White on Black, or Black on White

I'm finally moving toward something more cohesive that uses all the skills I'm pulling together in the studio. It's been a big learning curve of throwing, firing, glazing and decaling. My biggest dilemma lately has been using the richness of black clay in contrast with white. I'm absolutely in love with Cassius Basaltic. It's a temperamental mid-fire clay with manganese which makes it really black. Unfortunately, I'm finding it difficult to dial in the bisque firing so that it doesn't bloat in the final firing at cone 5. I can fire it to cone 4 without bloating, but the clay loses it's sheen and it's blackness and the mid fire Cone 5 commercial glazes don't respond well to this lower temperature. Also, most of my glazes have issues with craters, pinholing on this clay. So to get a very glossy white is a slow process, but my current idea is to stick with a thicker layer of underglaze, and to use a clear glaze that becomes molten at a lower temperature. All that said, I am getting closer to what I want...

This cup still has problems, but it is much closer to my final goal with this work. It is Cassius, wheel thrown, white velvet underglaze, zinc free glaze, fired to Cone 4. The commercial rose decal was fired in a 3rd firing to cone 016.



This cup was made same as above, however after wheel thrown I hand shaped it.


This is a strange little egg vase, which was fired to Cone 5. Some minimal bloating. The glaze on it is commercial Cone 5 Temmoku which gives it s nice black quality. Clear glaze on Cassius softens the color to a lighter brown so I use Temmoku.


Here is a photo I've included to show the difference between Cone 4 and Cone 5 firing of Cassius. The cup closest to the front is fired at the lower temperature. The cup further back, is shinier (that is the natural clay without glaze) and more black. However, there is obvious bloating (the small bumps).


Lastly, I may have a new approach to my final aesthetic goal that also may be safer to make. Sometimes I get paranoid about manganese absorption while throwing Cassius. There's a lot of debate about it. One of my instructors who's been working in pottery over 40 years says that I just shouldn't eat it and I'll be fine. But, she has also suggested an alternative approach that will allow more flexibility in my aesthetic goals, with closely the same results and completely vitreous. Rather than use Cassius, I'm experimenting with a Cone 10 porcelain and a Cone 10 black slip that includes some manganese and cobalt oxide.

Here are some examples of these new test runs. This is unfired greenware of Babu Cone 10 porcelain with a black clay slip. I'll have more glaze quality control on the whites and be able to easily add decaling. I think her suggestion may be the answer for me. But I still will not give up on Cassius.