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Author Topic: lead glass  (Read 15186 times)

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Offline kazmusic

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lead glass
« on: March 05, 2007, 05:41:31 PM »
Can anyone tell me an easy way to tell lead crystal glass from regular glass?

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Offline David E

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Re: lead glass
« Reply #1 on: March 05, 2007, 06:15:17 PM »
Welcome to GMB.

Weight is one of the first indicators! 8)

Sometimes it has a very, very light grey tinge - barely detectable. I believe 24% is the minimum acceptable quantity to properly qualify it as "lead crystal", but many companies would add much more than this. Not sure what the top limit is, but 35%, perhaps?
David
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Offline David E

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Re: lead glass
« Reply #2 on: March 05, 2007, 06:18:58 PM »
An addendum. 24% is the minimum level, as suggested, and Ivo's book (Glass Fact File A-Z, Miller's) mentions 65% content for glass used as radiation shielding.

Memo to oneself - always consult Ivo's book first. ;D
David
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Offline Adam

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Re: lead glass
« Reply #3 on: March 05, 2007, 09:45:44 PM »
33% always used to be the UK "full lead crystal" norm, with the 24% used on the Continent rather disdainfully called "semi-crystal".  All figures are expressed as the oxide, PbO.

I have seen 92% reported, with a density the same as cast iron.  Specialised optical use, I believe, and I think has a brownish tint - not very attractive no doubt!

Adam D.

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Offline Patrick

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Re: lead glass
« Reply #4 on: March 05, 2007, 11:30:26 PM »
Hi,  Another way to tell is by " pinging it "  ...........  Vases , bowls and drinking glasses have a sustained bell like ring.
 Regards Patrick

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Offline Mike M

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Re: lead glass
« Reply #5 on: March 05, 2007, 11:40:15 PM »
Hi

And also the colour.....

it gets very complicated but in simplist form

lower lead more yellow
higher lead more blue

not unlike the difference between standard artificial light and flourescent

cheers

Mike

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Offline Frank

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Re: lead glass
« Reply #6 on: March 06, 2007, 11:57:42 AM »
'Pinging' a glass will only tell you about its pinginess - due to shape and thickness of the glass.

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Offline Andy

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Re: lead glass
« Reply #7 on: March 06, 2007, 12:18:20 PM »
Being serious this time!
A couple of facts found at random, Lead-oxide glass invented in 1673 by George Ravenscroft,
used the addition of red lead(lead oxide) increased the working life and density of glass.
Main ingredients are 3 parts silica 2 parts red lead and 1 part potash, plus saltpetre, arsenic
and borax.
Lead glass sometimes referred to as flint glass because early example used silicaa derived
from English flints, rather than Venetian pebbles. It has a distinctive Grey tone and is much
heavier than soda glass.

Hope this helps a bit.
Andy :)
"Born to lose, Live to win." Ian (Lemmy) Kilmister Motorhead (1945-????)

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Offline Frank

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Re: lead glass
« Reply #8 on: March 06, 2007, 01:43:22 PM »
Flint is also used as a term for soda glass... so never assume.

Soda glass of fine quality will also ring. Monart which is know for its thunk, also throws up the occasional melodious chime. Again, all such hints are part of the arsenal of the collector, none of them are definitive....

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Offline KevinH

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Re: lead glass
« Reply #9 on: March 06, 2007, 02:51:02 PM »
See also this message from Sept 2004:
http://www.glassmessages.com/index.php/topic,342.0.html

Regarding the Ravenscroft "invention", there are some folk who suggest that the "glass of lead" of those times was "invented" by another person! Also, lead oxide was, apparently, used in glass long before the time of Ravenscroft. It was the amount of lead oxide included that was the crucial factor.

I am fascinated by Mike's comments: "lower lead more yellow; higher lead more blue". I can understand that this may well be true. But, bearing in mind the different colour perceptions of peoples' eyes (or brain), and the fact that women and men generally see colour slighlty differently, how many of us can actually see, or make sense of, the difference in shades of glass with lead oxide? Or is it only in the extremes of "yellow" and "blue" that we could all agree on a difference? Could we be in danger of getting into discussions akin to the "blue tint of Irish glass" as happened in the 1920s :)
KevinH

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