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How was Ruby and Mother-of-Pearl glass made?

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Glen:
Thanks for that, Frank.

As I see it - pretty much the same as Carnival Glass then. The only difference being the way in which the metallic salts were applied. Spraying is the method used today, of course.

Quote from "Carnival Glass The Magic and The Mystery" (Thistlewood and Thistlewood)


--- Quote ---Once the glass had been fashioned into its final shape, it was reheated and whilst still hot was sprayed with a liquid solution of various metallic salts. The liquid evaporated leaving a finely ridged, metallic film on the surface of the glass that can split ordinary daylight into the spectrum of colors in a rainbow effect. This iridescence is what distinguishes Carnival Glass from other press moulded, colored glassware. The name used in the factories for the iridescent spray was “dope” - and it was usually mixed in a separate building called the “dope house.” After doping, the hot glass articles were annealed.

Different chemical solutions produced different iridescent effects. Iron (ferric) and tin (stannous) chloride, or a combination of the two, were the most frequently used. Sometimes the glass was sprayed more than once, with varying metallic solutions, giving interesting effects. The temperature of the glass when it was sprayed also had an effect. If it was very hot, the iridescent effect would be matt or satin like. If it was not quite so hot, the effect became shinier.

Harry Northwood’s notebooks refer to the application of iridescence. Northwood wrote; “Ordinary Chloride of Iron as bought at wholesale drug stores costs 3½ cents a lb. ...spray on glass when finished ready for lehr...glass must be fairly hot.” He went on to observe: “Spray on glass very hot for Matt Iridescent and not so hot for Bright Iridescent” going on to mention that a spraying of iron chloride on hot glass, quickly followed by a second spraying with a tin solution “gives beautiful effects.”
--- End quote ---


Glen

Sid:
Hello:

The spraying/coating techniques described by Frank's most interesting extract would provide an irridescent surface but I am not sure that is what Bernard is describing in words.

My understanding is that to make cranberry glass, a button of ruby colored glass is stuck on a blow rod followed by a gather of clear glass.  The glass is then blown and worked to the finish desired shape.  This link shows the technique:

http://www.glass.co.nz/gibruby.htm

I would anticipate that similar techniques would apply to opal linings.

I don't have the reference that Bernard quoted so may be totally offbase.  I think that a picture or two might help focus this discussion to make sure we are all talking about the same thing.  

Sid

Bernard C:
Sid — You are right.   I had not seen that piece about ruby glass before, and that is exactly the effect I was trying to describe.   With the Walsh Mother of Pearl, the opal layer is none too stable, and can start to break up into a tiny crackle effect, particularly on small fancies with heavily worked flared and crimped rims.

I have sorted out three or four examples, and will switch to my black studio* later today for this, but at the moment I am having problems in my white studio with a Webb pale blue rose bowl with citron legs and rim and an impressed Rd lozenge, which also needs the black for the UV shots!   Why do I always buy glass which is so difficult to photograph?

Thanks, Frank and Glen, for the iridizing info.   I saw that being done on the end of a pontil rod in a muffle oven at Okra, and I have it clear in my mind, as I am sure that Walsh did it the same way.

Bernard C.  8)

* "studio" = 2 camping tables, 2 multicoloured Persil non-bio tablet boxes, a sheet of glass, black or white cloth, and a selection of lights.   I always include the boxes into the edges of two or three of a series of photographs so that I can check the colour balance.

Frank:
One benefit of the muffle furnace was that the vapours were safely extracted away from the workers. How did they manage the safety issue when spraying?

Glen:
Carnival Glass wasn't called "Poison Glass" in Scandinavia for nothing.

Nowadays they may use masks and have extractors. Look at the photo at the bottom of this webpage to see stannous chloride spraying in action at the Isle of Wight Studio Glass.

http://www.geocities.com/carni_glass_uk_2000/IofWightShell.html

Glen

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