magnesia cupels  temperature-cs ceramic

The heat of oxidation of the lead causes the temperature of the button to rise considerably above that of the cupel and the muffle, in the case of bone-ash or cement cupels, but only slightly above the cupel temperature with magnesia cupels. Therefore with bone-ash or cement cupels the muffle temperature should be lowered during the driving period in order to keep the lead temperature from rising more than the minimum necessary for the reaction to proceed.
...
With magnesia cupels the temperature gradient from lead to cupel to furnace is not so great as with bone-ash or cement cupels, because of the greater heat capacity of magnesia compared with the other materials. The button will appear slightly hotter than the cupel, but the observable difference is by no means so great as with the bone-ash or cement cupels. Since the minimum lead temperature must be the same in all cases the muffle temperature with magnesia cupels must be higher during the driving period than with other types.
Muffle temperatures of 870 to 880¡ãC, as measured ½" above the muffle floor behind the cupel, are recommended for the driving stage of cupellation in magnesia cupels, and temperatures as low as 830¡ãC may often be successfully used during the period of most active driving

magnesium oxide and bone ash cupels	magnesium oxide and bone ash cupels	Magnesium sand cupel	Ceramic Couple
Plate cupel	Fire assay cupel	magnesia boat crucible	magnesium oxide crucible

total : 125    page : 1 / 8             turn to