C117 Xiao wen's wild desire
"Actually, the hardness of the blue and red bricks are similar. It's just that the cooling methods are different after burning them. Red brick is a natural cooling, simpler, so production of red brick more. Brick is water cooled (in fact, it is a kind of anaerobic cooling). As long as you maintain the anaerobic state, there is no difference whether you use water or nitrogen)