A new approach to automating droplet freezing assays is demonstrated by comparing the ice nucleating efficiency of a Kfeldspar glass and a crystal with the same bulk composition. The method uses a pyroelectric polymer PVDF (polyvinylidene fluoride) as a thermal sensor. PVDF is highly sensitive, cheap and readily available in a variety of sizes. As a droplet freezes latent heat is released, 5 which is detected by the sensor. Each event is correlated with the temperature at which it occurred. The sensor has been used to detect microlitre volume droplets of water freezing, from which frozen proportion curves and nucleation rates can be quickly and automatically calculated. Our method shows glassy K-feldspar to be a poor nucleator compared to the crystalline form.