In order to find other colors of clay, I mixed sandstone.
The principle is simple: from 3 grounds at my disposal, a black ground (super manga), a red sandstone (MJ of Treigny ) and a clearer sandstone of St Amand (GSAT40), I carry out a mixture by triangle by making vary of 20% the proportion of each ground.
Here is the result:
Finding the 80% MJ 20% super manga mix interesting, I'm holding onto this one.
I specify that it is obviously possible to make this type of mixture with different grounds and in different proportions. It remains for you to see what you get, both in terms of color and the reaction of the clay to this mixture at the time of firing.
To pursue my research into ashes and superimpositions, it seemed important to me to try and develop a glaze known as an " oil drop". This name comes from the kind of drops that appear on the glaze after firing.
Brief explanation of the "oil drop" phenomenon
This effect is achieved in glazes with high iron concentrations. At high temperatures, iron, in the form of Fe2O3, is no longer stable enough and is forced to give up oxygen to form FeO. It is this release of oxygen atoms that causes the bubbles on the surface of the enamel to burst, due to the viscosity of the enamel when the oxygen atoms are released, hence the appearance of the different-coloured "drops". This technique is only possible with oxidizing firing. Oxygen atoms are released before this phase in reductive firing.
Search for an oil drop enamel
I do my initial research pretty broadly around the 48 diagram and get a lot of garbage. However, I keep some samples to work on:
Based on these first results, I select the sample at the bottom right to continue the research. In a second step, I vary the % of iron oxides to observe the impact of it on the glaze:
I select the 6th sample on the picture, which is this one:
The effect obtained is interesting but the enamel does not seem to melt homogeneously. Therefore, I decide to make a triangle around this sample:
I then select the sample on the 3rd row (from the bottom) in the 2nd position, thus relatively centered on my triangle.
Here is the enlarged sample:
Finally, one realizes that the result on a larger scale of the enamel thus sought is not, in this case, identical to the research previously carried out. However, I choose to keep it by naming it oil red and not oil drop. I decide to continue the research around this glaze while keeping this one...
To find this glaze that I call natural green, my starting point is my Tenmoku recipe. I removed the metaloxide (iron) to experiment with the different oxides in my possession at different concentrations. This type of experimentation allows me to scan a few possible colors on a particular position in a diagram. We often get a lot of waste, but sometimes a notable result appears:
These samples have nickel as the metal oxide. Many times, I had noted tests around browns but I had the good surprise to see a green appear. And what's more, surrounded by a brown as the glaze thickness decreases. This bodes well for some beautiful pieces! So, I decided to explore this track by using the method of research of the cross (Removal or addition of a part of SiO2 or AL2O3).
The result is more homogeneous with a little more alumina or a little less silica. This is why I am continuing my research in this direction by conducting new tests. First with the addition of a little more alumina then by removing silica. Here is the result (we find our cross on the top left):
I choose to select the bottom middle sample which has a beautiful green color that can be seen in nature:
