Firing Effects
The glaze longquan_iron_mashiko_0 with three different firing protocols.
The first firing drops from top temperature to 1750 deg F at 300 deg F an
hour. This rate of temperature
The second firing drops only to 2210 deg F at that rapid rate of 300 deg F an
hour. It then has a one-hour hold,
The third firing has a Two-hour hold on the way up, before maturation, at 2250
deg F, 60 degrees below the
The primary difference between these three firings is that slowing down of the
firing at a temperature
The first firing has no hold, in the second firing, the hold is on the way
down, and in the third,
I have previously noticed that glazes high in mica seem more "melted" with a
hold near maturation.
bowl is ~ 4 inches in diameter.
bowl is ~ 4 inches in diameter.
bowl is ~ 4 inches in diameter.
The third firing is a hot cone 10, perhaps cone 10 and a half.
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
300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F
300 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
150 deg F an hour to 250 deg F
400 deg F an hour to 2050 deg F then a hold of 20 min
120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F
300 deg F an hour to 2210 deg F then a one hour hold at 2210 deg F
80 deg F an hour to 1900 deg F
300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F
300 deg F an hour to 1700 deg F then a Two hour hold at 1700 deg F
300 deg F an hour to 1600 deg F then a Two hour hold at 1600 deg F
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 2250 deg F then a two hour hold at 2250 deg F.
120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F
300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F
300 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
K2O 0.11
Al2O3 0.71
SiO2 4.27
molecular percent Silica 69%
In the first firing, where thickly applied, this glaze is a full gloss, inky
black with silvery-bronze markings.
In the second firing, a thicker application of glaze is required to allow the glossy
black matrix visibility.
In the third firing, with an even thicker glaze application, the bronze
colored crystals almost entirely
The hold before peak temperature in the last firing, is considerably hotter
than the hold after peak temperature
More time at a higher temperature allows more crystal growth. The cones in all
three firings are nearly the same.
drop is an approximation to "dropping like a
stone", yet slow enough that the multiple zones in the kiln can
maintain
nearly the same temperature.
then drops to 1900 deg F at only 80
deg F an hour.
top temperature.
near the top, but not so high that a higher cone
would thereby be reached.
on the way up.
This is an exploration of the effect of such
holds on a oil spot glaze, seen
here:
Image of the glaze longquan_iron_mashiko_0 in Firing 1
inside
outside
Image of the glaze longquan_iron_mashiko_0 in Firing 2
inside
outside
Image of the glaze longquan_iron_mashiko_0 in Firing 3
inside
outside
oxidation firing to cone 10 in an electric kiln
Firing profile 1
Up Fire profile
Down Fire Profile
Firing profile 2
Up Fire profile
Down Fire Profile
Firing profile 3
Up Fire profile
Down Fire Profile
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula longquan_iron_mashiko_0 :
Na2O 0.45
Li2O 0.15
CaO 0.11
MgO 0.18
Fe2O3 0.19
Remarks
Where thinly applied the entire field is
covered in what appears to be etched metallic bronze markings.
The outside of the bowl, with a similar
quantity of glaze as the pot seen in the first firing is now entirely covered
in the
metallic bronze crystals.
cover both inside and outside of the bowl.
The pinholes are the result of the thickness of the glaze application.
in the second firing. It is
therefore unclear if the increased effect seen in the third firing is a result
of the
higher temperature, or the positioning of the hold before rather
than after peak temperature.