Red Crayon is an opaque "what you see is what you get" (WYSIWYG). 

Working the color without encasement in the outer flame is ideal but quick passes in a sharp hot flame closer to your torch tip also works.  Red Crayon works smooth and melts down without any potential sublimation if you have a bit of patience and keep from concentrating a sharp hot flame on one spot.  It requires time to warm up and allow the heat to penetrate past the surface of the color.  In other words think of your flame as a small brush and move lightly around the area you intend to get molten in a spot heat situation. 

This color works well for blown and sculptural work and murrine.  When encased between two layers of clear glass you can blow out quite thin before color starts to become translucent.  Use with Indian Red Crayon, Orange Crayon, Rasta Gold Crayon, Yellow Crayon, and Acid Yellow Crayon for recreating fire in sculpted and blown glass.