One of the jobs they did was the mushroom clouds for a movie - called The Day After, IIRC.
They made the mushroom cloud events in a chamber maybe 36" tall.
For "The Day After" (1983), they wanted to use actual nuclear test footage but (I think) the gov't wouldn't allow it for some reason. (I seem to recall that they insisted that the film show explicitly that the USSR attacked first, and the director refused).
Anyhow they squirted ink into a tank of water, then turned the shot upside down so it looked like a climbing mushroom cloud.
