H490
Description
H490 is H550 with 3.5% added yellow iron oxide. The red color only lasts until cone 8.
Firing
H490 fired test bars. Top is cone 10R. Below that going downward: cone 10, 9, 8 oxidation. Thus, the oxidation red color only holds under cone 8. For reduction, the both fires almost black. By cone 10R, it is behind to blister and melt.
