Needle crystals characterized by hollowness and fast crystal growth can be readily produced via phase transformation of certain hydrates when immersing in an antisolvent. Former research indicated that the diameter of tubes produced by dehydration of the model substance sodium-2-keto-L-gulonate monohydrate in methanol can be controlled by the initial antisolvent composition. However, recent investigations using single crystals demonstrate that the outer diameter of the tubes can be decreased even further at unexpected low water contents. Furthermore, a new model based on the obtained results in this study is proposed for the currently unknown initial step (nucleation) of the growth of hollow needle crystals.