What name is given to colored gels that have lost their color or melted due to use?

The term used to describe colored gels that have lost their color or melted due to use is "burnout." This occurs when gels are exposed to extreme heat from stage lighting over time, causing them to degrade. Burnout is a common issue in the theater and live performance settings, where lighting instruments can generate significant heat. Identifying a burnout is important as it indicates the need for replacement to maintain color quality and lighting effects.

The other terms listed do not relate specifically to the degradation of colored gels. For example, a "boss plate" usually refers to a piece of equipment in lighting design and control, while a "book flat" is related to scenic design. The term "blacks," often referred to in theater, pertains to black fabrics used to block light or create a backdrop, rather than the condition of colored gels. Recognizing these distinctions helps in understanding the technical aspects of stagecraft and lighting design.