After the burning process the specimen with three different firing temperatures, then the next step is to test the temperature of the clay maturity as described below:
1. Retrieve all test specimens that have been burned and separate formulas for each clay and firing temperature
2. Observe the test piece of grilled colors: pale, bright, or dark
3. Tap the test specimen to determine his voice: loud or not loud
From the results of the evaluation of the maturity test can be concluded whether the specimen is ripe, not overly ripe or even burn at a predetermined temperature.
a. When immature, the specimen should be tested again by fuel burn at a higher temperature or adding some kind of other material on the body mass of clay tested.
b. If too ripe, the test body will change shape, so that the fuel temperature needs to be lowered or the content of refractory materials such as kaolin, quartz slightly reduced body mass in order to obtain high-quality fuel that is suitable for the desired temperature.
The addition of other ingredients in the clay mass is meant to get a quality body mass, ie
a. If the body mass of refractory clay too, so it was not cooked at temperatures of fuel that has been applied, it is necessary plus materials or materials that are flux to lower the temperature of baked clay such as calcium carbinat, talc, body frit.
b. If too melted to change shape and become very dense at a predetermined temperature ripe, then the mass of dough clay body needs to be coupled with fireproof materials such as kaolin, ballclay, stoneware clay, quartz or refractory clay.
c. If the color of the clay body mass fuel will be made darker, you can add metal oxides such as iron, manganese, cupper, and so forth.