more weird glass
Oct. 3rd, 2008 11:25 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
wombat1138While (still) looking for info about "orange manganese" glass, found an intriguing late 19th-C reference to a type of glass called "astralite" that I've never heard of before. It sounds beautiful, though: "resembling aventurin [i.e., goldstone], but containing crystals of a cuprous compound, which by reflected light exhibits a dichroitic iridescence of dark red and greenish-blue." The recipe starts with a base mixture combining (in relative proportion) silica (80), lead oxide (120), carbonate of soda (72), and anhydrous borax (18) with a secondary mixture of either "scale oxide of copper" (24) and "scale oxide of iron" (1); or of lime (5), "scale oxide of copper" (26), and "scale oxide of iron" (2). (I may have to look up the equivalent modern terminology later.)
Even more intriguingly, the same book's (and several other references' from the same period) description of what they call "aventurin glass" indicates that in addition to copper, the basic goldstone recipe may contain an equal or even greater proportion of iron to copper, which I suppose would make sense in shifting the matrix color to a definite iron-based rust-red to reinforce the color of the copper precipitate, as well as strengthening the conceptual parallelism of "astralite" (copper-ion aqua transmission color + metallic copper reddish reflection color?) to the earlier description of gold-based saphiret glass.
Argh. I feel a faint obligation to update Wikipedia, but perhaps not right now.
Later addenda: it just occurred to me that possibly this "astralite" glass is the same stuff referred to on the eBay boards as "dragon's breath"??? Frex, there's a scientific abstract about creating a "red-blue dichroic glass" by controlling copper nanocrystal size with europium as a stabilizer? though they describe their result as red-reflecting but blue-transmitting, which seems counter to my understanding of "dragon's breath".
OTOH this grainy page describes what sounds like saphiret as "the so-called 'livers' (a glass with brown color in reflected light and blue in transmitted)", so I guess that's consistent after all. And-- ooh!-- this ref has a much more detailed version of what sounds mostly like the above description of "astralite", as obtained by overheating a piece of "copper ruby" glass:
Even more intriguingly, the same book's (and several other references' from the same period) description of what they call "aventurin glass" indicates that in addition to copper, the basic goldstone recipe may contain an equal or even greater proportion of iron to copper, which I suppose would make sense in shifting the matrix color to a definite iron-based rust-red to reinforce the color of the copper precipitate, as well as strengthening the conceptual parallelism of "astralite" (copper-ion aqua transmission color + metallic copper reddish reflection color?) to the earlier description of gold-based saphiret glass.
Argh. I feel a faint obligation to update Wikipedia, but perhaps not right now.
Later addenda: it just occurred to me that possibly this "astralite" glass is the same stuff referred to on the eBay boards as "dragon's breath"??? Frex, there's a scientific abstract about creating a "red-blue dichroic glass" by controlling copper nanocrystal size with europium as a stabilizer? though they describe their result as red-reflecting but blue-transmitting, which seems counter to my understanding of "dragon's breath".
OTOH this grainy page describes what sounds like saphiret as "the so-called 'livers' (a glass with brown color in reflected light and blue in transmitted)", so I guess that's consistent after all. And-- ooh!-- this ref has a much more detailed version of what sounds mostly like the above description of "astralite", as obtained by overheating a piece of "copper ruby" glass:
Instead of a transparent deep red tint, a dense opaque brown turbidity was developed. Under the microscrope, by transmitted light, a light-green transparent ground was observed, studded with dark, deep, brownish-black clouds; by reflected light it appears as a beautiful, clear, red mass, in which clouds of shining reddish-yellow points occur.