Processing and Formatting Effects > Flame FX > Edge Detect >
Blending Settings

Blend Mode option box
  Select an operation to blend the input image with the matte created by the edge detection, and the input matte (if the Use Matte button is enabled).
Edge Transparency field
  Enter a value for the transparency applied to the edges.
Use Matte button
  Enable to use the input matte to constrain the blending of the input image and the matte created by the edge detection.