A test specimen to determine the degree of firing in a kiln. It is the most necessary and difficult task to give the right amount of heat without excess or deficiency to the ware during firing, and it is a common difficulty for all potters. For this reason, a small object of the same quality as the fired product is placed in an appropriate place in the guide so that it can be easily removed with an iron rod, and taken out at an appropriate time to see if the product has reached an appropriate firing temperature. The Zegel pyramid, made by German researchers Segel and his collaborators, is a type of pyramid. It is planted in refractory clay and placed in a place where it can be seen through a color viewing hole. Since the cone is made by mixing various raw materials, the same effects are given to the cone as in the firing process, such as the speed of raising the temperature, characteristics of the gases in the kiln, and thermal effects, etc. This allows a good understanding of the firing state of the vessel, and recently many pieces are being fired with this method.
