How to: The science of making your own hand sanitizer

Amidst the coronavirus breakout, everyone is getting in on the hand sanitizer craze. But if your local pharmacy has run out of pre-made hand gel, do not despair — you can make your own.

And it is easy.

With the guidance and four scientists, here’s how Inverse made our own sanitizer, and how you can too.

Input: This web app monitors the spread of the coronavirus

What is in hand sanitizer?

Hand sanitizer is made from three essential ingredients:

1. Water
2. Alcohol above 60 percent
3. Glycerin (or another gel)

“Products like “Purell” are essentially 62 percent ethanol (regular alcohol) mixed in a gel,” Stephen Morse, professor at Columbia University, tells Inverse.

“The purpose of the gel is to make the product easier to carry around, so people have it when they need it, slow the evaporation of the alcohol so it stays on the skin long enough to work well, and to make it gentler on the hands," Morse says.

"Vitamin E is often included in the commercial products,” he adds. Vitamin E is known to boost skin health, but it isn't necessary. All you need are alcohol above 60 percent, glycerin gel

“It’s not magic, just convenient,” Morse says.

“Based on past testing, and what we know about this virus, most normal household cleansers, detergents, disinfectants, also work," as cleansers, he says.

Is there a recipe for hand sanitizer?

Here is how to do it, according to Didier Pittet, an expert in infectious disease control at the World Health Organization and one of the writers of the WHO formulation — a recipe for hand sanitizer.

Formulation I

To produce final concentrations of ethanol 80% v/v, glycerol 1.45% v/v, hydrogen peroxide (H₂O₂) 0.125% v/v.

Pour into a 1000 ml graduated flask:

ethanol 96% v/v, 833.3 ml

H₂O₂ 3%, 41.7 ml

glycerol 98%,14.5 ml

Top up the flask to 1000 ml with distilled water or water that has been boiled and cooled; shake the flask gently to mix the content.

Formulation II:

To produce final concentrations of isopropyl alcohol 75% v/v, glycerol 1.45% v/v, hydrogen peroxide 0.125% v/v:

Pour into a 1000 ml graduated flask:

isopropyl alcohol (with a purity of 99.8%), 751.5 ml

H₂O₂ 3%, 41.7 ml

glycerol 98%, 14.5 ml

Top up the flask to 1000 ml with distilled water or water that has been boiled and cooled; shake the flask gently to mix the content.

“In developing countries, we actually recommend using glycerin, which is a very simple material and of course mixing alcohol, and a little bit of water," he tells Inverse.

"To make your own hand sanitizer, make sure you pay attention to the percent alcohol present."

The WHO formulation is available online, but he notes that it is designed for healthcare worked to make their own hand sanitizer in locations where there is a shortage.

“Currently, drugstores and pharmacies in Switzerland are producing those alcohol rubs because where there is a shortage of alcohol-based hand rub,” Pittet says.

This is not new: Healthcare workers have been doing the same thing in places where access to hand sanitizer is scant for years — including in Africa, to help protect against Ebola exposure, he says.

But before you go ahead and make your own, Pittet strongly suggests you do not try this at home yourselves.

“I will certainly not do it by myself in my kitchen," he tells Inverse. The reason? You will probably get the recipe wrong.

"You need to calculate the amounts that you need to use,” Pittet says. “You need to check, eventually, the quality of what you have done. So what I would really recommend is to go to a pharmacy where they can do it. It's a preparation and they will do it.”

How you make it matters

Thankfully, some of the experts Inverse spoke to are less pessimistic about your chances of getting it right.

“Making your own hand sanitizer is fine as long as you can be sure that the isopropyl alcohol or ethanol concentration is at least 60 percent, per CDC guidelines,” Tanya Crum, professor the Benedectine University in Chicago, tells Inverse.

But "it would be difficult to test the hand sanitizer at home in terms of the ability to kill viruses.”

Crum sent out a notice to her students via email, explaining how to make hand sanitizer on campus:

“To make your own hand sanitizer, make sure you pay attention to the percent alcohol present," she advises.

“If you fill a bottle about two-thirds of the way with 90-91 percent alcohol and fill the remaining third with aloe, you will make sanitizer that is about 60 percent alcohol. To make it more concentrated, add up to 8 parts 91 percent alcohol and 2 parts aloe," she says.

And if nothing else, 70 percent rubbing alcohol should also work just fine, undiluted in a spray bottle, Crum says.

PSA: Do not use vodka to make hand sanitizer.

“The strongest vodka I’ve seen is 100 proof, or 50 percent ethanol," Morse says. That is just not strong enough to kill bacteria or viruses like COVID-19.

Inverse went to a nearby liquor store on a quest for vodka containing over 60 percent alcohol, and were told that there is basically no such thing. The highest percentage vodka in the shop was a 50 percent ethanol alcohol vodka, produced by Smirnoff.

"I would not use vodka to make hand sanitizer at home," Crum says.

On Thursday, Tito’s Vodka even took to social media to beg their customers to not buy vodka to make sanitizer. Their vodka only contains 40 percent alcohol and that isn’t enough to meet the alcohol threshold.

Inverse makes hand sanitizer

Inverse bought the ingredients to make our own at a local pharmacy — when we visited, there was no commercial hand sanitizer available for sale.

But there was rubbing alcohol and pure glycerin (although Helmenstine says you can also use aloe vera gel).

We bought 70 percent ethyl alcohol.

Together with the glycerin, it cost $11.49 for both ingredients.

Prep your ingredients

First, find yourself a measuring beaker.

For our mix to have at least 60 percent alcohol, we could not dilute the rubbing alcohol very much.

The right proportions to make a hand sanitizer that actually fends off germs involves 90ml alcohol and 10ml glycerin, approximately.

Second, measure your three parts alcohol.

Then, measure out one part glycerin.

Mix it all together, letting the glycerine sink to the bottom.

You can also add essential oils, or a touch of something scented if you want to get rid of the strong alcohol smell.

Time to test

As we mentioned before, this DIY hand sanitizer solution cannot be readily tested with the equipment needed to know if it will truly work to kill bacteria and viruses just like the commercial product.

But you can give it a go on your skin. And it is... alcohol-y.

Thankfully the scent of pure ethanol quickly evaporates. The glycerin plays a vital role, moisturizing your hands and leaving them feeling so fresh and so clean.

Our solution was less viscous than commercial gel hand sanitizers, but that's just because we only had 70 percent alcohol to work with, and didn't want to dilute it too much.

The more alcoholic your rubbing alcohol is (aim for pure 100% if you can!) the more glycerin you can add, allowing for a more creamy or gel-like product.

What are the risks of making your own hand sanitizer?

“The CDC recently asked people to not make homemade hand sanitizer because there is so much misinformation online about ingredients,” Anne Helmenstine, a chemist and science advisor who has recently been in the limelight for her articles about homemade hand sanitizer, tells Inverse.

“But, I've been contacted by readers in Italy who are truly desperate for alternatives to commercial products,” she says. “I don't recommend making hand sanitizer unless you can't get the commercial product or are sensitive to an ingredient. If you can't buy hand sanitizer, then it's certainly fine to make it.”

She explains that, when making products at home, you need to be comfortable with the uncertainty that brings — you can mix it up, but you can't test how well it works in your kitchen sink.

“The best they can do is to combine ingredients in a way that has been tested by professionals,” she says.

“The biggest risk is not using enough alcohol or using the wrong type of alcohol,” she says.

“If homemade hand sanitizer doesn't have enough alcohol, then it confers a false sense of security in users.”

According to Helmenstine, these are some of the things to keep in mind:

• Ethanol is the best alcohol for hand sanitizer, because it's safe enough for human consumption.
• Isopropyl alcohol is also safe for skin use, but should not be ingested.
• Other types of alcohol are highly poisonous, such as methanol.
• Some online recipes also call for essential oils. When used incorrectly, essential oils are either ineffective or even dangerous.

“I think people can make a safe and effective hand sanitizer, but only if they understand the product must contain at least 60 percent ethanol (closer to 90 percent is better) and must be used correctly,” Helmenstine says.

Our verdict?

We cannot say if the product we created will offer any protection from COVID-19 or another virus or harmful bacteria. That would require rigorous, lab-based testing.

We can say this: You can manage to make a hand sanitizer-like gel in your home (or workplace) with ease. All you need is the recipe, the vital ingredients, measuring ware, and a mixing cup. And the experts agree: Getting all of that right makes a huge difference to your chances of success.

But before you go ahead and look for rubbing alcohol, consider this: Washing your hands with soap and warm water for 20 seconds in the correct way is just as effective at helping to prevent the spread of COVID-19. We talked to Pittet about why hand washing is the true first-line defense against the coronavirus, and the best ways to do it. Perhaps try that first, and leave the hand sanitizer to the experts.