Was the Formula for True Black Glass Lost?
December 26, 2018 10:58 AM   Subscribe

I read this tantalizing tidbit on wikipedia: "Formulas for different colors of glass are closely guarded. The recipe for a true black glass was lost during World War I, and modern black glass held to sunlight is a deep purple. Examples of true black glass are circulating in jewelry pieces made to commemorate the funeral of Queen Victoria." Unfortunately, it's totally unsourced, and my research hasn't turned up any extra information. Did true black glass ever exist? Do you know anything about the chemistry of glass?
posted by stoneweaver to Science & Nature (7 answers total) 16 users marked this as a favorite
BBC's In Our Time did a recent episode called The Science of Glass. While I don't remember black Glass being discussed, the episode goes into what makes glass unique chemically and has quite a bit about what makes different kinds and recepies of glass distinctive, and the way in which for a long time particular kinds of glass were well protected trade secrets. In our time episodes also always link to additional reading that you might find relevant.
posted by Rinku at 11:17 AM on December 26, 2018 [3 favorites]

The Society for Historical Archaeology goes into this a bit. It seems that even in its 19th c heyday, "true black" glass, at least in the pieces they've found, was actually very dark green or amber and thick-walled to prevent light from shining through.

I wonder if this also has to do with particle scattering, but I don't know enough about the chemistry/physics.
posted by basalganglia at 11:28 AM on December 26, 2018 [4 favorites]

I think there's a terminological wrangle here, in that "black glass" meant different things in different contexts, and the formulae used for light-proofing in bottles or visors were different from the ones for glass jewellery.

The black glass buttons associated with the Victorian "mourning" period are typically "French jet" or "Paris jet", one of the cheaper imitations of genuine jet. There was also an English approximation called Vauxhall Glass.
posted by holgate at 11:45 AM on December 26, 2018 [5 favorites]

I can imagine that for the use of beads, there's also the possibility of using obsidian, the volcanic glass. If you really want to get to the bottom of it, contact the Corning Museum of Glass, a great place for glass research (the best I guess).
posted by ouke at 12:58 PM on December 26, 2018 [2 favorites]

Coming at this from a different point of view, I work in a laser lab, and we use colored glass filters to filter very specific wavelengths of light. The color of the filter is determined by its specs - e.g. a 610 nm filter blocks everything in the visible spectrum but red, so it is red in color.

Long story short, long-pass filters for the infra-red region are really, really black in color, and a look at their spec sheet confirms this (e.g. RG1000 passes no light in the visible). So we certainly can make black glass, but how common it is out of a scientific context..... dunno.
posted by neatsocks at 3:30 AM on December 27, 2018 [2 favorites]

Examples of true black glass are circulating in jewelry pieces made to commemorate the funeral of Queen Victoria.

If there's pieces in circulation, it's pretty simple to zap them in an X-Ray Fluorescence spectrometer and find what their chemical composition is; from there (waves hands) it should be possible to reverse-engineer the process, so I find the claim that it's impossible to make any more somewhat suspect.
posted by each day we work at 3:40 AM on December 27, 2018 [1 favorite]

Vitrolite was a kind of opaque glass they don't make anymore. You see it in the façades of streamlined Art Deco buildings, often in black but many colors.
posted by Rash at 3:02 PM on December 27, 2018 [2 favorites]

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