Abstract
In most cases, when the green or dry sand specimen is exposed to the high temperature (700°, 900° and 1150°C), the natural molding sand begins to decrease in strength at the beginning of the exposure, but afterwards recovers from this decrease.
However, the sythetic molding sand specimen consisting of silica sand and bentonite does not decrease the strength even at the beginning of the exposure.
In some cases, the natural molding sand is prevented from the decrease of strength by adding the bentonite or mulling the sand.
