The Transient Growth of Ammonium Chloride Dendrites

We report measurements of the initial growth and subsequent transient response of dendritic crystals of ammonium chloride grown from supersaturated aqueous solution. Starting from a small, nearly spherical seed held in unstable equilibrium, we lower the temperature to initiate growth. The growth speed and tip radius approach the same steady state values independent of initial seed size. We then explore the response of the growing dendrite to changes in temperature. The crystal adjusts quickly and smoothly to the new growth conditions, maintaining an approximately constant value of $v \rho ^2$ throughout. Dissolving dendrites, on the other hand, are not characterized by the same value of $v \rho ^2$.