I've created a comp in which one of the layers is a light beam created using the Ramp effect and a mask - the black end of the ramp correctly shows as transparent against a test background in the composition.
HOWEVER... If I then pre-comp it (after removing the background), then insert it into my main comp, the transparency has gone and shows as black against the main comp's background.
After doing more test, it looks as though Ramp does not retain transparency once pre-comp'd. Is there another technique I should be using?