Great experiment but of course glass has some pretty obvious downsides. We tried something similar some years ago using a DVD laser and coated glass. It is extremely reliable and thankfully cheap. The problem is... how do you read it? There's no instructions.
The worst movie ever so see a screen... Contact... should have taught everyone in this business the rules of this.
"The medium is irrelevant if no one can read it"
and
"You have to leave Jodi Foster a key to be able to build a machine"
So, the beauty of metal is that you can etch it clearly at many levels. In fact, it makes an amazing analog media. What you do with the metal is that you calculate the analog image to etch on it. Then using a laser and the scanning head from a laser printer, you can pass the scanner across the metal and print. A4 paper size or a nice 210x210 square is great for this.
What will you print. This is interesting, you'll layer many images on top of one another at different resolutions.
The first image show clearly in mostly pictures that are readable with the human eye which will explain how the second layer can be read. It should be simple enough that the reader can build said machine by hand using simple tools. Or, they should be able to read it by hand by measuring. See, you're explaining binary and a simple table such as ASCII or a 5 bit subset of it. It should also contain a Rosetta stone to allow linguists to decipher the language.
The second layer explains that we're storing information that should last forever and is a history of our world. And it should describe how to read the third layer which is much denser and contains a more advanced machine. But because the materials required to read the machine may not be available, it also describes the method of storage as well as detailing the more advanced character set. It should describe that the card which has all jagged edges is a dictionary containing 10,000 commonly used words and their definitions. But that each layer and card will contain partial dictionaries around their edges at the 3rd layer.
Density wise, We've managed to simulate 6 layers on increasing density and complexity allowing for about 1tb per A4 sheet of 1mm platinum (I'm sure other metals will work, it was just a good starting point) and the layers of course last more or less time based on the frequency and detail of the layer. Of course, I included extensive error detection and correction on more detailed layers. The simulation suggested that we could store for about a million years (no real way to test) and that most data would remain readable.
Oh, and you could build the devices fairly inexpensively.
We've been testing this in 3 different nation's archival departments. It was really funny because when I met the people from the archives at a symposium, I asked why they weren't doing this. They were like "what" and I just blurted out the design while chewing my lunch. I mean, I thought the idea obvious and they had been wasting time on all kinds of silliness like what Microsoft was doing.
People need to watch more bad movies.