The Effect on a Glaze of a trace of Chrome

I show here the effect of adding ~0.02% chrome oxide to five glazes.

Previously, I'd added 0.02% chrome oxide to a white matte glaze, to have it turn translucent and grey.
The change in color isn't surprising, because grey is a possible chrome color, the change in texture was unexpected.

I decided upon a quick and dirty investigation of the effect of chrome on matte glazes. I added a
small bit of chrome oxide to each of five matte glazes.

The glazes chosen were recently tested, and I used the remains from those tests. The result is qualatative,
because measuring 0.02g is difficult, and the quantity of glaze to which the chrome oxide was added is approximate.

I divided 0.05g of chrome oxide into five segments, and added one segment to ~50 g of each glaze.

With that small addition of chrome oxide each of these glaze is pitted. Those pits range from slight pinholes
to giant frothy unhealed bubbles. Additionally each of these glazes is somewhat glossier.

Each of these glazes had a greater range of colors with the addition of the chrome oxide.

Each piece is a small bowl ~3.5 inches in diameter.



Image of the pieces

Preceding the image of the glaze with the addition of chrome oxide, is an image of the glaze in its original form.



full view

bowl with glaze faux-tsabar-harris-yellow-Z2R

full view

bowl with glaze faux-tsabar-harris-yellow-Z2R + 0.02% chrome oxide



full view

bowl with glaze ru_P_tsabar_PMg

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inside of bowl with glaze ru_P_tsabar_PMg + 0.02% chrome oxide

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outside of bowl with glaze ru_P_tsabar_PMg + 0.02% chrome oxide



full view

bowl with glaze ru_Z2Q

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bowl with glaze ru_Z2Q + 0.02% chrome oxide



full view

bowl with glaze tsabar-celadon-PAl-PMg-Z2Q

full view

bowl with glaze tsabar-celadon-PAl-PMg-Z2Q + 0.02% chrome oxide



full view

bowl with glaze tsabar-celadon-PAl-Z2Q

full view

bowl with glaze tsabar-celadon-PAl-Z2Q + 0.02% chrome oxide



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

Empirical Formula faux-tsabar-harris-yellow-Z2R :

K2O        0.20
Na2O        0.20
CaO        0.41
MgO        0.06
ZnO        0.13

Al2O3        0.6
Fe2O3        0.02

SiO2        3
SnO2        0.05

molecular percent Silica 64.3%

0.5% copper carbonate

0.5% Silicon Carbide for local reduction



Empirical Formula ru_P_tsabar_PMg :

K2O        0.16
Na2O        0.07
CaO        0.59
MgO        0.16
ZnO        0.02

Al2O3        0.5
Fe2O3        0.02

SiO2        2.54
P2O5        0.01

molecular percent Silica 62.2%

Added:

0.5% Silicon Carbide for local reduction



Empirical Formula ru_Z2Q :

K2O        0.15
Na2O        0.08
CaO        0.51
MgO        0.26

Al2O3        0.56
Fe2O3        0.02

SiO2        2.64
P2O5        0.02

molecular percent Silica 62%

Added:

0.3% Silicon Carbide added for local reduction



Empirical Formula tsabar-celadon-PAl-PMg-Z2Q :

K2O        0.22
Na2O        0.07
CaO        0.54
MgO        0.11
ZnO        0.06

Al2O3        0.61
Fe2O3        0.01

SiO2        2.88

molecular percent Silica 64%

Added:

0.5% Silicon Carbide added for local reduction



Empirical Formula tsabar-celadon-PAl-Z2Q :

K2O        0.22
Na2O        0.06
CaO        0.64
MgO        0.02
ZnO        0.06

Al2O3        0.61
Fe2O3        0.01

SiO2        2.86

molecular percent Silica 63.7%

Added:

0.5% Silicon Carbide added for local reduction



Empirical Formula tsabar-harris-celedon-PAl :

K2O        0.21
Na2O        0.07
CaO        0.65
MgO        0.01
ZnO        0.06

Al2O3        0.56
Fe2O3        0.01

SiO2        2.77

molecular percent Silica 63.6%

Added:

0.5% Silicon Carbide added for local reduction



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