Bringing life to the lifeless:
The Flour Sack was popular as an animation test at the Disney studio in the 1930s because it was more organic in movement than a bouncing ball, focusing more attention to weight, overlapping action and how the sack changes shape over time. It also forces one to think about timing and how to make this object move realistically in animation (Keslensky, 2005).
Many animators still use the flour sack as a practice and warm-up tool. There are not any strict guidelines for the flour sack exercise, except to adhere to the 12 principles of animation.
Word count: 100 words
References:
Keslensky, J./Tall Grass Radio Studios (2005) That Poor Misunderstood Sack of Flour. Available at: http://tallgrassradiostudios.blogspot.com/2005/05/that-poor-misunderstood-sack-of-flour.html (Accessed: 17th March 2020)