[121] “Zeitschrift f. Ethnologie,” XXXIII. 1902, p. 431, and XXXIV. 1903, p. 791.
[122] “Sitzungsberichte,” 1881-82, p. 10 et seq., and 16 et seq.
[123] In this acid treatment bare hands may be used, but care must be taken to avoid splashing clothes or linen, which will cause red or yellow spots. These are best removed by the immediate application of ammonia, but the yellow spots can only be removed by oxalic acid.
[124] [Germ. “Hammerschlag.” The iron scales which chip off from heated iron at a forge or blacksmith’s shop. Transl.]
[125] No. 17, 1897, p. 333 et seq.
[126] A number of modifications in the metals employed and the composition of the bath have been suggested. Setlik (“Chemiker Zeitung,” XXVII. 1903, p. 454) imbeds iron objects which have a very weak core in a zinc-wire basket immersed in a magma of zinc dust and caustic soda. Personally I should prefer not to attempt a reduction process in such cases, but should rely rather upon mechanical removal of the rust, soaking and impregnation. For the treatment of bronzes this observer prefers the Finkener method (q. v.) and suggests caustic soda, sodium chloride, or ammonia chloride, instead of potassium cyanide as the electrolyte. Rhousopulos (“Chemische Zeitschrift,” II. 1903, pp. 202 and 364) uses zinc and hydrochloric acid, and when dry gives to the bronze a coating of wax. I should deprecate the use of either of these substances, the hydrochloric acid because of the difficulty of completely removing it by steeping and the danger of subsequent decomposition of the bronze, the wax because the contained fatty acids may act upon the metal.
[127] [The period required for complete reduction is, in our experience, often considerably longer. We have sometimes found an 8% soda solution more satisfactory. Transl.]
[128] Krefting’s method affords an excellent illustration of the truth of my remarks in the preface that the literature upon these preservation-methods is very scattered and in consequence has been hitherto but little studied. In 1892, when visiting the Museum at Christiania, I had the opportunity of examining some iron objects which had been treated by Krefting’s method. I then obtained his address, and Herr Krefting kindly communicated his method to me by letter, and in the following year forwarded a reprint of his article referred to above. In 1887 he had described his method to Appelgren by letter, but at that time he treated the object after reduction, washing, and drying, by impregnating it with a paraffin-petroleum solution. In 1897 Appelgren published this method, with drying and impregnation, in ignorance of Krefting’s publication in 1893.
[129] The bottle should not be closed by a glass stopper, but by a rubber bung, or by a cork coated with paraffin or wrapped round with parchment. Soda solution attacks glass, and especially ground glass; thus the stopper may become so firmly fixed into the neck of the bottle as to render its removal impossible.
[130] [Excavated by Dr Thurnam, 1848 (vide “Archaeolog. Journal,” Vol. VI. p. 27). Transl.]