Tenmoku glaze on Mugs

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,
then the mask is removed and the open area filled in with a second glaze.

In each case the mug is ~4.5 inches in height.



Image of the pieces

full view

mug with iron_satIron_Z2W_0PAlSi and inlay longquan_n_song_0PLi_redart



full view

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

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 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

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



glaze compositions

Background glazes

Empirical Formula iron_satIron_Z2W_0PAlSi :

K2O        0.20
Na2O        0.39
Li2O        0.29
CaO        0.04
MgO        0.08

Al2O3        0.66
Fe2O3        0.24

SiO2        4.07

molecular percent Silica 68%



Empirical Formula iron_satIron_Z2W_0 :

K2O        0.21
Na2O        0.41
Li2O        0.27
CaO        0.04
MgO        0.07

Al2O3        0.61
Fe2O3        0.23

SiO2        3.81

molecular percent Silica 67%



Inlay Glaze

Empirical Formula longquan_n_song_Z2G_0PLi_redart :

K2O        0.10
Na2O        0.13
Li2O        0.09
CaO        0.49
MgO        0.10
ZnO        0.09

Al2O3        0.48
Fe2O3        0.015

SiO2        3.76

molecular percent Silica 72%

Added:

0.02% Cobalt Carbonate

0.2% Silicon Carbide for local reduction



Remarks

The two glazes, iron_satIron_Z2W_0PAlSi and iron_satIron_Z2W_0, have essentially the same bases,
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.

The smaller increment of alumina and silica in iron_satIron_Z2W_0PAlSi gives a glaze which, if thin, is an opaque metallic bronze,
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.

Carol's Home Page