Tinting Parian Slip with Oxides - test tiles - updated with results April 26

The slip had previously been measured into 100ml containers, two of which were selected for this series of tests. Each was divided equally into five smaller containers, resulting in 20ml of slip per sample.

The focus of this test was to observe the effects of incremental additions of two different oxides: cobalt carbonate and copper carbonate. Cobalt carbonate was added in measured quantities of 0.125%, 0.25%, 0.5%, 1%, and 2% relative to the dry weight of the clay, calculated at 16g per test sample. Copper Carbonate was added in measured quantities of 0.125%, 0.25%, 0.75%, 1.25% and 2.5%. This structured approach aimed to reveal how subtle variations in oxide concentration influence colour development in parian slip.

In practice, measuring such small quantities proved extremely challenging. Even with high-precision scales, achieving exact measurements at these low percentages introduced a margin of error that could affect the reliability of the results. Reflecting on this, future tests would benefit from working with larger sample sizes, reducing the impact of minor inaccuracies and allowing for greater consistency in oxide addition.

The coloured slips were applied to four test tiles: two for cobalt carbonate and two for copper carbonate. For each oxide, one tile is intended for reduction firing and the other for stoneware firing, enabling a direct comparison of how atmosphere influences the final colour outcome. Additionally, half of each tile will be dipped in a transparent glaze, allowing for further comparison between raw and glazed surfaces.

I am particularly interested to see how the different firing conditions and glaze applications will affect the final results. These tests should provide valuable insight into both the behaviour of tinted parian slip and the potential for developing a nuanced, controlled colour palette in future work.

• 

• 

• 

• 

Results after firing

• 

•