Desiccation crack formation is affected by the presence of electric fields. We show here that the field effect not only is at work while the power supply is on but also leaves a memory even after switching off. The time required for the first appearance of cracks is shown to depend on the voltage of the field as well as the time duration of exposure. We model the system as a leaky capacitor described by a fractional order derivative in the constitutive equation. This gives a good fit to experimental data and explains the memory effect.