[Steppes] Roman Standards

[uilliacc]

I was referring to the objects pictured with the article-- I don't think 
they were blown...

As to the brittleness of ancient glass-
blown glass becomes brittle when cooled too fast-- in "modern" glass 
blowing they learned to make it more durable by cooling slow in an 
annealing oven.  The cause of the brittleness is linked to locking in 
the less defined more haphazard crystaline structures. Annealing allows 
the glass structure to relax and realign more slowly into a less 
internally stressed crystaline structure.  Kinda like making diamonds or 
making quartz**

blowing glass is popular for making containers-- whether it's into a 
mold or not--  this particular object isn't meant to contain anything...

as to working or grinding glass
lower temp lump glass tends to be soft rather than brittle---higher 
levels of flux are used to lower the melting point--

glass can also be poured or pressed into a mold, or worked like beads - 
the result would be solid (more survivable than blown glass)--  if 
semi-round it could easily be hand worked into a sphere-- not much 
overworking there (besides heating/cooling of the glass is the problem 
resulting in brittleness)-- also dropping viscous glass into a tempering 
fluid (oil) slowing its cooling rate produces strong well structured 
glass in spheric drops much like making shot-- again if it's mostly 
round to begin with not much "grinding" required-- more like sanding.  I 
based my suggestion on the pictures of the actual object it does not 
appear to be hollow. when in doubt K.I.S.S. is usually right.  you get 
green with copper carbonate, but any copper presence in glass making 
process would likely lean it towards green

**by the way as an undergraduate we spent a summer building a glass 
blowing workshop from scratch, the annealing oven was the one part that 
we couldn't get right-- washing machine  timers and  oven elements 
didn't work, well but the glory hole and melting furnace worked fine 
many fine shapes were blown, few survived the cool down...

in addition to glasswork (sandblast etched, foiled, leaded and grouted 
stain glass), there's several years practical experience in glaze 
formation, kiln building and maintenance(a wood fired, raku and a large 
gas bag wall "walk in" as well as electric), and brazed and welded metal 
work(I'm fascinated with the transformative properties of fire). There 
jewelry work including lapidary.--
I guess I should have learned something in 10 years as a full time 
undergrad... four great instructors at a small regional Ok school... 
priceless...

uillecc


AlKudsi at aol.com wrote:
> I was basing my speculation on the fact that glass blowing into a 
> mold was very popular with the Romans. Although the story was talking 
> about the other standard being made out of chalcedony, that is a 
> relatively easy stone to grind into a sphere (and polish) because it 
> is just hard enough to work (7 on the Mohs scale) but has no clevage 
> points. Most glass of the period, according to some sources, was a bit 
> brittle if overworked, which you'd have to do to grind it, and didn't 
> take on a polished finish easily. Man-created glass at that time was 
> much more likely to be blown into a mold if you wanted it polished. It 
> is true that if it were volcanic glass (obsidian), or glass formed 
> from impact meteorites (such as Moldavite), it would constitute 
> a "star stone" and probably be ground. However, it would probably take 
> an expert to determine just how the glass was worked.
>  
> Yes, glass has a much older tradition than blown glass...faience, used 
> by the Egyptians since about 1500 BC is a form of glass that is then 
> ground, made into a paste with traces of copper to make it blue or 
> blue-green and made into a glaze for pottery by refiring. But the 
> oldest known BLOWN glass, according to most sources, is about 50 BC 
> Phoenicia. Glass can be worked in so many ways, though...as a glaze, 
> as pulled, as blown, as ground, as molded, and as tumbled.
>  
> Sorry, new area of interest: minerals and gemstones, and by default, 
> things such as opal and glass which are technically not minerals, but 
> mineraloids because they do not have a regularly ordered internal 
> structure.
>  
> HL Saqra
> quoting some from the Smithsonian book: _Rock and Gem: The Definitive 
> Guide to Rocks, Minerals, Gems, and Fossils_, as well as some research 
> in my pottery sources.