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March 25, 2014

Distillation Temperature

We recommend reading "How are Commercial Spirits Made?" prior to reading this article, as it provides a good overview of the topic of distillation. For those already familiar with the basics, read on!

Before we get started, a reminder: Distilling alcohol is illegal without a federal fuel alcohol or distilled spirit plant permit as well as relevant state permits. Our distillation equipment is designed for legal uses only and the information in this article is for educational purposes only. Please read our complete legal summary for more information on the legalities of distillation.
 

The Boiling Temperature of Ethanol

We get a lot of questions about distillation and temperature. There is a lot of information stating that the boiling temperature of ethanol is 174 degrees Fahrenheit. However, this is only partially true. The boiling temperature of pure ethanol is 174 degrees F. The boiling temperature of ethanol in a wash, that is to say, ethanol mixed with water, is completely dependent on the ratio of ethanol to water. The more water there is in the solution, the higher the boiling temperature. 

Commercial distillers that measure liquid temperature while distilling may have noticed that liquid temp can often be much higher than 174 before a still starts producing. Again, the boiling temperature of a solution that is 100% ethanol is 174 degrees. However, if a commercial distiller has a solution that is 50% ethanol and 50% water, the boiling temperature will be significantly higher. In fact, in a 50/50 solution of ethanol and water, the boiling (liquid) temperature of ethanol will be about 180 degrees.

Should a Still Start Producing Alcohol At 174 Degrees Fahrenheit? 

One question we hear a lot is "Should I see alcohol coming out of my still once the temperature reaches 174 degrees F?" The answer to this question is "No, a commercial distiller should not." Why? As we mentioned, the boiling point of pure ethanol is 174 degrees F. Wash in a still is not pure ethanol. If it was, why would one be distilling it? A first run wash is generally never any stronger than 20% ethanol. The rest (80%) is water. More likely it's something like 10% alcohol (ethanol) and 90% water. 

A solution that is 10% ethanol and 90% water is going to have a boiling temperature of about 197 degrees Fahrenheit. A wash that only has a starting alcohol of 10% ethanol won't boil anywhere near 174. The temp will have to be much higher than that before alcohol starts coming out of the still. For those that don't know how to determine the alcohol % of a wash, read our How to Use a Hydrometer article.

To determine the exact temperature at which ethanol will start boiling in a wash, check out this chart (Source: Craft of Whiskey Distilling by the American Distilling Institute). It shows the liquid boiling temp of ethanol based on the concentration of ethanol in a solution. For example, in a wash with a starting alcohol of 20%, ethanol won't begin to boil until liquid temp reaches 190 degrees F. Also, keep in mind, the data on the chart above only applies for distilling at sea level! The higher the elevation, the lower the boiling point. 

 Ethanol Boiling Point Graph

Should a Still Maintain a Constant Temperature During Distillation?

Another question we hear is "should I keep my still temp exactly 174 F during a distillation run?" The answer to that is "no, absolutely not." Why? Well the answer has a lot to do with the chart above. For example, if a commercial distiller starts with a strong wash that has a starting alcohol of 20%, they can expect that ethanol will begin to boil out of the solution once liquid temp reaches about 190 F. As a commercial distiller let's their still run and more alcohol is extracted from the wash, the wash alcohol % drops accordingly. Lets say that half way through the run half of the alcohol has been taken out of the wash and the wash is at 10% abv. Well, at that point one can expect liquid temp to have increased to about 198 F. The bottom line is that as a still runs, the temp constantly increases. 

Where Should a Thermometer Be Installed on a Still?

We prefer to install a temperature probe in the boiler, at the very least. Always make sure a 100% copper adapter and a stainless steel thermometer is being used. Adding a secondary thermometer at the top of the column to measure vapor temperature is helpful too. We recommend having one in both locations as it makes distilling a lot easier.

Thermometers at the top of the column

The two thermometers read different temperatures during the run, but they are also measuring two different things. The boiler temperature is measuring the temperature of the liquid inside the still, while the vapor thermometer is measuring the temperature of the vapor inside the column.

Keep in mind that the temperature reading is highly dependent on where the reading is being taken. First of all, never use an infrared thermometer to try and measure still temp. They aren't accurate. They measure surface temp of a still, not of the liquid or vapor inside. Also, if a still is polished and has a shiny surface, the signal could be bouncing off and giving a reading of ambient surfaces.

Should Vapor Temperature and Wash Temperature be the Same?

Vapor temp and wash temperature should be very different. Once vapor begins to form in the pot and it migrates up the column, the vapor temperature probe at the top of the column (if one is installed there) will rise from ambient temperature to 175 in a matter of a minute. Hypothetically speaking, at this point the boiler thermometer may read something like 195 F (again, depending on the starting alcohol) and the vapor probe could read as low as 175 F. There will always be a big difference between the two temperatures (boiler and vapor) which is not a big deal.

How to Use Temperature During Distilling

Temperature is mostly helpful determining when to seal the still, to know when it's about to start producing, and to know when it's about done producing. As far as making good product goes, we still think the most reliable method is to adjust heat based on the amount of product coming out of the still. A commercial distiller should be looking for steady, fast dripping, not a stream. Also, keep an eye on proof. If the proof is super low at the beginning of a run, there is either very low starting alcohol, or the still is running too hot. We use our parrot kit to constantly monitor the proof of the product coming out of the still.

  • I have had alcohol coming off my still at 122 degrees. And I shut my still down at 191 degrees so I don’t have to worry about tails

    Posted by Chad on November 13, 2021
  • Hi, I’m distilling a (abv 12.5%) molasses wash, and sometimes after heating up to about 85*C it comes out of the spout a liquid very similar to the wash, very dark and 0% alcohol . This doesn’t happen with every single run and I’ve had runs with 60 ABV.
    Am I doing something wrong?

    Posted by G on November 13, 2021
  • Fahrenheit. sigh cmon america

    Posted by Pellet on November 13, 2021
  • Listen my column temp is reading about 100 and my PID IS ABOUT 165. I don’t think that’s rite. I’m using copper mesh in the column just one piece. Should I let it cool and take the mesh out?or maybe increase heat? I don’t have the mesh packed tight

    Posted by JEnnifer on November 30, 2020
  • What temperature should the heat source be set at? I use a hot plate but am unsure about how hot it should be. I see people using stove heat at full blast and that doesn’t seem right?? What do you recommend?

    Posted by deana on July 14, 2020
  • which temp gauge should i look at when cutting the foreshot liquid or vapor?

    Posted by davidb on May 13, 2020
  • Wat temperature must my stil pot run to produce best alcol

    Posted by Renier on May 12, 2020
  • what should the water temp be at the condenser? And How many GPH pump would you suggest for a closed loop system?

    Posted by Leo on February 06, 2020
  • Great website,lot of good info 👍

    Posted by Rick on February 03, 2020
  • Is mash temperature of 90 degrees Fahrenheit too hot to ferment mash for distillation?

    Posted by John on July 29, 2019
  • So if I replace the Thermometer at the top of the column. With a heat sensor probe connected to a controller driving the heater and set the controller To 175f that should drive the boiler to maintain pure ethanol at the output. The controller is accurate to +-2 degrees and I would use an external pump to control circulation in the boiler to keep everything even in temperature.

    Posted by John on March 26, 2019
  • Hello i have a 1 gall still how much will that produse using wine?

    Posted by keith on December 31, 2018
  • Condenser cooling water temperature. (high proof alcohol distillation)

    does anybody have a good rule of thumb for condenser cooling water temperature? my ambient tap water temperature runs at 70-90oc (depending on season). will this be ok?

    also to reduce water wastage (and cost) I would like to run to my condenser cooling water from in a closed loop, i.e charge a large bucket of water and pump off this and reject to it. is this possible?

    thanks mark

    Posted by Mark on May 16, 2018
  • Hi bought A distiller with a 100liter tank,2kw heater x2,control box with temperature controlled
    4” copper tee with sight glass x4
    4” copper bubble cap x4
    4” dephlegmator x1
    4”-2”triclamp reducer with thermometer x1
    2” elbow 180 degree x1
    2”dehlegmator x 1
    Parrots x1
    2”-1” trick amp reducer
    1” ball valve
    Kindly with this specifications I have put across to you give me a comprehensive advise am starting up this project in 2months in my country on a small scare though Commercal for the first time am going into brandy, vodka, whisky, spirits, I want be using ethanol, water what flavors Should I use to make products have best test your advise will be highly appreciated
    Regards
    Richard Peter

    Posted by Richard Peter on January 23, 2018
  • If you have a 5 gallon still 1 gallon thumper a 15 coil worm and a electric hot plat all copper y cant we get a steady stream out of it

    Posted by Mike on December 04, 2017
  • thank you emmet-got it.

    Posted by Mike on November 14, 2017
  • Ditto on shishas post. do some research you guys. its all fun and games until someone gets hurt

    Posted by Dan on October 13, 2017
  • I must say, some of you scare me with your techniques.
    Personally, I have a 15 gal stainless beer keg, home made 1" reflux column, recirculation of water thru a 50 gal tank.
    I heat the keg up slowly, when liquid starts dripping, I adjust the fire down til I continue to have a steady drip. I then turn on my reflux coils and monitor the head of the reflux temp. It usually stays running at 175 degrees. Once my head temp reaches 190, I then start separating the tails. Off 13 gals mash, I normally get 1 1/2 gals of 165-180 proof in 4 hours.

    Posted by Mike on May 13, 2017
  • hi guys hope all go well. have a question?
    a friend gave me a old yogurt maker (stainless) he modified it a bit so that copper pipe can be inserted in top, it has a electronic heater inside, he said i must fill it with water and switch it on and try too get the temperature to 70 degrees celcius( it has a build in thermostat that can be tuned). is this the correct method for distilling? i used to use a preassure cooker but this is a whole new level of distilling for me. hope to hear from ur guys, great site!!

    kind regards

    Posted by Ruan on May 13, 2017
  • For real quality as soon as you start to drip check the temp. And hold it there. When it starts to rise you have no more quality in your drip. I like to make 3 runs then cut it with the purest water I can get. I end up with about 90 proof of very drinkable shine.

    Posted by PAul on March 29, 2017


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