Bruce Girrell on mon 1 jan 01
Greetings and happy new year!
When I posted my review of the Intel QX3, I said that I would discuss
my photographs further. The pictures are posted at the Strictly
Unofficial Clayart Web Site -
http://www.clayart.fsnet.co.uk/BGirrell.html
Each photo was taken through the QX3 using the software that came with
the microscope. I used supplemental lighting from a Dolan-Jenner Model
A-200 illuminator. This is a commercial microscopy illuminator that
has an intense light source (think slide projector bulb) that can be
focused on a small area through two adjustable fiber optic light
pipes. The QX3 internal light source would have provided enough light
for these photos, but it made a bad reflection of the surface of the
pot that I was working with.
Also, each photo was imported into Photoshop and I applied an
Automatic Levels adjustment and an Unsharp Mask. These two adjustments
substantially improved the image quality.
1) The first photo shows a portion of the Ceramics Monthly cover at
the three magnifications available with the microscope. I wanted some
way to provide everyone with an appreciation of the degree of
magnification provided by the microscope. I figured that a good number
of have access to a Ceramics Monthly magazine, so I chose that.=20
This picture is _not_ presented at full magnification, though. The
image was too large to put on the web page (see image #2). The main
idea of this picture is to show how the three magnifications relate to
a familiar object.
2) The second picture is the middle picture from the three presented
in image#1. Magnification is about 60x. This image is shown full sized
as it would appear on your screen if you were using the microscope. If
you imagine blowing the first image up so that the middle picture
matches this one in size, then you would have the true comparison of
magnifications of the CM cover.
3) This picture shows a portion of one of our pots at 10x. This pot
was glazed with a white crackle glaze and then a coat of Tom Buck's
Red Lustre #8 was applied over that.=20
At the time that this pot was made, we were trying to get some nice
red colors on our pots (before we bought our OxyProbe). This pot was
raku fired, but received no post-fire reduction. We had some success,
but the results were very unreliable. We have since found that the red
is produced by strong reduction in the kiln and develops as the pot
cools. It's amazing to watch the pot turn red before your eyes. RL8
can also produce a khaki green color in oxidation and some of our pots
were both red and green. Sometimes it turned out great, sometimes
awful.
The darkness in the upper left of the photo is due to light fall-off
resulting from curvature of the pot surface. As I mentioned in the
microscope report, it was difficult, especially at 10x, to get the
light pipes close enough to the microscope body so that they could
illuminate the specimen without being blocked by the body of the
microscope.
4) At 60x the formation of the red coloring is more apparent. When
examined with a stereo microscope, it is very evident that this red
color is created in the surface layer of the glaze. In fact, I have
some pictures that show red at the surface with green underneath.=20
I am fascinated by the way in which the red develops. I call the
effect "blood in water". OK, it may be a little gruesome, but to me it
looks as if drops of blood have fallen into flowing water. The red
color is transparent and, until someone can prove otherwise, I believe
it to be a true copper red. RL8 contains ten times as much copper as
is called for in a copper red recipe and in other portions of the pot
you can see tiny copper crystal formation. Where the copper crystals
are visible, the color is no longer the clear red visible in this
photo.
The appearance of flow also intrigues me. What would cause this
phenomenon? Is this actual flow of the glaze as it melts? If so, what
would account for the irregular appearance, as if some sort of
turbulence exists in the flow? It's interesting to note that copper
red glazes are runny. My reds also developed best when the glaze was
on the verge of being overfired. Is it possible that copper red
development somehow depends on flowing?
5) The final image was taken at 200x. Contrast of the original image
was poor, but it cleaned up nicely with Photoshop. There is an error
in the caption of this image. Instead of "In the north-west portion of
the pattern, the red color is seen to lie above the white." the
caption should read "In the north-east..." I really wish you could see
this glaze under the stereo microscope where the depth of the glaze is
so apparent.=20
One thing that actually shows up better in this photo than with the
stereo microscope is the texture of the glaze near the craze lines.
Note how the glaze shrinks inward (toward the pot surface) near the
crazing. This is also evident in the 60x image. Apparently, the cracks
developed before the glaze was done shrinking. Interesting stuff.
Besides the microscope pictures, Janet posted two pictures of our
recent work. Both of these pots are made from our "regular" raku body,
which is the fine raku body from Great Lakes Clay. We are also
experimenting with a "porcelain" raku body which gives cleaner and
more vivid coloring. The orange-brown coloration is from ferric
chloride and the squiggles are horsehair decoration.
Most of you have only seen writings on this list from me, and it would
be easy to think of me as the potter, but our pots are very much a
collaborative effort between Lynne and me. We both create forms. Lynne
excels at decoration while I do better with glaze formulation and
firing. For the horsehair pots, I pull the pots and help manipulate a
turntable while Lynne applies the decoration.=20
6) I like the form of this pot. I call this form a "trumpet vase".
They're hard for me to make because the clay tends to fail as it is
stretched out without any support. They also don't sell well. But I
still like them and make one from time to time. I particularly like
the sort of understated single swatch of horsehair across the orange
background on this particular pot. A big part of horsehair decoration
is restraining yourself from adding too many hairs.
7) The "Broken Pot" shows a new technique that we have been working
on. With multiple firings and horsehair applications we achieve a
negative (white) pattern along with the normal positive (black)
horsehair pattern. This adds depth to the decoration and we find it
attractive. We also like this pot because, between the decoration and
the fact that it is broken, it reminds us of a "found" artifact.
That's all for now. I thank Janet Kaiser for providing the space for
posting these images and for taking the time to actually put them on
the site.
Bruce Girrell
in snowy northern Michigan where Lynne and Sara (our chocolate lab)
say Happy New Year to all as well.
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