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This is an example of a highly fluid glaze melt that has pooled in the bottom of a bowl. While it may be decorative, this effect comes at a cost. The melt fluidity is often a product of high KNaO - so not surprisingly it is crazing like mad! This crazing weakens the piece, much, much more than you might think. when glaze are thick like this the crazing becomes cracks, they go right down through that thick layer at the bottom of this bowl. And they want to continue right down into the body - and will do so at the first opportunity (e.g. sudden temperature change, a bump). Also, fluid glazes like this are much more likely to leach (because they lack SiO2 and Al2O3). That is crystallization in the middle, who knows how chemically stable that is? Yes, these are commercial glazes having a seal that suggests they are somehow immune to leaching, but multiple different layers are interacting here, there is no possible way to predict the resistance to leaching.
Glossary |
Melt Fluidity
Ceramic glazes melt and flow according to their chemistry, particle size and mineralogy. Observing and measuring the nature and amount of flow is important in understanding them. |
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