conminied from pape J

Techniques

] produce both crackle celadons and non-
crackle celadons. The translucent quality
of a thick celadon glave is given even mare
depth and interest when itis crackled and
stained. Cracks form in the glaze when the
clay and glaze are formulated to shnnk al
slightly different rates on cooling. Rub-
bing the pot with china ink and removing
it by washing can then stain the crackle
lines. The stained crackle pattern can be
laraze and bold, small amd intmcate or even
double stained. Alternatively, the crackle
oun be unstained and appear as [ish scales
or crushed ice. The crackle celadon preces
are generally smoothly thrown and
rimmed creating large curved areas for
development of the unique crackle pat-
terns. Mon-crackle celadons highlight the
beauty of fine detail such as carving and
banding inthe clay forms. The [luidcelacdom
glaze thins out and lightens over sharp
edees and pools and darkens in bellows.
Banding can be cutor pressed inte the clay
forms on the wheel as in the bowls and
vases. [t can also be spiraled up the form
when throwing as in the teabow!s. Carved
deearahon works best for me in teapots,
cups, containers and bowls, A metal irim-
ming teal is weed to cut a pattern of facets
in the leather hard clay. A toothed metal
comb can also be used to create patterns.
Another technique | have used is to brush
aclay ship pattern ontoa leather hard piece.

Firinga feldspathic plaze containing small
amounts of iran in a high temperulure
reducing atmosphere produces truce
celadons, [tis nol a complecated motion.
The Chinese produced celadens long be-
fore chemical analyses or computers, To
work backwards and (ry toreproduce these

November/December )QOG

TERRY RYALS

ancientceladonsdoes provide a challenge.
However, science 1s amazing, Take some
chemical analyses from archacologecal
specimens, combine with analyses of mexd-
em glaze matenals, mex through a.com pu-
ter and start testing. With ihis as a staring
point, and the help of some modern glaxe
formulas, | have prefuced hundreds of
otladon glare tesis over the years. OF these,
lam currently using about eight to ten,

Celadons are very simple glazes. | limit
my formulas toonly five ingredients: feld-
spar, silica, kaolin, calcium and iron ox-
ide, All impact celadon colour, crackle
and surface. One hall percent iron oxide
creates a light green. One percent gives a
basic green celadon, while two to three
percent produces a dark green. To make a
bloc: green celadon the percentinre of tiara
has to be reduced to almost nothing (ic.
0.002 %) by carefully choosing the glaze
ingredients. (Titamum, a trace clement, i8
present in some glaze ingredients.) Yel-
low or olive green occurs with an oxidined
or partially oxiivedd kiln; something |
doan*tactively pursuc. Slight variations in
green also occur by varying the ratios of
the main fluxes (potassium, sodium and
calcium). Because | make my own clay
bodies and my passicn for crackle glazes
has fected their development, most ol
my celadens crackle when fired. How-
ever, fewer cracks occur in the glue if
fine-grained silica is used in the glace
formula. | have found making mon-crackle
celadon glazes very difficult. Toachievea
non-crackle celadon, the overall quantity
at the fluxes needs to be reduced in the
glace along with ts-
ing more of the fluxes
Sdn, masenesiLnt,
iron and Utanium.
Adding fine-grained
silica helps, as wesulel
adjusting the clay
body used, Glossy
surfaced ccladans ane
most commlnly pro-
duced, | also achieve
a semi-matte surlace
by lowering the
alumina content of
the glaze to tem per-
centor less. This pro-
duces a silica matte
sunace. ] have yet to

find 2 magnesia malic or alumina matte
Celadon as appealing

AS each of the five ingredients ina celaden
glave has several variations, the possi bili
ties for formula development are endless,
There are tests to be conceived and ald
less lo be reexamined, mew clay bodies to
be developed and all the many variables of
lhe kaln environment to be scrutinized,
Throughout these explorations T feel the
connection with and appreciation of those
who went before, those who praciuced
their art without highly technical aides
bul, just perhups, had as many test tiles.

History of Celadons

The Chinese first produced celadons over
two thousand years agound they perfected
them a thousand years later during the
Song Dynasty. To the ancient Chinesc,
ccladons resembled bath bronve and jade:
the twa rinst precious materials known at
that ume. Celadons raised ordinary clay
objects into the world of official patron-
age. While the drive to expenment with
teladons was pushed by the patronage of
the wealthy and powerful, the acstheic
appeal and whiktinan usefulness ensured
its long-term survival, After the Song Dy-
nasty, decoration with cobalt Blue and
other eoleurs gained popularity and celadon
production fell dramatically, Today,
celadonsare still produced in China, Japan
and Korea. [ can often find examples of
celadon wares inimportand antique siores,
some of my favorite places to wander.

Terry Ryals

Potters Guild of Bntish Columbia 7