Topic: Help needed please.... Black Glass question.

[obscurities]

I have a technical question for those of you with a knowledge of the chemistry of glass colors.   I was told at one point that "black" glass is always actually amethyst in color. Much of it that I have seen actually is.....  I am wondering a couple of things.
1) Is this true? If so why?
2) What is the additive that will color glass black? Is there more than one?

Thanks, Craig

[Anne]

Craig, we talked about this a while back, the earlier topic is here: http://www.glassmessages.com/index.php/topic,10322.0.html although it doesn't fully answer your questions it might add a bit more for you.

[Paul S.]

I know nothing of the chemistry of glass  -  but am aware of the Hyalith glass that Ivo has referred us to.    When searchng Hyalith, a description is given of a glass which has the appearance of 'agate'.    Did this limit the use of black glass, because it could only result in an agate look (which perhaps not everyone wanted) or am I mis-interpreting whole thing.
During the 1930s Bagley’s introduced a black glass known as jettique, which continued in production until after 1945.    This particular type of glass was/is completely opaque.    Was this truly black?

[Lustrousstone]

I understood Hyalith to be opaque true black or red and that Lythalin was the agatey one.

Bagley Jettique is not truly opaque and is actually purple/amethyst. Occasionally black is brown or green

[Paul S.]

note what you say.......however, have a look here, and let us know please what you think.

www.stylendesign.co.uk/guidepages/ehtom.html

if you search Hyalith, it re-directs you to 'imitation stone'

[Anne]

And the entry on that link for Hyalith under imitation stone states:

( Hyalith - A deep red or black agate like glass...

which is what Christine was saying, Paul.

whereas the other one is given as:

Lithyalin - A marbled opaque glass, typically red

so Hyalith for pure black would be correct.

Photo example of a Hyalith beaker here:
http://www.flickr.com/photos/8435962@N06/3276858311 and a bit more about Hyalith and Lithyalin in this article on Bohemian Glassware (by Loreen Neville & Michael Svoboda)  here: http://www.rovinginsight.org/library/index.php?content=business-article-001&bohemian-glassware-long-history-of-exellence

[Lustrousstone]

I think agate is used incorrectly here in connection with Hyalith, although it was an imitation stone (hyalos being Greek for glass and lithos being Greek for stone).

Lithyalin was originally Hyalith stained so that it resembled stones such as agate.

[Paul S.]

Anne - my apologies if I have confused you, not intended I can assure you (but certainly thick I am at times).     I was simply taking Ivo's reference to the word Hyalith.    If you then search Hyalith on the link I gave, it re-directs you to imitation stone - and then proceeds to liken Hyalith to Agate (in either black or red).    Agate, as we all know, is not a uniform colour, and is a mixture of banded colours, which may be predominantly in one direction, but not necessarily so.   My original thought had been that possibly this 'non-uniform mixture of shades/colours had perhaps been a reason why Hyalith had a limited use or appeal.    Traditionally, perhaps there was always a higher demand for glass with a uniform colour, whatever that may have been rather than a motley collection of varying shades.   Your statement that  "so Hyalith for pure black would be correct"  -  is really a contradition in terms, and is not true of an 'agate type appearance', which is not pure black or red (or pure any colour).    There would be no point in using the word agate unless there was some reason for doing so, and in a uniform pure colour there is no need.  Over to you  

    

[Lustrousstone]

I think agate is used incorrectly here in connection with Hyalith,

[Anne]

When I was making jewellery many years back, the pure black stone was black agate and the ones with swirls, streaks and blobs in were defined by variant names such as banded agate or snowflake etc...  so I've always understood black agate to be a plain black stone...  but I do think it's one of those areas where different folks use different names and confusion reigns! Perhaps it should have been better described as obsidian like rather than agate like.