Here I show two tenmoku glazes which differ by a small amount, yet fire
noticeably different.
The foreground design for each mug is glazed with longquan_n_song_0PLi_redart.
The design is created by adhering a mask and then applying the main
glaze. After drying, the entire pot is coated in wax,
In each case the mug is ~4.5 inches in height.
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
K2O 0.20
Al2O3 0.66
SiO2 4.07
molecular percent Silica 68%
K2O 0.21
Al2O3 0.61
SiO2 3.81
molecular percent Silica 67%
K2O 0.10
Al2O3 0.48
SiO2 3.76
molecular percent Silica 72%
Added:
0.02% Cobalt Carbonate
0.2% Silicon Carbide for local reduction
The two glazes, iron_satIron_Z2W_0PAlSi and iron_satIron_Z2W_0, have
essentially the same bases,
The smaller increment of alumina and silica in iron_satIron_Z2W_0PAlSi gives a
glaze which, if thin, is an opaque metallic bronze,
then the mask is removed
and the open area filled in with a second glaze.
Image of the pieces
mug with iron_satIron_Z2W_0PAlSi and inlay longquan_n_song_0PLi_redart
mug with glaze iron_satIron_Z2W_0 and inlay longquan_n_song_0PLi_redart
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile
Down Fire Profile
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Background glazes
Empirical Formula iron_satIron_Z2W_0PAlSi :
Na2O 0.39
Li2O 0.29
CaO 0.04
MgO 0.08
Fe2O3 0.24
Empirical Formula iron_satIron_Z2W_0 :
Na2O 0.41
Li2O 0.27
CaO 0.04
MgO 0.07
Fe2O3 0.23
Inlay Glaze
Empirical Formula longquan_n_song_Z2G_0PLi_redart :
Na2O 0.13
Li2O 0.09
CaO 0.49
MgO 0.10
ZnO 0.09
Fe2O3 0.015
Remarks
as seen in the first column components of
their respective Seger formulas. They also both have the same silica:alumina
ratio;
the glaze iron_satIron_Z2W_0PAlSi has a bit more alumina, but also
adds enough additional silica
to retain the same silica:alumina ratio. It
is the different total quantity of alumina and silica that causes the
different final appearance of the two glazes.
but the glaze
iron_satIron_Z2W_0, where thin, is a glossy transparent brown. These
transparent thin sections are most
evident on the handle of the mug with
this glaze.