Our cupels are made from quality dead burnt magnesia (MgO) and work great for cupelling lead in the fire assay process to determine gold and silver content of ores or other precious metal samples. They can also serve as high-temperature melting dishes for melting metals.
Each order contains six individual 7A cupels.
Approximate dimensions of individual cupels are: 1-9/16" across the top outer diameter (39.7mm), 1-3/16" across the bottom diameter (30mm), and 1-1/8" in height (28.5mm).
#7A cupels weigh approximately 61g each, plus/minus about 1.0g.
Magnesia cupels can absorb approximately 70-75% of their weight in lead oxide (PbO) which translates to roughly 42.5g of lead oxide absorption for a 7A cupel or 39.5g of metallic lead. Making them perfect for cupelling lead buttons up to 35g in weight. It is not recommended to attempt to absorb the maximum theoretical absorption potential as this may risk cracking of the cupel and spilling of the molten lead.
When used for cupelling lead, each cupel is meant for a single use.