Plano-convex ingot

Traditionally bun ingots were seen as a primary product of smelting, forming at the base of a furnace beneath a layer of less dense slag.

[13][14] High purity copper bun ingots found in Late Bronze Age Britain and the Mediterranean seem to have undergone a secondary refining procedure.

The metallographic structure and high iron compositions of some plano-convex ingots suggest that they are the product of primary smelting.

[18] Although all bun ingots share the same basic morphology, the details of their form and the texture of their convex base is dependent on the mould in which they cooled.

[21] Several offshore finds of probable LBA date suggest that copper bun ingots may have been traded by sea during this period.

[23] A second major group of British bun ingots date to the Roman period and are found mostly in the copper-rich highland areas of Wales and in Scotland.

[4] The Roman Bun Ingots are less pure than the earlier LBA examples and Tylecote suggests that they may be a direct product of smelting.