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Iridescence - Describe and quantify
iridescence. It’s often in the eyes
of the beholder. Craig wrote - "Iridescence: (This is what its all about
and the one area where my most costly mistakes have been
made)................Defining good iridescence is a lot like how the
Court system defines pornography. Its hard to describe but I know it
when I see it.............Iridescence is very difficult to photograph
Therefore, the serious collector must seek out other collectors and
attend conventions. I've made some great advances in this area with the
help of other collectors."
Craig made some very good points - possibly the
most important being the emphasis on meeting other collectors and
looking at their glass. But what actually IS iridescence? To start with,
it's one of the main things that distinguishes Carnival from other
glass. Marigold Carnival without its iridescence is a clear piece of
crystal glass.
So, how does Carnival get its iridescence? After
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 (cooled
slowly).
 Harry Northwood's notebooks refer to the
application of iridescence. In the book "Harry Northwood, The Wheeling
years" by Heacock, Measell and Wiggins, there are some extracts from
Northwood's notebooks that refer to the iridizing process. 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."
Finally, let’s look at some more of Craig’s
observations:
(1) Iridescence is a very quality oriented
attribute rather than something quantifiable. Judging its qualities is
probably similar to judging the qualities of any art or anything visual
for that matter. Here we go with the art thing and carnival glass!
Well, I think its true, just like studying
paintings or sculptures, I find that the more examples of iridescence I
review, the better I get.
(2) I've also found, as a beginner that beauty is
definitely in the eye of the beholder. Some collectors like the
"silvery" finish that some amethyst pieces have and some find it
distasteful. I am of course aware that a real electric piece whose
iridescence is well balanced can really take ones heart away and fetch a
premium in the auction market.
And we’ll end with a comment from Nancy:
And if iridescence is a problem, here is my own biggest guide...If you
look and go " WOW," then check the price and go "ZIKES", it's probably
pretty good.
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