Moonshine Still – Vacuum Boiling Temperature Vs Pressure Chart
How to use this chart. Notice you need an absolute pressure of little under 1.4 psi to distill, or boil, ethanol from water. Why? Say room temperature is 68F or 20 degrees Celsius. Extrapolate the temperature to find the correct pressure. You can see that at standard atmospheric pressure of 14.7psi that ethanol boils off at 73 C, correct? So we will now extrapolate.
Temp factor=(tempHI-room temp)/tempHI= (32-20)/32= 0.37.
Now go to the pressure side. Proomtemp=temp factor*(pressHI-pressLO)+ pressLO. = 0.37*(2.0-1.0)+1.0= 1.4~ psi for 68 degree room. Although there will be small errors due to rounding, altitude, weather, distilling ingredients, ect, the chart is an approximation for your setup. All vacuum still setups are different and you will have fun finding your own sweet spot.
The above chart gives you guidance on how to distill liquids with your vacuum still. As you can see, you can actually distill at room temperature.
How to use: standard vacuum distillation practice is to hold one variable, temperature or pressure constant, while changing the other variable to distill the desired fluids.
For example, if you have a single stage vacuum pump then the easiest way to distill is with a hot plate; the pump would stay on constantly and use temperature as the variable to control distillation.
If you have a large vacuum pump, then you would keep the temperature constant and change the vacuum to lower the pressure to vaporize(boil) off the desired fluids. If the vacuum pump does not have a pressure regulator switch, than either add a pressure switch, or even better, a regulator. All else fails, you can turn the pump on and off to regulate the vacuum applied. You need a robust two stage vacuum pump to operate at or below room temperature. SLOWLY DISTILL IN ALL CASES.
Only operate any still outdoors. Obtain all required building, safety, federal and state permits and licenses before operating your still.