Scientific investigations focusing on the appearing shapes of the pure copper lumps observed in or on the ancient bronze mirrors

We carried out the scientific investigations of the 16 ancient bronze mirrors produced mainly in the early and the late Hun Era in China, and the following results are obtained; (1) Among the 16 ancient bronze mirrors investigated here, pure copper deposition lumps were observed in or on the 15 mirrors except for one. (2) The rates of density reduction obtained from the measured and the calculated densities corresponded to the degree of corrosion of the mirrors. (3) The shapes of appearances of pure copper lumps in the mirrors show various modes, i.e., depositions like layers, large or fine particles, or depositions like string or flash of lightning just burring the cracks in the mirrors. (4) The environment of the pure copper depositions accompanies the metallographic irregularities occurred by the corrosion in the clay. (5) The oxide copper (Cu₂O) layers and particles were observed in the mirrors showing just the same shapes as those of pure copper depositions. (6) Non-corroded matrices of the all bronze mirrors investigated here contain about 2 mass% of Pb, 18 to 26 mass% of Sn and the residue of Cu.