We may have been a little harsh on some of the processes and special effects used in the movie, so let's give credit where credit's due. One of the scenes in the film calls for the Wicked Witch of the West's hands to be engulfed in fire as she tries to remove Dorothy's shoes. Actress Margaret Hamilton had already been very clear about not working with fire again, and a different solution had to be found.
Ingeniously, someone had the idea to force apple juice out of the shoes, and then speed the film up to look like fire. The juice showed up on the technicolor film in perfectly the right shade, and it was actually a revolutionary idea which resulted in a (for the time) excellent looking effect. It also probably ruined a perfectly good pair of shoes, but we can forgive them that.