Patination is enhancement of bronze by the chemical application of color. Three water soluble compounds form the basis for most patinas: Ferric Nitrate produces reds and browns, Cupric Nitrate creates the greens and blues and Sulphurated Potash produces black. Each foundry develops its own proprietary (and carefully guarded) patinas that result from a carefully orchestrated blend of different chemicals, pigments and application technique. Wide ranges of colors, both transparent and opaque, are available to the experienced patineur. The final step is putting a thin coat of clear wax over the bronze to enhance and preserve the patina.