Described is a classic cold-bluing technique suitable for refinishing firearms, especially double-barrel shotguns assembled by soft-soldering. Techniques of cleaning and polishing preparatory to bluing are detailed, along with appropriate cautions. The bluing solution is based on classic methods and is composed of 6.4 grams hydrochloric acid (of 1.19 g/cc density), 8 grams nitric acid (of 1. 42 g/cc density), 25cc distilled water and 1.6 grams pure iron filings, plus enough water to make 100cc of solution. Except for mentioning the need for adequate ventilation and loxic fumes, cautions on preparation of the solution and its use are inadequate. -- AATA