Why does play dough dry out and harden?

Play dough dries out and hardens primarily due to the evaporation of water content. When exposed to air, moisture gradually escapes, leading to a loss of plasticity and flexibility. Additionally, the ingredients in play dough, such as flour and salt, can absorb moisture from the air, further contributing to the drying process. To prevent this, it's important to store play dough in an airtight container.