Etched-foil flexible heaters provide excellent temperature control and uniformity in a broad range of applications. Their thin profile and foil elements contribute to fast warm-up, consistent heat distribution, and extended heater life. To achieve ideal performance, however, the heater must be properly configured to the thermal demands of the application. The complex physics of heat transfer makes it difficult to predict all aspects of system performance in the early design stages. Therefore, applications requiring tightly regulated temperature may require extensive prototype work. This white paper presents some tools and techniques to assist in thermal prototyping.