volume cooled the liquid drop samples were cooled by plunging them from air into a dewar flask of liquid nitrogen or propane the same method that is used for flash cooling protein crystals for cryocrystallography fig1 shows the minimum glycerol concentration required to obtain a vitrified sample upon plunging into liquid nitrogen open circles are data collected by plunging drops held in tungsten wire loops for volumes above 1 u03bcl or in microfabricated polyimide loops below 1 u03bcl into liquid nitrogen at t v 77 k without removing the cold gas layer solid circles represent data collected by spraying drops onto the bottom of a 25 u03bcm thick copper cup and then plunging the bottom of the cup into liquid nitrogen vertical lines indicate corresponding linear dimensions of cubic samples the data for direct plunging of drops in liquid nitrogen show that the glycerol concentration and therefore the sample cooling rate saturates for volumes below 0 1 u03bcl indicating that there is no advantage reduction in glycerol concentration to using smaller volumes a similar saturation is observed when samples are cooled in liquid propane held at temperatures just above its melting point in contrast the data obtained using the copper foil cup do not show this.