Updated: Jan 11, 2019
This failed lustre test is a great way to show how inglaze lustre works, half is oxidised and half is reduced.
The copper lustre has picked up the 3d print lines on the cast, this is an unexpected feature that I really like. It's emphasising the traditional lustre on the modern 3d printed cast.
Sometimes I struggle to describe how the process of inglaze lustres work, this test is a good way to show how it works.
The glaze is formulated the same way a low firing earthenware glaze is using oxides and applied to bisqued work, then it is first glaze fired in an electric kiln (oxidisation) after this stage the glaze will look green due to the copper carbonate used, the piece is then glaze fired for a second time in a gas kiln in a reduction firing. It is during this firing and the reduction phase that a chemical reaction takes place and the atmosphere within the kiln causes the oxides in the glaze to turn into a metallic lustre, sometimes with iridescent effects.
I think this glaze test is going to be a really useful tool to help explain to people how the process works, as they can see the transformation that takes place after the reduction firing.