leaf

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 1850 deg F then a hold of 2 hr at 1850 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 crystal springs porcelain from Georgies in Portland.

glaze composition

Empirical Formula satIron_ZG_H_5_nn :

K2O        0.10
Na2O       0.48
Li2O       0.25
CaO        0.15
MgO        0.02

Al2O3      0.63
Fe2O3      0.21

SiO2       4.03
P2O5       0.04

molecular percent Silica 68.25%

Empirical Formulae of leaf wash glaze leaf_Z3C:

Na2O       0.55
Li2O       0.45

Al2O3      0.45

SiO2       3.59
P2O5       0.19
TiO2       3.44

molecular percent Silica 41.43%

Empirical Formulae of leaf wash glaze leaf_Z35_1:

K2O        0.72
Na2O       0.21
CaO        0.06
MgO        0.01

Al2O3      1.03

SiO2       7.01
TiO2       7.75

molecular percent Silica 41.9%

A leaf is softened by soaking in water laced with water softener. After the pot is glazed, the leaf is pressed
into the glaze. When the glaze dries, a swatch of plate including the leaf is coated with wax. When the wax
is dry, the leaf is removed and the indentations in the glaze are coated with a very thin layer of an
underfired glaze.

This firing profile differs from that used for previous leaf print firings, in that it has a two-hours hold at 1850 deg F,
replacing a shorter hold at 1750 deg F. The background glaze also differs from that used in more recent leaf print
attempts. Different firing, different background, makes it difficult to determine which processing
change is responsible for the result. I expect both are relevant.

This hold at a higher temperature inhibits the growth of the coppery colored micro-crystalline clusters,
which I so adore in this family of saturated iron glazes. That is seen in the orangey-brown center part of the second plate.

Here are earlier leaf prints, fired with a two hour hold at 1850 deg F
Look particularly at the leaf print on the first bowl. It was this leaf print that incited me to add that hold
at 1850 deg F, and is also the reason that I believe that hold is a contributor to the difference between these and
earlier leaf prints.

The background glaze for the second leaf print is almost twice as thick as that of the first leaf print,
which contributes to the orangey-brown center ring surrounding that leaf print. That thicker background contributes to,
but is not the entire cause of the difference in appearance between these two leaf prints.
The different leaf washes is likely the major cause of the contrast in appearance.