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For the assay of precious metals The assay of gold alloys by cupellation is the standard method used by the United Kingdom Assay Offices and a reference laid down by the International hallmarking Convention. The range of batch furnaces from Carbolite has gained an international reputation for close temperature uniformity, low heat loss and maximum fume control. The Cupellation furnace Construction: The outer case is fabricated from zinc coated steel sheet which is finished with an easy to clean hard wearing stoved epoxy/polyester coating. The work chamber, roof and hearth are lined with silicon carbide tiles which will withstand the corrosive lead fumes emitted during the process. Double skin construction ensures a safe and cool outer case temperature. Heating elements: Silicon carbide heating elements are mounted above and below the work chamber providing even heating of the cupels. Silicon carbide elements offer high resistance to thermal shock and offer an extended working life at elevated temperatures. Insulation: The combination of low thermal mass ceramic fibre and hard wearing refractories provides maximum thermal efficiency. |
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| Door: The insulated door, with observation hole, operates with a vertical counterbalanced action keeping the hot door insulation away from the operator. A positive break safety switch activates isolation of the chamber from all power lines when the door is opened. Chamber Air Flow: The air, which is controlled by an adjustable valve at the rear of the furnace, is preheated by passing over the lower elements prior to entering the chamber. This ensures rapid heat transfer and even temperature distribution throughout the work chamber. Chimney/Extraction System: Fumes are extracted through an insulated exhaust duct and a removable container, situated below the chimney, collects any condensed lead. The furnace should be positioned beneath an efficient extraction system preferably fitted with a proprietary lead filter. Controls: The furnace temperature is regulated by a three term microprocessor based controller which provides temperature stability of +/-1°C. A back up two term overtemperature controller protects the heating elements and furnace load. A 24 hour, 7 day time swith is fitted as standard. |
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| Specification
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Charge Capacity The charge capacity for the range is based on cupel size no. 8 (44.5mm dia x 30.2mm h) and cupel size no. 6 (35.7mm dia x 28.2mm h). Obviously, loading will depend on the cupel size used.
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