I’ve been seeing a lot of DIY hand sanitizer recipes lately, thanks to the novel coronavirus (covid-19). Unfortunately, a lot of the DIY recipes leave you with a product that is less than the CDC recommended 60% alcohol. I want to share why and how that happens, and give you a basic recipe to make your own hand sanitizer that follows the CDC guidelines.
First, it’s important to understand what your bottle of rubbing alcohol is: a bottle of 100% isopropyl alcohol and water. “Wait, my bottle says 70% rubbing alcohol!” I assure you, it’s still 100% alcohol mixed with water. Imagine an empty bottle, now put pure (100%) alcohol into the bottle, but only fill it halfway. Now fill the bottle the rest of the way with distilled water. You now have 50% rubbing alcohol because the solution (two or more things mixed together is a solution) is made up of 50% isopropyl alcohol and 50% water.
If you have 75% rubbing alcohol, you have a bottle that was filled 3/4 of the way with pure isopropyl alcohol and 1/4 of the way with distilled water. If you have 90% rubbing alcohol, you have a bottle that was filled 90% of the way with pure isopropyl alcohol and 10% with distilled water.
When you mix a solution, each individual component becomes diluted.
The Math
(The recipe is the next section down.)
There is a specific ratio that is used to find the concentrations or volumes in a solution:
It looks intimidating, but I’ll walk you through it!
The ‘C’ and ‘V’ in the equation stand for “component” and “volume.” The little numbers are called “subscripts.” The asterisk is a multiplication symbol. You would read the formula as “component one times volume one equals component two times volume two.”
The units, for our purposes, are percentages (%) and milliliters (mL). The percentages will be written in decimals, so 90% will be shown as 0.9 in the equation. I will translate the final numbers into cups, for anyone unfamiliar with mL.
We are trying to determine how much (volume) of the rubbing alcohol we need to make one cup (240mL) of hand sanitizer with 60% alcohol when it is completed. We will be starting with 90% rubbing alcohol. The equation will be setup like this:
First, multiply the right side of the equation (0.6 times 240). Then, divide both sides by 0.9.
Dividing the left side of the equal sign by 0.9 results in the 0.9 canceling itself out. All that remains to the left of the equal sign is the unknown volume. Dividing 144 by 0.9 gives us 160 mL.
The equation shows us that to make a 240mL solution that has 60% alcohol in it, we need 160mL of 90% rubbing alcohol. If the label on your rubbing alcohol says it’s less than 90%, then you need more of the rubbing alcohol. You can figure out exactly how much of your rubbing alcohol you need, by substituting the 0.9 in the equation with your rubbing alcohol percentage (if you have 70% rubbing alcohol, switch the 0.9 in the equation to 0.7; if you have 75% rubbing alcohol, switch the 0.9 in the equation to 0.75). If you have rubbing alcohol that is over 90%, then you can follow the same recipe, you will simply have a higher percentage of alcohol in the finished product.
If you want to use vodka (or another drinkable alcohol) as hand sanitizer, you’re going to have a difficult time meeting the 60% alcohol recommendation. To convert from “proof” to “percent alcohol” you divide by 200, so “100 proof” liquor is only 50% alcohol. Liquor that is 151 proof, is 75.5% alcohol. To get liquor that is 90% alcohol, you need to find 180 proof. Anything 180 proof or higher will work in the recipe below.
DIY Hand Sanitizer Recipe
Ingredients
- 160 mL (or 2/3 cups) of 90% rubbing alcohol*
- 80 mL (or 1/3 cups) of aloe vera gel
- a couple drops of essential oil, if preferred
Mix together all of the ingredients. Pour into a container that you can use to dispense the sanitizer, and you’re done! You may need to shake the container before each use, as the gel and alcohol may separate.
If you do not want that much aloe vera gel in your sanitizer, you can substitute some of the gel for distilled water. Make sure you do not add more than 80 mL (1/3 cups) to the rubbing alcohol! To make sure you’re not over-diluting the rubbing alcohol, put the desired amount of aloe into the measuring cup and then add water until you hit the 80 mL (1/3 cups) mark.
*Please see my note about non-rubbing alcohol being used to make hand sanitizer. The note is the last paragraph of “The Math” section.
Frequently washing your hands for 20 seconds with soap and water is the best option for keeping your hands clean and germ free, but you can’t always get to a sink. If you have access to soap and water, please use them!
During this unprecedented pandemic, please stay home to help protect everyone! There are many people that cannot stay home (essential workers, mainly), so they’re relying on those of us that can to help keep them safe!
People like me are also worth protecting! “Just the chronically ill and elderly will die” is a remarkably high amount of the population! Hypertension, asthma, diabetes, other chronic respiratory conditions, and other cardiac conditions all are “high risk” criteria. I have hypertension due to my dysautonomia, and I’ve had asthma since I was five years old. According to the American Heart Association, about 1/3 of the adults in the USA have high blood pressure (hypertension), and many may not know it. Please stay home to help protect people like me, and 1/3 of the adults in the USA!
Stay home, wash your hands, and stay a minimum of six feet away from other people if you absolutely have to go out (like, to get groceries). Stay safe!
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