Viscosity: Viscous effects are basically frictional in nature. They oppose the flow. This can be seen from the equation for terminal velocity, wherein an increase in the viscosity of the carrying liquid will cause a decrease in the terminal velocity of the bubble. The more viscous the carrying fluid is, the slower the rate of separation.Specific Gravity: From the equation for terminal velocity, we note that as the difference in the specific gravities of the liquids increases, the buoyancy force increases and therefore improves separation. If the specific gravity of the oil approaches that of water, then the buoyancy force approaches zero.Temperature: The viscosity and specific gravity of a liquid are direct functions of temperature. For example, if the temperature drops from 18°C (65°F) to 10°C (50°F), the specific gravity of the water will increase by 0.12% and its dynamic viscosity will increase by 25%. The rising bubble will experience a net increase in drag and will rise at a slower rate. Therefore, separation is more effective in warm water than it is in cold water.Pressure: Liquids are generally incompressible; pressure would have very little effect on density and viscosity and therefore would not affect separation.