Montage - one shot in sharp focus overlaid with another shot totally out of focus. The out of focus shot has to be in the focus direction that causes the blur to expand (not shrink). The expanded blur, when overlaid on the sharp focus image, is what gives the final montage its glowing outline.
I've got to stay out of craft stores - collecting too much junk. Tomorrow we'll exchange the black backdrop paper for sand. The next day - a thin layer of sand on a glass top table with colored light shining up from below (I have gels that haven't been used).