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Amazing Facts

Facts About Glass




Fused
glass is said to have been discovered about 4,000 years ago by Phoenician
sailors who cooked a meal on a beach under the stars. When they moved their
pots the next morning, the sand beneath had turned to glass. Art glass fusing
virtually disappeared when the Romans developed glass blowing, resurfacing in
the 1940s and growing rapidly in the 1990s when the Bullseye Glass company
developed a special line of fusible glass. While there are many different kinds
of glass, the essential elements are still sand and intense heat. ·        
Fused
glass -- also called warm glass and kiln-formed glass -- happens when cut
pieces of art glass are fired in a kiln to 1600o F or more. The glass starts
out as big sheets of art glass (usually 24" x 36") that I cut by hand
with a simple glass cutter. I use my own designs, combining different sizes,
shapes, textures and colors of glass in two to six layers. Some glass is clear,
some is colored transparent, some is colored opaque, some has an iridescent
coating, and some is dichroic glass (see below). When a piece is all put
together, it goes into my kiln on a ceramic shelf and the fusing begins.

·        
FOURTH STATE OF MATTER·        
What makes glass a unique material is that
it's always a liquid -- glass is known as "the fourth state of
matter" because it has no solid or gaseous state. Even though windows and
wine goblets seem to be solid, the glass they're made of is actually a
supercooled liquid whose molecules are moving very, very slowly. As the glass
heats up in the kiln, its liquid nature becomes visible. At about 1450oF, you
can see the edges of the cut glass starting to soften and melt. At 1550oF, most
glass is beginning to actually flow and behaves like syrup (extremely hot
syrup!), and as its temperature continues to rise, you can actually see it
moving in the kiln. ·        
How
hot the kiln gets has a lot to do with how a particular piece of fused glass
looks when it's done. Some of my designs use a "tack fuse" --meaning
the glass gets hot enough for all the cut pieces to fuse into one solid piece
of glass, but the cut pieces still maintain their individual shape and texture.
Most of my Desert Glass pieces are tack fused. Other designs, like the Light on
Water pieces, are fired to higher temperatures so they reach "full
fuse," with the separate pieces losing their angular shape and melting
into a softly controlled puddle. ·        
After
the glass reaches the right temperature for a particular piece, the cooling
process begins. All the glass has to expand and contract at the same rate
(i.e., have the same "coefficient of expansion") so that the cut pieces
will melt together completely and still be stable when the glass cools again.
The glass is cooled very slowly (annealed), and when it's done, the pieces are
hand filed. Some pieces are fired more than once, with new layers and elements
added in between firings.  ·        
DICHROIC GLASS·        
I use dichroic glass in much of my work.
Dichroic (pronounced dye-KRO-ik) means "two colors" (Greek): dichroic
glass reflects one color (i.e., when light bounces off the surface of the
glass) and transmits a different color (i.e., when light passes through the
glass). A third color is usually visible at an angle. Dichroic glass represents
a contribution of the aerospace industry to the art world. (Re-entry tiles on
the space shuttle have dichroic coatings.) The technology is based on thin-film
physics. Dichroic glass is made in a vacuum chamber, where hot glass is coated
with multiple microlayers of metallic oxides (selenium, titanium, manganese and
others) that have been vaporized with an electron gun. The transmitted and reflected
colors in a particular piece of dichroic glass depend on which metallic oxides
were used, and on how many microlayers were applied and in what order. ·        
When
you look at a piece of dichroic glass, you see the reflected color. When you
hold it up and look through it, you see the transmitted color. If the dichroic
coated glass is on an opaque glass background, like the Soul of Blue and Spirit
Places pieces on black glass backgrounds, you only see the reflected color --
but you see it with great intensity. If the dichroic coating is on a clear
glass background, besides being able to see the colors shift when you look
through it, you can look at the sides of the piece and see that there's
actually no color in the glass itself -- it's clear glass. The colors you see
are physics in action -- the result of the microlayers of metallic oxides,
which are colorless themselves, interacting with light.




















   
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