Non-Newtonian fluid is a fluid that changes its properties depending on velocity gradient. What does it mean? The more intense and rougher the impact on Zephyr is, the harder it is. For example, if you put pressure on Zephyr rapidly, it will become tighter. In this state it can bounce as a ball and doesn't fall apart. The softer the impact on Zephyr is, the more flexible and stretchable it is. Non-Newtonian properties are typical for fresh Zephyr that has spent some time in open air after long play. Zephyr that is already warm and saturated with moisture from your hands acquires properties of usual Newtonian fluids. It almost completely stops to react to rough impact but reacts to humidity and warmness, becoming soft, lightweight and fluffy.