An aqueous bath for imparting a brown surface coating to brass workpieces is provided by an aqueous solution of cupric carbonate; a thiosulfate or hydrosulfite color modifier; an organic color intensifier;and ammonium hydroxide in an amount sufficient to provide a pH of about 10.5 to 12.5. The workpieces are immersed in the bath, preferably at ambient temperature, for a period sufficient to develop a uniform brown finish thereon. The color intensifiers may be aliphatic and aromatic carboxylic acids, aliphatic and aromatic aldehydes, aliphatic and aromatic ketones, aliphatic and aromatic amines, aliphatic amines, aliphatic alcohols, oxidation-resistant hydroxybenzene compounds, aromatic phosphoric and sulfonic acids. -- AATA