Breaking Colors

The starting point - the glaze acicular-paper which showed a startling contrast of bright yellow and orange with
sharp boundaries between the two colors making the contrast all that much more apparent.

Strong color contrasts are prevalent in underfired glazes as this glaze so clearly is, as shown by the visible
froth of unhealed bubbles.

As acicular-paper has high alkali metals and low silica, I said "Ah, a silica starved alkali matte glaze,"
and added silica, creating the glaze acicular-paper-PSi.

acicular-paper-PSi is less underfired, so the colors are more subdued.

Next is acicular-paper-1-3, which is derived from acicular-paper, but with higher alkali metals and lower alkaline earths.
This glaze exhibits strong colors, yet the browns dominate if the glaze is thickly applied.

Last, derived directly from acicular-paper-1-3 by lowering alumina and silica, is acicular-paper-1-3-Neph.
The dunting crack is entirely the result of the structural flaws of the pot. The pot was trimmed almost to collapse,
which it did during the firing.

Image of the glaze acicular-paper

full view

inside

full view

outside

bowl is ~3 inches in diameter

Image of the glaze acicular-paper-PSi - increased silica

full view

inside

full view

outside

bowl is ~3 inches in diameter

Image of the glaze acicular-paper-1-3 - increased alkali metals

full view

inside

full view

outside

bowl is ~3 inches in diameter

Image of the glaze acicular-paper-1-3-Neph

full view

inside

Bowl is ~6 inches in diameter

Dunting of bowl caused by overtrimming heal of bowl above foot. Bowl is a sixteenth of an inch thick
where the foot departed the bowl.

oxidation firing to cone 10 in an electric kiln

Firing profiles

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 1800 deg F

300 deg F an hour to 2050 deg F

120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F

Down Fire Profile

300 deg F an hour to 1750 deg F then a 50 min hold at 1750 deg F

50 deg F an hour to 1700 deg F then a three hour hold at 1700 deg F

25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F

Clay body is a grolleg porcelain from Tacoma Clay Art Center.

glaze compositions

Empirical Formula acicular-paper :

K2O        0.06
Na2O       0.30
Li2O       0.22
CaO        0.09
MgO        0.06
BaO        0.13
SrO        0.14

Al2O3      0.66
Fe2O3      0.06

SiO2       3.2
P2O5       0.03
TiO2       0.11

molecular percent Silica 63.3%

Empirical Formula acicular-paper-PSi :

K2O        0.07
Na2O       0.27
Li2O       0.23
CaO        0.09
MgO        0.07
BaO        0.13
SrO        0.14

Al2O3      0.67
Fe2O3      0.06

SiO2       3.5
P2O5       0.03
TiO2       0.11

molecular percent Silica 65.4%

Empirical Formula acicular-paper-1-3 :

K2O        0.07
Na2O       0.36
Li2O       0.21
CaO        0.09
MgO        0.11
BaO        0.08
SrO        0.08

Al2O3      0.68
Fe2O3      0.07

SiO2       3.12
P2O5       0.02
TiO2       0.10

molecular percent Silica 62.5%

Empirical Formula acicular-paper-1-3-Neph :

K2O        0.07
Na2O       0.37
Li2O       0.20
CaO        0.09
MgO        0.11
BaO        0.08
SrO        0.08

Al2O3      0.63
Fe2O3      0.07

SiO2       3.04
P2O5       0.02
TiO2       0.10

molecular percent Silica 62.5%

Carol's Home Page