Do not attempt to use silver bronze, silver paint, or even silver leaf, for nickel leaf is the only substance which has sufficient lustre _and will not oxidize_, and turn yellow.
If the whole body of a fish is dark, and without silvery tints, it is, of course, unnecessary to use leaf, for the lustre can be obtained by varnishing over the paint.
In many fishes, such as the scaled carp, for example, Marsching's gold paint or Japanese gold can be used directly on the scales (_after_ the entire fish has had a thin coat of Hendley's enamel varnish), and the silver paint can be used to good effect in edging the scales. On the belly, however, which is silvery white, nickel leaf must be used. The heads of most fishes are so dark as to render the use of leaf unnecessary upon them, and of course it need not be used on the fins.
PAINTING PLASTER CASTS OF FISHES, REPTILES, ETC.--When a cast is first taken from the mould, it will nearly always be found that its surface is pitted here and there with little round holes caused by air-bubbles. The process of wetting the inside of these holes, and carefully filling each one with mixed plaster Paris is called "pointing up" a cast. After this has been carefully done, and the form and surface of the white cast is perfect, if the cast is thoroughly dry we are ready to begin to paint it, and proceed as described in the preceding section.
In case you find it impossible to use nickel leaf on your fishes, you can do very good work without it, except that the silvery parts will not be really silvery, and the white paint put on will gradually turn yellow with age. After you have given the specimen a good coat of colors (using zinc white for the silvery parts, because it is more permanent than other whites), varnish the specimen all over with a kind of heavy white varnish called Siccatif de Harlem, or, lacking that, enamel varnish. This will dry in about twenty minutes, after which paint the object over again, this time with extreme care in the final touches. In painting fishes and reptiles, there is a vast amount of detail to be wrought out, and constant blending of colors. On many fishes each scale must be marked off and painted separately. In blending the edges of two adjoining colors, it must be done with a clean brush--a small one, of course--with either a quick, nervous motion along the line of contact, or else a steady sweep, according to circumstances. When the brush gets full of paint, wash it out in benzine (_not_ turpentine), because it quickly becomes clean, and dries perfectly in a moment.