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Author Topic: Do I not understand? Lead in glass a barrier to fluorescence of uranium opaline?  (Read 1174 times)

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Offline chopin-liszt

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Lead does make the metal softer and easier to manipulate. It doesn't cool quite as rapidly as unleaded glass, giving the maker a little more leeway and time during the hot work, with fewer trips to the glory hole. I believe it is easier to cut too when cold.

Less brittle is a very good way to describe it. As long as it applies to the hot work as well as the cold work.  :)
Cheers, Sue M. (she/her)

‘For every problem there is a solution: neat, plausible and wrong’. H.L.Mencken

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Offline flying free

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Ok, looking for something else and in the book Baguiers et Verres a Boire due XIXeme Siecle (Darnis), there are a number of French uranium glass pieces dating first half 19th.  Most I've checked at a cursory glance are glass without lead.  hmmm. John Ford's 1840 uranium glass must have been remarkable.  I might need to check Pellatt again as I'm sure it mentioned in there that a reduction of something was necessary to stop the glass crizzling.  That might have been to do with uranium in a lead glass batch.


m

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Offline cagney

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  I thought I would put the question to a test with three different uranium based articles. The dolphin candlestick with opal top The Northwood Co. c.1900 non-lead based. The small footed dish  probably Whitefriars c. 1900. Pretty sure lead based. The other candlestick Boston & Sandwich c. 1850s lead based. Pictured are the results using three different light sources. Regular light, long wave UV and short wave UV.

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Offline flying free

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Thanks for taking those photographs Cagney.  I've been mulling over that comment in PK.  I think the fluorescence referred to must mean the yellow/green effect in seen in transparent uranium glass.  And so not an effect seen in opaline glass by eye/daylight.  So an explanation as to why that must have been the reason why there was no experimentation with French uranium opaline glass?  There was nothing different about it so no need to experiment with using uranium in French opalines?  Perhaps an explanation on how to differentiate French opalines from Bohemian opalines if there is a question over identification and the item contained uranium?

 I have a new grey opaline vase c.1870s I think, but Bohemian probably and that is uranium glass.  But not lead glass I don't think.  No indication to the naked eye that  it contains uranium.  I wonder why it does?

 


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Offline cagney

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  In the PK comment the term "slightly opalizing" in conjunction with the dichorimus I think relates to the dark green not allowing much light to pass through.The first photo is of a uranium non-lead bowl c.1930, it has a enclosed openwork [reticulated] flat extended rim and shows this effect quite well I think.
  Precise formula information is extremely hard to come by. Almost all mentions of formula for uranium glass just use the term uranium oxide, no clue as to which one or type. The only documented use of sodium uranate I could find is Heiseys Marigold color c. 1929 mention in an earlier thread www.glassmessages.com/index.php/topic,72470.40html.
  The three remaining photos are the exact lacy compote [princess feather] also mentioned in the thread given. Whatever dichroic effect that can be seen [toes of foot & where stem meets bowl] does not seem to be as "slightly opalized" as as the bowl rim in the first photo. In clear uranium lead glass the dichroic effect does seem to be limited. Very dependent on the type and intensity of the lighting. Red spectrum v.s. blue spectrum I surmise. Pellatt touches on this subject in his 1849 book in relation to his gold topaz. Some snippets from the book; "of a beautiful topaz tint, coloured by uranium, which became richer in hue by diminishing the usual porportion of lead and by increasing the alkali" and "but its facinating peculiarity is lost, indeed, its colourization mostly fades by candlelight".

  I wonder if the grey tint in your vase is the dichroic effect trying to push through the opaline glass and maybe that is the desired effect they wanted.

  note; There is no copyright on photos from Yale.


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Offline flying free

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Thanks for taking those photographs Cagney.  I've been mulling over that comment in PK.  I think the fluorescence referred to must mean the yellow/green effect in seen in transparent uranium glass.  And so not an effect seen in opaline glass by eye/daylight.  So an explanation as to why that must have been the reason why there was no experimentation with French uranium opaline glass?  There was nothing different about it so no need to experiment with using uranium in French opalines?  Perhaps an explanation on how to differentiate French opalines from Bohemian opalines if there is a question over identification and the item contained uranium?

 

 



If I recall correctly there is the point that Baccarat was experimenting with opaline uranium glass. Perhaps this comment in PK is making reference to earlier times when French makers were doing their wonderful opalines and so during that period the point being made is  there was no need/desire to include uranium in the batch.

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Offline cagney

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  I would certainly concede there was no need to add lead to the batch to achieve the desired color. The PK comment seems to rely on the dichroic effect to achieve a goal in opal/uranium. Thus the somewhat negative  attitude toward lead in the batch. What is the goal? More opacity? Lead glass seems to add a more translucent effect, due to greater refracture of light and lessening of the dichroic effect?


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