Glass Identification - Post here for all ID requests > Glass
lead glass
oldglassman:
Hi ,
I have just been re reading this interresting thread and thought that this article may be of interrest to those who have commented here on the subject of lead glass development in England , (scroll down to read full article)
http://www.academia.edu/7121691/Late_17th-Century_Crystal_Glass_An_Analytical_Investigation_Dungworth_and_Brain_
I am told by Colin Brain that more publications are in the pipeline but not yet available for public viewing.
cheers ,
Peter
rabugheida:
The way that i can be fairly sure that the glass is crystal is because of the work that was done on it
I believe that the addition of the lead greatly increases the time one can work on a piece
so if there are intricate cuts it is most probably crystal
anyone?
sph@ngw:
--- Quote from: Patrick 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
--- End quote ---
I have to disagree.
Our new World First glass, non toxic, totally lead free, has a wonderful ring if you "ping it"!
The shape of teh glass bowl also counts for much of the ring-sonority.
The only real way is a chemical analysis using professional techniques to analyse a tiny sample.
sph@ngw:
None so queer as folk. The recognised inventor of lead crystal glass stemware is George Ravenscroft, a (GR)s proved by Dr David Watts, who analysed several Ravenscroft glasses, and found that he gradually added more and more lead until around 35%! there is a chart showing this somewhere in the Glass Circle records
he was NOT the first to add lead to glass, to soften the batch and make it easier to use.
GR was financed by the Worshipful Company of Glass Sellers Co of London who paid for two chairs of makers in Henley on Thames, easy to ship to London, according to my copy of Hartshorne's "Old English Glasses" p 240.
His patent is dated 16th may 1674 (Andy please note) but he probably had made it a year earlier in 1673! The glass Sellers were establish in 1664 so celebrated 350 years in 2014!
Even the Portland Vase overlay (Roman 1st century) has a very small amount of lead that allows easier cameo carving!
sph@ngw:
--- Quote from: rabugheida on January 07, 2018, 12:26:54 PM ---The way that i can be fairly sure that the glass is crystal is because of the work that was done on it
I believe that the addition of the lead greatly increases the time one can work on a piece
so if there are intricate cuts it is most probably crystal
anyone?
--- End quote ---
"work on the piece", in fact means working hot glass for up to 3 minutes, without it going solid on you. Soda lime glass goes solid after about 1 min 10 secs!
The cutting is usually only done on lead glass as it is softer to cut, and to "brush polish" or more recently "acid polish"!
Also lead crystal has the refractive index of over 2.45 so it sparkles like a diamond when cut and polished well Just wanted to clear that up.
Mod: Edited to lift the response out of the quote.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version