These Contour/Grisaille colors are acid- and akali-resistant and are especially suitable for stained glass. The colors are mixable with each other. Apply by brush, airbrush, or screen printing. For brightening or reducing the firing temperature, add Flux 9150. For best results, heat up slowly, minimum 1 hour, fire 10-15 minutes, then cool down slowly, minimum 1 hour. It is possible to fire these paints up to 700°C (1292°F).