Inkjet printings market has been growing for several years. Evaporation rate of droplet was explained relating to the boundary layer and condition near the droplets surface. However, no experimental result has been obtained. This study aims to investigate the boundary layer of ethanol-water mixture droplet and its effect on the evaporation rate by Z-type Schlieren visualization. Single and double droplet were tested and compared in order to identify the effect of the second droplet on the average and instantaneous evaporation rate. Double droplets lifetime was found to be longer than single. It is indicated that larger evaporation region formed on the top of the droplet means higher instantaneous evaporation rate. Boundary layer was found to be larger as ethanols concentration increased. Furthermore, larger evaporation region was found in higher ethanol concentration case and that described faster evaporation found in higher ethanol concentration.