This test is for the piece above, and I would like to do some test about underglaze. I quite like the matt clay-like finishing, and underglaze won't flow down which is suitable if I want to do gradually changed colour.
Because I bought some body stains before that at the beginning, I wanted to make underglaze by myself. Through my research, it seems that underglaze and engobe basically are the same. If the piece hasn't been bisque fired, I can use coloured slip mixed by slip and stain, which would be easier. However, test pieces and the piece above are all fired, and slip won't be able to hold the clay body that I have to use engobe. I found some recipes online which are following attached, but we don't have some of the materials in the glaze room. And I couldn't find relevant information in the library. In the end, I decided to buy some underglazes from Tiranti.
Here are the test pieces. Their colours look quite nice which are what I want. Hope they can be like this after firing,
Later, I managed to fine a recipe from the book I borrowed from library today that I maybe can try it next week. This book is called The Potter's Bible, by Marylin Scott. It is really clear and straightforward which is nice for a beginner like me.
White Stoneware Engobe
Potash Feldspar 10
China Clay 10
Ball Clay 5
Nepheline Syenite 5