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November 3, 2016

How to Make High Proof Watermelon Alcohol

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 internet is filled with tons of generic fuel alcohol recipes, however, this recipe is definitely an outlier. Once we started seeing watermelons in the grocery story and ripe melons in our garden this year, we didn't want to waste our time eating them. Instead, we turned them into something useful - high proof watermelon-derived fuel alcohol.

Below is a detailed procedure for making high proof watermelon alcohol. We actually tried this and it worked. FYI: We had a federal fuel alcohol permit when we tested this procedure and we were also in compliance with state requrements. We produced, stored, and used this alcohol in accordance with TTB requirements. We also kept and reported production logs in accordance with TTB fuel alcohol permit requirements.

Mashing Equipment

The first step is to make a sugary liquid with watermelon juice. The following items were needed:

  • Cutting board and a sharp knife

  • Blender

  • A fine cheesecloth

  • A couple of 5 gallon buckets

  • Large pot for mashing

  • Hot plate

  • A large paddle or spoon for stirring

  • Wort / immersion chiller (for cooling the mash)

  • A hose for siphoning

  • Thermometer

  • A glass carboy or food grade plastic bucket for fermentation

  • An airlock


  • 5 large watermelons

  • 2 pound of raisins

  • 4 pounds of cane sugar

  • 2 packets bread yeast (or wine yeast)

Mashing, Fermentation, and Distillation Procedure

  • First, we extracted the sweet, sweet watermelon juice from 5 large watermelons. We found that the easiest way to do this is to cut the Watermelon in half and then into quarters. Once quartered, we cut into slices and removed the rind. Next, we reduced it to chunks that will fit into a blender.

Slice Watermelon and Remove Rind

  • Next, we added chunks to the blender and obliterated the watermelon!

Add watermelon chunks to blender

  • We made sure not to over-blend. We shut down the blender as soon as the fruit had been liquefied. This will be filtered through a cheesecloth later and if the blended watermelon is too fine the pulp will go right through the strainer.

Lightly blend watermelon fruit

  • We dumped our watermelon puree through a cheesecloth installed in a food safe bucket. Nylon paint strainer bags are a good alternative to cheesecloth.

Pour watermelon puree through cheesecloth

  • We removed the cheesecloth containing pulp from the bucket and let some of the juice drip out.

  • Once the bag was a manageable size, we squeezed it to extract as much watermelon juice as possible.

  • After squeezing, we poured the strained watermelon juice into a large stainless steel mash-tun.

  • Add sugar to the juice and stir until it dissolves.

Add sugar to watermelon juice

  • Add 2 pounds of raisins.

Add raisins

  • We heated the strained watermelon juice, raisins, and sugar to 160F. This will kill most of the naturally occurring wild yeast and bacteria found in the watermelon juice.

  • After heating, we added cold water to reach a total volume of 5 gallons (if needed).

Add enough water to reach a total of 5 gallons

  • We cooled the mash to 70 degrees with a sterilized wort-chiller.

Use immersion chiller to cool watermelon mash

  • While the mash is cooling, we made a yeast starter using 2 cups of 120F water, 2 tsp of sugar, and 2 small packages of bread yeast.

Making a yeast starter using distillers, ale, or bread yeast

  • We took a starting gravity reading using a brix refractometer. We loaded the hydrometer by using a small dropper to remove a bit of juice from our mash pot.

Use a brix refractometer to calculate starting gravity

  • Ideally, the brix reading should be around 1.065, which will produce a starting alcohol of about 8%. If the reading is low add 100% pure cane sugar until the desired starting gravity has been reached.

Take a brix refractometer reading

  • Here's what a brix refractometer reading looks like

Brix refractometer results

  • We aerated the mash by transferring it between two sterilized food grade buckets. We poured it hard so lots of bubbles form on top of the liquid.

Aerate watermelon moonshine mash

  • Transfer the 70 degree mash to a sterilized fermentation vessel.

Transfer watermelon mash to carboy

  • Add the yeast starter to the fermenter.

Pitching yeast into brandy mash

  • Admire the beauty of the carboy full of watermelon juice.

Carboy full of watermelon juice

  • We added an airlock and fermented at 70F until finished. Read this article on fermentation to learn more about how to tell when fermentation is finished.

    • Our batch finished very quickly (in about 2 days) due to a high starting temp (which is not ideal).

Add an airlock to fermenter

    • Once the bubbles in the airlock slow down/stop take a gravity reading. Once the gravity reading does not change for 3 days or is 1.010 or below it is done. Our gravity finished just below 1.00, giving us a starting alcohol of about 8.5%, which is exactly where we want to be.

    Take a hydrometer reading to calculate alcohol %

    • After letting the wine settle for another 3-4 days (this will give the yeast time to settle to the bottom of the fermenter), we siphoned it into a 100% copper still.

    Siphon watermelon wash into copper still

    • We left the raisins, settled watermelon pulp, and as much yeast behind as possible.

    Leave raisins, watermelon pulp, and yeast behind

    • After that we distilled in a 5 gallon copper still.

    Again, it is illegal to distill alcohol without federal and state distillers or fuel alcohol permits.

    Additional Notes:

    As we've discussed in previous articles on alcohol yield, the final take from a distillation run will be highly dependent on the amount of sugar that is started with in the mash. Much of the sugar in this recipe will come directly from the watermelons. However, we've added some sugar as well.

    Why did we add sugar to this recipe? Well, fresh watermelon juice has an average brix of about 10. Some are higher. Some are lower. But that's a good average to use as a rule of thumb.

    The particular watermelons we used had a brix of around 8. About 20% lower than the average. We bought them from Walmart and they were grown in Mexico...and we got what we paid for! If we hadn't added sugar, our starting alcohol wouldn't be any more than about 4.5-5%. For the sake of maximizing our efforts we bumped that number up to 8%. This was just an experiment to see if it could be done, so we stopped there. One could add enough sugar to boost starting alcohol to 20% for fuel alcohol.

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