When I’m working with more than one color at a time, I do set up a separate sifting area for each color. (PHOTO G) That way, I can pour my excess enamel back into its own container. Should your excess enamel become contaminated (i.e., more than one color become mixed together), either discard it, or keep a separate container of mixed colors to be used as counter enamel on future projects.
A NOTE ABOUT FIRING TIMES AND TEMPERATURES
Every kiln is different, every type of enamel is different, and every project is different. You will have to experiment with your own kiln and your own sifting technique to know precisely how much enamel to apply, how long to fire your piece, and at what temperature. Thompson Enamel’s 80 mesh, lead-free vitreous enamel, the brand used overwhelmingly by enamelists in the US, needs to reach at least 1450 degrees to fuse (Thompson has a great Help and Information page on their website for more information about their products).
But enameling is not an exact science and different colors may respond differently. Enamel that contains lead or enamel from British or Japanese manufacturers may need to fire longer or hotter. The gauge of the metal that you’re using can affect firing times as well.
Refer to your kiln’s manufacturer for their recommendations for setting your kiln’s temperature; most enamelists are comfortable firing between 1450-1520 degrees Fahrenheit (788-827 degrees Celsius). Remember that factors as simple as how long you hold the kiln door open may affect firing time.