Monday, 13 October 2014

Post 177 Test tiles from glaze trial no 9

In my last glaze trial I continued my hunt for the 'perfect browns'. I started with a limited number of recipes that I liked from trial no 7 and then made a number of minor changes. Over previous trials the strategy has been  to bracket the inter-relationships between the colourants and then in this trial to test the fine detail. It is a valuable process and after a while you get to more deeply understand the colour impact of any one colourant and then the interactions between them.

 The base glazes I used have been described previously in Post 30 and Post 32. Those posts were over 2 years ago and this trial is testament to the value in finding a useful base and sticking with it.

 In each of the following pictures I have include the tile that was the starting point for the series - usually of 4 variations. The final picture is of a blue series where the same process was followed.
For the browns the colourants are generally combinations of Zinc and Chrome, Red IO and Yellow ochre and Cobalt. I haven't used Manganese. I find with my bases that it produces a muddy colour without much life. There is an interesting difference in the iron oxides. The RIO seems to impart an olive tone at low concentrations through to a yellow brown at higher, while the yellow ochre gives more of the red brown tones. So 4%YO and 1%RIO will be entirely different from 1%YO and 4%RIO.
I just added up all the recipes I've trialled to date and it comes to 622. That's 9 firings and 622 test tiles.I'm just starting to be able to predict an outcome, but always surprised at the result.


Now I've got 18 pots to glaze from the last bisque firing and will be using a number of these new formulations for the trial.

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