All Glossary

Bamboo Glaze

A high temperature reduction glaze made by adding a small amount of iron oxide to a magnesia matte base glaze

Key phrases linking here: bamboo glaze, bamboo matte - Learn more

Details

Usually describes a bamboo colored matte glaze (especially in reduction stoneware). These are normally achieved in a magnesia matte white by adding a small amount of iron (0.5-1%) and some tin oxide opacifier.

Related Information

The bamboo matte on the left is better:

It does not stain and does not craze.

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These mugs are Plainsman H443. The cone 10R dolomite matte bamboo glaze on the left (A) has 3.5% rutile and 10% Zircopax added to our base G2571A dolomite matte. The one on the right (B) has the same addition but in a base having less CaO/MgO and much more KNaO. This gives it a craze-prone calculated thermal expansion of 7.9 (vs 6.7 for ours). B also stains badly (as can be seen from the felt marker residue that could not be removed using lacquer thinner). Why does A stain only slightly? It has an additional 4% Gerstley Borate, a powerful flux that develops the glass surface better (giving a slightly less matte surface).

A tin oxide addition improves the visual character of a cone 10R bamboo

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This is the G2571A base dolomite matte recipe. The specimen on the left adds 4% tin and 1% iron oxide. The one on the right has 4% tin oxide and 0.5% iron oxide.

Dolomite bamboo matte glazed cone 10R mug

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Courtesy of Susan Clarke

Two G2571A Bamboo versions: With iron, rutile-zircopax

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These mugs are Plainsman H450 fired at cone 10R. Both have a black engobe (L3954N) applied to the insides and half way down the outside during leather hard stage (the insides are glazed with Ravenscrag silky matte and G1947U over the black engobe). The bamboo glazes can thus be seen over the black (upper half) and the raw buff body (lower). The bamboo glaze on the left has 1% iron added to the base G2571A recipe. The one on the right has 3.5% powdered rutile and 10% zircopax added.

Reduction glaze gone astray returns to color in an oxidation refire

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Refired to 1950F. The recipe is very flux-heavy (high feldspar) dolomite:spodumene matte, zero silica, 4% tin oxide and less than 1% iron oxide. Sounds like crystallization territory. The plate on the left is the way it normally fired. On the right the way it started firing. The mug on the bottom looked like the plate on the right, but look what happened after refiring at 1950F in oxidation! The tin is likely a catalyst for the crystallization that occurred in the original result. Could be a fragile mechanism. This underscores the need for a period of oxidation at the end of a normal reduction firing.

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