How and why can homemade alcohol, like moonshine or rakija, make you go blind?
In: Biology
When yeast ferments sugars it mostly produces ethanol, which is what makes you drunk and is (mostly) safe for human consumption. However there are a lot of other things that can potentially be made as well, and with distilled liquors the big problem you run into is methanol, which is toxic and can make you go blind. When you distil a liquid you heat it up and use the differences in boiling point of the different liquids to separate them. Methanol has a lower boiling point than ethanol or water, so when you start distilling your homemade liquor the very first thing that will come out of the still is fairly concentrated methanol. Which is bad.
Experienced and professional alcohol distillers know to discard the first output, but inexperienced home brewers might not know, and accidentally drink or sell straight poison.
Improper distillation can lead to methanol being present in the hooch which can [destroy the optic nerve](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8731680/)
On occasion it is spiked with cheap methanol vs. ethanol; methanol is real bad for well everything!
Also methanol will likely be present in if not accounted for in home brewing of spirits.
A by-product of fermentation is methanol. It vaporizes at lower temp than ethanol. So when you distill your mash to get alcohol you start distilling methanol first, then distill ethanol (the alcohol you want).
Sometimes moonshiners don’t know about this and keep the entire distillation run. So the first few jugs they fill with “booze” are high in methanol. One of the long term effects of methanol poisoning (if you survive the short-term) is blindness.
If it’s made correctly, it won’t. Distilled alcohol is made in two main phases: fermentation and distillation. Fermentation results in different types of alcohol all mixed together in some percentage, usually between 5 and 20 percent. At that point there is actually different types of alcohol in it. Ethanol, the (relatively) safe stuff is what you want, but there are other alcohols, usually referred to [‘higher alcohols or ‘fusel oils’] (https://en.wikipedia.org/wiki/Fusel_alcohol), which is the dangerous stuff.
When the distillation is done, the different alcohols boil out at different temperatures, so what needs to be done is that the ‘good’ alcohol (ethanol) is kept and the ‘bad’ (fusel oils) is discarded.
However, amateurs may or may not really know what they’re doing, and/or have the correct equipment to make sure what they produce has only ethanol in it. So, if there’s too much of the higher alcohols, then the result can be dangerous if you drink too much of it.
Distilling at too low a temperature will leave behind byproducts (especially methanol) that are pretty bad for you.
Back in the day, it was somewhat common to use freeze distillation, where you leave a lower-alcohol product like cider out in the cold for several weeks, removing the ice each day. This drives up the alcohol concentration by removing water, but it leaves *all* these nasty byproducts behind in very high concentrations.
In high school biology they teach you that Yeast + Sugar = Ethanol + CO2 + heat. The reality of the situation is that when you are fermenting a mash that’s made of complex organic matter that in addition to ethanol there are small amounts of another alcohol called methanol (aka wood alcohol).
Methanol is used in products like antifreeze and varnish. It’s also toxic to humans in high concentrations. That’s what causes blindness. It also causes liver, pancreas, and kidney problems.
Experienced and ethical distillers anticipate this methanol when they distill a mash and they have adapted the process of distillation to remove methanol from their product. Home distillers might not have this expertise and end up concentrating the trace amounts of methanol in their product.
Bad info being provided here, but somewhat understandably so, given the years of misinformation being spread. The gist of it is if it’s safe to drink prior to distillation, it’s safe to drink after distillation. That isn’t to say you’ll be headache free or feel wonderful, but the fear of blindness related to methanol is bunk regarding typical distillation, whether commercial or at home.
The misinformation basically started when spirits were purposely contaminated with added methanol to instigate fear, curbing distillation in support of prohibition. There’s more to the subject. For anyone interested, I’d suggest reading the sticky post at the top of r/firewater.
Like many things, alcohol may be entertaining; but ultimately it’s a calibrated poison. If you don’t have the knowledge to calibrate that properly you could end up harming yourself by failing to remove the “bad parts,” (methanol as other commenters have mentioned). It’s a matter of experience
As an example, think about cooking with wine. When you do that you need to reduce it, and as a short hand many recipes say “reduce by half.” What you’re actually doing here is removing the “bad part” (alcohol), just like when you’re manufacturing alcohol, so you’re left with the “good part” (flavor) available in the wine.
For home cooks it can be simplified to “reduce by half” because the stakes are low: worst case scenario you fuck up the flavor of your bourguignon, but that’s about it. If you don’t reduce it properly, the food might not taste as good, or on some small scale you might feel the effects of the alcohol.
For something like actually making alcohol, the stakes are far higher (e.g. blindness and death). Which is why playing with it absent the requisite experience is generally a bad idea; and why the warnings against doing so are so emphatic.
To make drinkable ethanol booze, you ferment stuff and then distill out the ethanol. But fermenting doesn’t just produce ethanol. It can produce a lot of other chemicals including methanol, especially from fruit stock high in pectin. Methanol is poisonous, it will blind you.
To avoid this you stick to stocks that don’t have pectin or have low pectin, and you should use fractional distillation and make cuts. You can do this with pot distillation, but you’ll need to throw out a lot more to be safe. Basically, you get four parts as you raise the temperature. The problem is there is no clear line of you get X, temp goes up you get Y. It blends together, so there are stages with safety margins.
* Foreshot: Nearly pure poison, discarded.
* Head: Ethanol with some methanol and other bad tasting stuff, can save and distill it again.
* Heart: Almost pure ethanol, this is what you drink.
* Tail: Ethanol with some bad tasting stuff, can save and distill it again.
There is a chemical check you can do to ensure there’s no methanol in your alcohol. Licensed commercial producers of alcohol do all of this and more, so you can trust that it won’t blind you. You can’t trust that some stranger making bathtub gin did all of this, so you may end up blind.
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