W. W. Greener in "The Gun and It's Development" 1907 doesn't really address the contrast issue, and discusses both pattern welded and fluid steel browning
http://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA270&source The bronzed appearance of the finished gun barrel is obtained by a process of rusting the barrels, the rust being cultivated, then stopped; the complete oxidation of the surface renders the barrels less liable to rust by natural means.
The beautiful figure of the fine Damascus and laminated steel twist barrels is not surface-deep only; the figure runs completely through the barrel, as will be made clear by referring to the description of the process of making the iron for, and the methods of welding, the barrels. Consequently, it is impossible to get by browning any finer or more beautiful figure than is already in the barrel; it is possible, by inferior browning, to hide that figure, or so obscure it that recognition is barely possible. That fine gloss, seemingly the effect of lacquer or copal varnish, is nothing more than the highly-burnished surface of the barrel, which before browning was as highly polished as a silver mirror.
The colours which can be obtained vary from a light yellowish-brown, through various red-browns, to a deep Vandyck-brown. A rich plum brown is obtained if time is taken and a little black brimstone, say 1/4 oz., added to the above mixture. Spirits of nitre and nitric ether are sometimes used in lieu of spirits of wine.
The black-and-white brown may be obtained by using much diluted mixture, and touching up the barrel before boiling by sponging with water in which a little muriate of steel has been stirred. The colours can be heightened also by plunging the barrels in cold water immediately they are taken from the boiling trough. In all fine-figured barrels the coating of rust is necessarily very thin, or the figure could not be distinguished. This coating of brown soon wears off. The only remedy is to have a greater body of brown, hiding the figure, or to use the black-brown, as in military rifle barrels. This last brown is much more durable, and effectually protects the barrels from rusting by salt air, hence is much used on ducking, punt, and wild-fowling guns.
Steel shot barrels, when black-browned, show no tendency to rust, however much exposed to atmospheric changes. The black-brown is obtained in a shorter time, and a much stronger mixture may be used—as, for instance: 1 1/2 oz. spirits of wine; 1 1/2 oz. tincture of iron; 1 1/2 oz. corrosive sublimate; 1 1/2 oz. sweet spirits of nitre; 1 oz. sulphate of copper; 3/4 oz. strong nitric acid; 1 quart of water.
Before re-browning any figured barrel it is essential that the old brown be effectually removed. The barrel must be well polished again before re-browning, if that fine sheen so much desired is required; otherwise, simply rubbing off the brown with emery cloth, with fine emery in water, or by sponging the barrel with strong vinegar, will answer the purpose.
