Topic: Flint Glass. What is it?

[Sklounion]

A few recipes for glass may be found here:
http://www.sharelynx.net/web/cyclopedia/glass.html
Judging by the somewhat archaic use of language, these are old recipes.

Regards,

Marcus

[aa]

But you are wonderful too Adam A :wink:
Glen

Thanks Glen, but are you sure you're not confusing me with this Adam Aaronson:

http://www.nowplayingmag.com/content/view/1629/47/

We hear a lot about identity theft these days, but this takes the biscuit!

 

[Frank]

Illinois Glass co used the term flint in their 1903 catalogue for all clear glass bottles. They often used the term in association - Flint, Green or Amber Glass. Some other colours are also mentioned - Blue, Clear (light green)

Also, c1900 in the US there was the Eastern & Western Flint Bottle Manufacturers (Association)

Cannot find the term in any European catalogues where the distinguishments are more commonly: Crystal, Lead Crystal and Full Lead Crystal.

In Decorative Glass Processes, A L Duthie 1908 New York. Has a chapter describing many types of glass in use throughout US & Europe - not once is the term flint used. However, in the introduction it refers to the fundamental compositions used and here we find flint glass as being made with Sand, Red Lead, Potassium carbonate and Nitre.

Charleston clarifies the use of flint in English Glass. Earliest reference being 1674. Then in 1676 in The Natural History of Oxfordshire "The blackest flints calcined and white crytsalline sand. But then white pebbles from the river Po in Italy which are later suggested to be pyrites. In fact the formulas discussed later state that they do not contain lead but in fact produce BOROSILICATE GLASS. (Needed that for another thread). By 1700 commonly used was litharge (protoxide of lead). Ravenscroft used no lead in his 1674 patent,  which was referred to as Flint and Pebble Glass then "When later he added lead oxide to his batch, the process by which 'flint glass'gradually came to be synonymous with lead-crystal."

So in summary flint is used to decribe clear glass and probably for most of history, clear glas with lead content of one form or another.

Can anyone say if red lead = lead oxide?

[Max]

Adam said:

Thanks Glen, but are you sure you're not confusing me with this Adam Aaronson:

http://www.nowplayingmag.com/content/view/1629/47/

We hear a lot about identity theft these days, but this takes the biscuit!

LOL!  That made me laugh!  Adam-Android-Aaronson!   :lol:  :lol:

Just as an aside, in this technical conversation that's far above my head; Whitefriars call their clear glass items 'Flint'.

[Adam]

I'm getting embarrassed now!  Thank you all, anyway.  My wife, by the way hates the (real) Angel of the North.

Now this flint business.  My piece which Bernard quoted was in reply to some specific question, now forgotten but it doesn't matter.  I may know a thing or two about the practical side of pressing glass but I don't claim any authority on the word "flint".  I thought I did, when I first reappeared on the glass scene about the time this Board began.  What I said then, based on what I had learned when in the industry, to anyone who would listen, was something like this:-

"There seem to be umpteen definitions of the word 'flint' so far as glass is concerned.  In the Stourbridge area it means something which contains no lead.  In the optical glass industry it means something which contains a lot of lead.  In Gateshead (i.e. Sowerby and Davidson) it means colourless as against blue, green etc.  In that case it happened not to contain lead but that is irrelevant because that was all we made.  In Sunderland (i.e. Jobling) it means anything which isn't 'Pyrex'".

I explained the last sentence in Bernard's quote.  I have just remembered that in the bottle industry some of them talked about "white flint" to mean colourless.

I regarded all that as an amusing irrelevance but when I wrote it, first to Angela and then to others everything went quiet.  I later understood why!!

I have first hand knowledge of the Gateshead and Sunderland bits only.   The optical glass bit is text book stuff.  The rest was more or less hearsay.  I did often wonder about the title "Edinburgh and Leith Flint Glass Works" (now Edinburgh Crystal) who are and were, all the time I knew them, distinguished makers of full lead crystal.  I assumed at the time that they had started out making non-lead glass - perhaps a good example of bending the facts to suit the theory!

To sum up, I know what "flint" meant locally half a century ago.  What it meant then and now, world-wide, I haven't a clue!  Anyone quoting me in the future, please include that!

I am so glad that I am only a technical type and not a semanticist or whatever they are called!!

Adam D

[Bernard C]

Thanks, Adam, for putting us right in so eloquent a way.

I will, of course, refrain from that analogy forthwith.   ... and, I always believed Sem an' Tics was a famous Australian tennis doubles partnership.

Bernard C.  

[Frank]

Can anyone say if red lead = lead oxide?

A quick google proved them to be one and the same.

So since about 1700 flint became the preferred term to differentiate the earlier non lead containing English Crystal which used soda or lime instead of lead. As stated by Hadjamach. It was actually Lead Monoxide or Red Lead.

In the US the name was Red Lead and again it was a component of flint glass at least by bottlers.

Flint is chemically different being Quartz Microcrystalline, greyish black in colour and found in chalk. However it is still an alkali and could in theory have been used as it has been commonly known since antiquity.

Collins English dictionary:
Mentions its use as a component of glass and specifically mentions Flint Glass and White Flint as colourless glass other than plate glass - which certainly supports the notion that those types of glass might not contain flint!
AND
Optical flint is ONE type of optical glass that contains lead oxide.


WIKIPEDIA
With respect to glass, the term "flint" derives from the flint nodules found in the chalk deposits of southeast England that were used as a source of high purity silica by George Ravenscroft, circa 1662, to produce a potash lead glass that was the predecessor to English lead crystal.
with the source quoted as "Kurkjian, Charles R. and Prindle, William R. (1998). Perspectives on the History of Glass Composition. Journal of the American Ceramic Society, 81 (4), 795-813."

This confuses the statements by Hadjamach and lead one to ask both of these sources to qualify their source. However, it does at least show exactly how flint had a use in glassmaking.

TRANSLATIONS OF FLINT (In case anyone can provide info from other countries):
Dutch: vuursteen, iets wat zo hard als vuursteen is

French: silex, Ă©clat de silex, pierre Ă  briquet, pierre Ă  feu, allumage, feu

German: n. - Feuerstein, v. - mit einem Feuerstein ausstatten

Greek: n. πυρόλιθος, τσακμακόπετρα v. βάζω πέτρα στον αναπτήρα

Italian: silice, pietrina, pietra focaia

Portuguese: n. - pedra (f) de isqueiro

Russian: кремень, скряга

Spanish: n. - pedernal, piedra de chispa, piedra de lumbre, piedra de mechero/encendedor, v. tr. - abastecer con piedra de lumbre

Swedish: n. - flinta, stift (i tändare) v. - förse med flinta

[mrvaselineglass]

Hello all
Yes, comparing flint vs. soda-lime 'clear' glass is much muddier than the glass!  I have always understood that any glass made prior to 1863 in the US was 'flint' (with lead oxide content).  1863 was the date that Wm. Leighton at Hobbs, Brockunier & Co. invented soda-lime as a cheap alternative to the more expensive lead-based formula.  The lead-based formula persisted for a while, especially with some of the more traditional glass houses, but they could not compete, price-wise, with the glass companies that made soda-lime formulas.  If it has a high-pitched ring when flicked, it is generally considered to have lead in it.  Yes, I know, not a good idea to flick glass and some prefer to just rub a finger across the top rim (works fine for goblets, but not spooners!).  Some of the elegant glass houses continued with lead in their formulas into later years.  
An example:
A few years ago, a chemist's book from Fostoria was sold on eBay.  It went to a private buyer for $500.  This was the book that was always locked in the safe as 'trade secrets'.  In that book, on a page dated 4/2/1928, was the following formula in chemist's handwriting (using chemistry abbreviations from the periodical chart of elements). It just so happened that one of the pages shown in the auction included a formula for uranium/vaseline/canary glass!   I got permission from the seller to re-use his photo in my book.  I then had Frank Fenton and Jim Measell help me to decipher that page.  This was for one batch of metal.  The page indicated it was from Pot #8, and it was labeled '305' at the top center of the page.  
SAND: 3000 LB.
POTASH: 1825 LB.
LEAD OXIDE: 1630 LB. (labled as red lead)
NITRATE: 240 LB.
TITANIUM COMPOUND 280 LB.
CERIUM COMPOUND 300 LB.
CADMIUM (300 LISTED, THEN CROSSED OUT WITH 'NONE' WRITTEN ABOVE IT - PROBABLY INDICATED THAT IT WAS TRIED BUT LEFT OUT)
URANIUM OXIDE: 100 LB.

comments were listed below the formula: "RESULT: BEST YELLOW YET.  STILL HAS SLIGHT GREENISH FLUORESCENCE.  NOT SO GOOD WHEN MADE INTO A CUP"

The percentage of uranium oxide as compared to the entire formula is 1,35%, which is about what usually goes into the making of uranium/vaseline/canary glass (1 - 2% of total batch weight).  The percentage of lead?  22% for the entire batch.

I found the inclusion of that much lead in the formula to be just as big a surprise as finding the formula in the first place!

Dave

[Frank]

SUMMATION

Flint was used as a source af silica dioxide and used as an alkali for glassmaking. (It is likely to be shown in more modern recipes as SiO2 or Silicon Dioxide or just Quartz).

It appears to have been largely displaced by Lead Oxide and other alkalis.

The word flint glass was then adopted as a replacement for the term Crystal Glass c1700 but in more recent times glass made with lead has again become commonly referred to as Crystal.

It has been widely used in US and UK to refer to colourless glass and in particular with bottlemaking.

-----------------------------------------

It is interesting the way that a word with a specific meaning gets adapted, presumably for marketting purposes to become almost meaningless (effectively).

[Bernard C]

Checking my reference material, Sowerby, Davidson, Jobling and Bagley all used the term "flint" around the 1930s to '60s to describe standard uncoloured glass, i.e. except special glass such as Jobling's Pyrex and Davidson's equivalent, Silbo.   In this context, "flint" is not at all confusing or ambiguous.

Bagley, to a much lesser extent Davidson, and possibly the other two glassworks used the term "white" as an alternative.   At first I found this really confusing, as I think of white as a colour, in a similar way to black, blue, green and red.   I met the term on Tyneside when I first stood at fairs and markets there some years ago.   It was in common use by older dealers and members of the public.   I suspect that it may originate from bottlemaking or, perhaps, glasses for the licensed trade.

Bernard C.