A roll of Kodak’s late lamented Ektachrome 100D film was solarised half way through the first development stage (E6 processing). This causes a partial reversal of tones from dark to light and the film has a characteristically negative / positive look. This technique works best on colour reversal film.
From a no.w.here hand processing workshop. Visit us http://www.no-w-here.org.uk/index.php