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Jun 08, 2022 View:

Whiskey Distillation Efficiency Problems

I have a distilling efficiency question - although our ferments are going well, and according to our calculations our mash should be about 6.5%, we are only get 3.5 gallons of alcohol out of the still, including heads, hearts, and tails, of the available 6.5 gallons. Let me show you the details.

Corn Whiskey

  Original Gravity -  1.065

  Final Gravity - 1.015

Our calculator tells us our starting abv is 6.56%. When we run we get about 6 gallons of 100 proof (heads and tails) and if we run out the tails to the end we get about 1.5 gallons of 60 proof tails.

By my calculation we are only getting about 3.5 gallons of our original 6.5 gallons out of the still?

We are using a 100 gallon column still, distilling on the grain, and agitating the whole time.

What can we be doing better?




I don't do grain-in but I would like to know how you accurately measured those gravities?

I am guessing that may be the calculation problem, but you also should get better than 3.5% yield, so there may be more that one problem.

I recall a sudden reduction in yield issue on this forum about 4 years ago, it turned out to be low quality corn.


We are using flaked corn from BSG.

With our mash we are using a refractometer and double checking with a hydrometer. Hydrometer can be a little annoying because of the solids present, but we essentially just minimize the solids in the hydrometer.

To clarify, we only use the refractometer for OG - the hydrometer for FG.


Edited by ColoradoDistiller

You might not be doing as bad as you think, if you factor for the volume displaced by corn in your still.  In other words, if you were to separate your corn (not fun) from your mash prior to distillation you might find that you have around only 60 gallons (rough guess) of 6.56% distiller's beer.  If you have the time/fermenter space, you could increase your yield by letting your fermentation go another week or so.  If your enzymes (gluco) are doing their job and with the proper yeast pitch rate it is possible to finish at .990-.995 specific gravity.  Hope that's helpful.


Can you provide your exact mashing protocol?



You should be able to get about 11% of your kettle volume per run in finished whiskey. So from a 100 G still you should yield about 11 proof gallons of hearts. This is all super rough numbers. 

You're saying you have a possible 6.5 gallons of 100% ethanol (6.5% abv of 100 G kettle). In proof gallons thats 13 proof gallons.  This is your theoretical ceiling at 100% efficiency (at 6.5% abv).  Impossible to achieve, but a good number to know.

You're saying you are actually achieving 3.5 Gallons.  Is this 100% ethanol? What proof?  Is this proof gallons? Best case scenario, If you're considering this 100% ethanol, you're looking at 7 proof gallons of total alcohol yield of a possible 13.  That's a problem. I agree. 

Your final gravity is way too high.  You're probably having a conversion issue during the mashing process, or fermentation issue.  Are you using exogenic enzymes? Are you using nutrient for your yeast?  What type of yeast? Is it temperature controlled?  Whats the pH at pitch? Whats the temp at pitch?  There's a lot of variables but these questions should help guide your research. If you get that FG down to below 1.005 you're now talking about 8-8.5% abv.  An abv between 8 and 10 is ideal for the separation of ethanol from water.  Water is a greedy molecule and will try to grab onto any polarity if finds. If you have more ethanol in solution (higher abv) you have more alcohol to water molecules and the alcohol can vaporize easier. This increases yield per unit of abv. That is to say you get more hearts per 1% alcohol the higher you go.  Don't start chucking more starch in the mash, however, because once you go over about 10% abv you're going to increase your fermentation time exponentially. 

Another note, refractometers read dissolved solids, but they're thrown off as the abv climbs. Alcohol refracts light differently than water. We are dry (below 1.005 sg) at around a 7-8 brix refractometer reading. That's about 1.025 gravity on the refractometer.  If you convert for the alcohol (The calculator here is the top result in google) you can then calculate your FG, then your attenuation based off your SG.  

Basically you should yield around 11 proof gallons of hearts. Thats about an 85% yield of hearts from your theoretical TOTAL alcohol at 6.5% abv. That yield will change (increase) based on the efficiency of your reflux, and still.

I would suspect in perfect conditions, at 8% abv, with feints recycling you're looking at 13-14 proof gallons yield for your setup on the low end. 


Out of curiosity rtshfd, what percent do you predict heads and tails (and I assume that number is without recycling any heads or tails)?  I run lower than that without recycling, higher than that with.

Reply:1 hour ago, jeffw said:

This is right in line with the topic I was going to post. I'll try not to hijack this too much :-)

I am curious if anyone who is recycling tails is doing it as a separate run, rather than putting it into each batch. If so, what yields are you seeing (expressed as PG recovered:PG in pot)?

As for your low recovery numbers, there are some other factors you may want to visit. Mash and fermentation efficiency are one. Do your stripping runs foam up? If so, you may have poor conversion or residual sugars. How are you measuring your potential alcohol? Do you do efficiency calculations at both stripping and at spirit runs? You should normalize your numbers to something like Proof Gallons per Bushel or PG per Kg, so you can compare. 

If you look at the copper in your still, do you see tiny spots of bluing? And when was the last time you checked or replaced the gaskets in the still? You would be shocked at how common vapor loss can be, and your losses are consistent with what I might expect from a small vapor leak. Also, what temp is your spirit when it leaves the parrot? And look for bubbles in your return/cooling water...condenser leaks are hard to trace, and can DESTROY yields. 

Last but not least, what proof do you make your cut to tails? If you are not recycling them, this can drastically reduce expected yields. 



Dodo Distilleries

Reply:On 8/17/2016 at 10:49 PM, Natrat said: