Make Your Own Stirling Engine Fuel

6 Cylinder Stirling Engine Powered ‘STEM’ Gatling Machine Gun


I have been asked how I make my own fuel for my Stirling Engines a few times now.


Being a home-made winemaker in my past, I simply brew alcohol up and freeze the liquid to get the alcohol, rather than trying to boil it out of the mash, just to make life easier and safer.

With alcohol-burning Stirling Engines it is generally recommended you use denatured alcohol as other products are added to alcohol to make it denatured to give it a foul taste and smell, but my home-produced alcohol is exactly the same without the extras.

On the other hand, you could use methyl alcohol (methylated spirits) which is the poisonous side of alcohol and brewing production, which is normally tipped away by brewers, but it achieves the same heat output.

I have to say, though, if you want to make this for your own consumption, be warned, it is extremely dangerous in concentrated doses above 80% and is not recommended by me, despite the fact most alcohol is sold at 40% spirit by volume, plus some places in the world do not allow alcohol production – so best check local by-laws where you are.


So, let’s give you a simple run-down on how it’s made.



Simple, really.

A sachet of bakers yeast

A couple of pounds of sugar (one kg)


One container that can be frozen and defrosted – like a 2-liter coke bottle, along with its cap, or a half-gallon lidded container, preferably plastic.

A small amount of cotton wool or a balloon.


This can take around two months to make as the yeast we are using is not the fast-fermenting type found nowadays from homebrew stores.

On the other hand, this time can be reduced considerably by using fast-acting yeast from many supermarkets.




Clean out the bottle – doesn’t have to be sterilized like wine-making bottles do for human consumption, but don’t use one with solids or obvious stains stuck to the inside of the bottle.

Now add the sachet of yeast and the sugar before adding the water which must be no more than 25 degrees centigrade otherwise it will kill off the yeast if it gets much higher. Twenty degrees is about right.

Pop the lid on once you have it around 3/4 full and give it a vigorous shake to mix it all thoroughly.

There’s no need for any sort of additives like wine-making demands – it’s just a simple three-item mix.

Slacken the top off after shaking it up so that air can escape from the inside as pressure builds, or take it off altogether and insert a plug of cotton-wool, or better still, remove the lid and install the balloon over the neck of the bottle to show you when gas is being produced as the balloon expands.

Obviously, you may need to adapt this arrangement as I am reciting it exactly as I produce alcohol with a plastic bottle.


That’s the ‘really technical’ bit done, so it’s just a matter of leaving it in a warm place for some time around two months – depending on temperature (20 to 25 degrees C).

No doubt you’ll be checking it as time goes on to see the gas bubbles rising and a sure sign when using a balloon is the balloon will expand after a few days.

If you stick a pin in the balloon near the top in just one place it will allow the carbon dioxide gas to escape and restrict any air from getting back into the fermenting mash, it forms a great fermentation trap.


If you use cotton wool, or perhaps the loosened lid of the bottle so that carbon dioxide escapes, the yeast reacting with the sugar produces a gas – carbon dioxide, which forms a covering over the liquid, and as this is heavier than air, it forms a barrier anyway, providing no very small vinegar flies can get into the liquid and kill the yeast off. These are usually around from June until around early October onwards where I live.

After some time, as I say, a couple of months if the temperature has remained constant, you will see no more bubbles rising to the surface. This means the yeast has done its job and has basically killed itself as the cells can no longer reproduce once their alcohol limit is reached.

With bakers yeast, you should now have around 9 or 10 % alcohol in your liquid – definitely 8%, regardless of the brand of yeast you have used.


All that is required now is to squeeze some gas from the bottle and screw the top on tightly.

Putting the top on is basically to avoid spillage when the bottle goes in the freezer and removing some gas is to allow the water to expand when it freezes without splitting the bottle.

In my case, I have to put the fermented liquid into smaller bottles with screw-on caps so they can remain upright in my freezer, otherwise, the frozen water can trap the separated alcohol in the bottle when you need to remove the alcohol as the alcohol is lighter than ice and rises above it.

I leave around an inch of air space before the cap is tightened on, and then squeeze the bottle to expel the air almost completely before tightening the top properly before popping them in the freezer.


Leave the bottle(s) in your freezer for a couple of days to make sure the water is frozen properly and then you can decant the alcohol into a different container, but you definitely need to make it an air-tight container, otherwise it will evaporate quite quickly as it will be almost pure alcohol.

Obviously, if it is freezing cold outside your home, just pop it outside with the bottles sealed in an upright position for a few days will do the same thing.

Provided the temperature is around 10 degrees below freezing for a couple of days, all will be well.

If you find there appears to be very little clear liquid in your bottles, do not be afraid of leaving them in the freezer a bit longer, as alcohol and water bond together very easily, so you need to break this bond by freezing the water thoroughly. You should be looking for around 8% in liquid form, and that is pure alcohol -100% proof spirit.


As a mention here: If you produce alcohol in this way, you will not be producing methyl alcohol as that needs fully natural products in the mash, like fruit, leaves, stalks, and other ex-living matter.

This alcohol is basically Ethyl alcohol – the safer sort that humans can cope with, providing they don’t have it concentrated or take in too much, made simply from sugar, water, and yeast.

If you intend to consume it yourself, you need to have everything spotlessly clean and sterilized before you begin the process otherwise you may be producing some methyl inadvertently, which is no good to man nor beast.


On no account must you try sipping this ethanol alcohol at 100% as it is a preservative and destroys living cells easily. Your tongue would immediately go numb as it tries to evaporate itself on your body heat and it is likely you’d have no sense at all or feelings in your mouth – and it could be permanent, never mind if it gets into your stomach.


That is a BIG  NO NO…

Peanut Shaped Stirling Double Cylinder Low-Temperature Difference Engine Model

The above fascinating Chinese coffee cup Stirling Engine with the black-painted arms rocking back and to when in motion, shown in the green link, is through Banggood with a price – freely delivered to the UK in 2 to 3 weeks, of just over 65 quid.

In the US it is offered for more or less the same price ($90 ish) and similar delivery time from Amazon, so you can guess where it’s coming from.


Sadly, this nice-looking piece is not on offer through Amazon in the UK, but if it was I expect it would be more expensive.


Just to give you the info…

The freezing point of water is 0 degrees C (32 degrees F).

The freezing point of alcohol is −114 degrees C (−173 degrees F).



Grandpa Joe.


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