We introduce a simple method to explore the efficacy of thermal styling, By using a temperature gradient curling iron we rapidly explore a range of thermal treatment conditions. The thermodynamic literature on the glass transition in keratin fibers explains the surprisingly limited role of elevated temperature in improvements in the efficacy of holding the styled curvature of the fibers. The onset of damage, however, is strongly temperature dependent. This combination of measurements of damage and efficacy shows the range of conditions over which thermal protection products must be functional.