Topic: Spiral ground paperweight with canes

[tropdevin]

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Hi Roger.

I don't know what the Baccarat Dupont UV response would be (I am very doubtful of the value of UV testing, as some of my fellow collectors on this board know...) but a Dupont weight would be made of lead crystal, and feel dense in the hand compared to a Caithness piece.  I have not seen any Dupont canes that look like the ones in your paperweight.

I would go for the 'out of hours' option, maybe with Caithness canes, but perhaps not at Caithness?

Alan

[Roger H]

Hi Alan, done a lot of uv testing lately and have come to the conclusion in some areas of glassworks it is very usefull but in others confusing.  Certainly could not attribute definately via this measure but its useful as an indicator. I have found different uv colours within the caithness range of weights maybe due to change of glass composition over a period of time and also the colours used within the weight seem to vary the reflected uv colour especially when its difficult to shine the light through the clear glass part and it picks up shades from the artwork inside.
      Its interesting what you say about the "caithness canes but made elsewhere" possibility.
   Yes I have found one in a reference book which is a possibility and it could have been the early stages of his delight in spirals.   Thats about as far as I can personaly take it I believe.
          Many thanks Roger.

[tropdevin]

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Hi Roger.  The issues about using UV fluorescence as a tool are many, and complicated.  It does have its uses - for example, the work Kevin Holt has done on distinguishing what period an Ysart paperweight might come from, or when a Perthshire paperweight was made.  But it is not really a diagnostic tool that aids ID. For a start, different people use different lights made for different purposes (mineralogy, philately, security etc), which do not necessarily use the same wavelengths - and the UV response is sensitive to wavelength. Then the detection device - the human eye - is not quantitative, and is quite variable.  What does 'straw' colour, or 'dusky yellow' mean?  Probably different things to different people.

There have been serious academic studies of glass fluorescence by people such as Woldemar Weyl, and one finding was that both the gas composition in the glory hole (which varies depending how far in an item is inserted) and the annealing process affect the UV fluorescence of the finished product.  That means using UV fluorescence for ID is not going to be very successful.

Another problem is that although two paperweights may appear to fluoresce the same way, they can be from very different sources.  Conversely, two paperweights made at the same factory by the same maker at roughly the same time can fluoresce quite differently (I have had this demonstrated to me).   

The analogy I like is one with visible light: we use our eyes to tell whether a tomato is ripe by looking at the colour.  But you cannot extend this to conclude that any green fruit is an unripe tomato, or that any red fruit is a ripe tomato.  Fruit colour has its use in differentiating between specimens of a known fruit, but it is of little or no use for identification of the type of fruit.

Alan

[Roger H]

Mmmmmm, UV reaction is useful but not diagnostically reliable.     Sounds a good conclusion to me.
      Thank you very much for your input, has balanced it up better.
                    Regards Roger.