What is a common physical characteristic that affects spray droplet size?

A key physical characteristic that affects spray droplet size is the viscosity of the mixture. Viscosity refers to the thickness or resistance to flow of a liquid. When the viscosity is high, the mixture flows less readily, which can lead to larger droplet sizes when sprayed. Conversely, a lower viscosity allows for smaller droplets because the liquid can atomize more effectively under pressure.

While temperature and humidity can influence the behavior of spray droplets — for example, temperature can affect the viscosity and evaporation rate, and humidity can affect how quickly droplets dry — they are not as directly related to the formation of droplet size as viscosity is. Therefore, focusing on viscosity provides a clear understanding of how the physical characteristics of a spray mixture impact droplet size.