ll do differently next time, but it works. Check out the details, below.
Technique: Invisible Glass Photography
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22 thoughts on “Make: Projects – Invisible Glass Photography”
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Why did you use oil? Surely water has a refractive index closer to that of the glass, and is a lot less messy. Does the oil have some special property that makes it more suitable for this task?
Not so surely, actually. Water has refractive index n=1.33. Pyrex has one of the lowest refractive indices of commonly available glasses at 1.47. Wesson oil, though requiring color correction, had the best combination of refractive index, price, and availability.
Why not glycerine? It’s clear and has n=1.473
A good suggestion, echoed by David Kirschtel, that did not occur to me as I was writing. Baby oil and Karo syrup were also possibilities. All are rather more expensive than corn oil, but if I were to do it again I think I would go ahead and spring for a water-white liquid. Glycerine would be a lot easier to clean up, too.
Way, way back, in a prior century, I inadvertently did this in high school.
I had picked up a surplus 45/90/45° prism (WWII tank periscope part, some 2x2x6″), and wanted to strip the silver off the wide face. I placed the prism into a deep Pyrex dish, and poured on a mixture of sulfuric and hydrochloric acids (“Aqua Regia”), and left it overnight.
To my shock, all I saw in the dish in the morning was the protective backing paint, slumped drunkenly in the dish, as if against a melting ice cube! Fortunately, I poked it with a glass rod, rather than my first impulse of reaching in and grabbing it.
The prism was there, perfectly intact, but perfectly cloaked.
The silver had dissolved, leaving the paint untouched.
You rule. Thanks for going the extra ten miles to get the shot!
I don’t understand. If you remove the oil and the glass beaker, you have no reflection and a lot less mess. Is there a more complicated set up / situation where this technique really pays off?
Actually just answered my own question… might be interesting to see what happens to those handblown glass paperweights with the swirls inside. Thanks for the idea!
Thanks, Kelly. One interesting thing I’ve seen already is what happens when the inner container is not filled with oil, but with something else. Or even left empty. Basically, the container seems to disappear and you’re left with a sort of magical-looking hole, in the shape of the interior volume of the container, in the liquid. The hole by itself looks very strange, and I think a person could get some really cool shots by filling it with weird stuff: gravel, hair, ketchup, the contents of a just-activated chemical light-stick, etc.
Any chance you can post a URL for the original project’s printable spiral that leads to superior scissor cuts when hand-making the tape from drink cans?
Sure. It’s attached to the original project here:
http://makeprojects.com/Project/Soda-Can-Label-Embossing/1921/1
And here’s the direct link for the right-handed cutting template:
http://make-documents.s3.amazonaws.com/lvGBBvDODNYRnNg5.pdf
And for the left-handed cutting template:
http://make-documents.s3.amazonaws.com/wwUmwIrccNIHYqOV.pdf