I usually put one cone and a small test piece for firing. In the picture there are two cones where one of them is just for test. I make my own cone, so every cones running out and make a new one, it must be tested by firing for temperature accuracy. For small test piece, I made it from bisque ware which have been glazed and a hole in the middle, so you can draw it out by a steel rod.
The position of cones must be seen clearly enough from peep hole. In the bottom picture, you see the silhouette of the cones. Sometimes when temperature reach vitrified point, cones are not clearly enough to be seen by naked eye, it's a like the heavy fog around the pot. So to figure it out you can blow gently the peep hole by mouth in several times until the chamber atmosphere clear again. Remember to not get too close to the peep hole when you blow it, otherwise your mouth will be burned.
Specialized in table ware and interior element ceramics Spesialisasi membuat keramik table ware dan elemen estetik dalam interior