The first 5% of your run will consist of the foreshots. Foreshots contain methanol which is an extremely volatile and toxic alcohol. As a standard practice, always throw out the first 250 ml per 5 gallons as this part of your run will consist of these foreshots.
WARNING* Do not consume this part of your run!
Be sure to isolate the foreshots thoroughly and throw them out. Consuming this alcohol, known as methanol can cause an array of issues with your health, including blindness.
The next 30% percent of your tequila run is known as the ‘heads.’ Similar to the foreshots, the heads of your run are filled with volatile alcohols that you should not consume. One of the staples of the heads is a particularly volatile alcohol known as acetone.
Acetone is fairly easy to identify, because of its distinct, solvent-like smell. Drinking the heads from your tequila run won’t make you blind but they will leave you with the worst hangover of your life.
Like your foreshots, you’ll want to isolate these and throw them out.
*Note a great way of isolating both the foreshots and heads in your run is to bring your still to around 168 °F and keep it there for around 10 minutes. The alcohol produced during this duration will consist of only foreshots and heads. Once the condenser stops producing at 168 °F, you’ll know that you’ve collected all of the foreshots and heads of the run.
The next 30% of your run will be the sweet spot of your tequila run. This portion of your distillate is known as the ‘hearts’ and it’s where you’ll produce a consumable spirit. You’ll want to raise the temperature of your still to 175 °F to 180 °F range to start collecting this portion of your distillate.
At this stage, you’ll notice the solvent smell of acetone taper off and be replaced by a sweet-smelling ethanol. A distiller with lots of experience really shines during this stage of the distillation process. Maximizing high-quality hearts comes with practice. You will recognize the ‘hearts’ portion of your spirit by the sweet and neutral flavor. You should only taste a bit of the distillate on your finger. Not time to break out the shot glasses just yet.
By accurately identifying where the acetone stops and the ethanol begins, you can really maximize the amount of high-quality tequila you’ll be able to produce. The main things to recognize here are the fading of the solvent smell of acetone and the sweet/smooth taste of ethanol getting stronger.
The last 35% of your tequila run will be the ‘tails’ portion. You can recognize the tails by the sight, smell, and taste. You should see an oily film start to collect on the top of the tequila distillate and be able to smell/taste a type of burnt flavor. The tails contain protein and carbohydrates from the wash that you don’t want in your final product.
You should hold on to your tails because you can actually re-run them as their own wash in a future run to pull out a bit more product.