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Making effective hand sanitizer

Hand sanitizer is a hot topic lately what with the novel corona virus becoming widespread. Recipes abound on the internet for homemade sanitizers using ingredients that have not been proven to truly be effective.

Many of these unreliable recipes use essential oils (tea tree is a popular choice) mixed into a base of aloe juice, and/or vodka, and/or witch hazel. There is no concrete evidence that a low-alcohol, essential-oil mixtures is an effective hand sanitizer.

Hand sanitizer if made with sufficient alcohol and used correctly and hand washing with soap and water, again if done correctly, are recommended and effective ways for controlling corona virus as well as other disease organisms. (1,2,8)

Soap makers normally measure ingredients by weight, but alcohol mixtures are one exception to this rule. Measure in fluid ounces (fl oz) or milliliters (mL) to get the correct ABV (alcohol by volume.)

You can measure by weight if you prefer, but you must include the lower density of alcohol when converting volumes into weights. I explain how to do this in the "Extra credit" section at the bottom of this article.

 

Alcohol at 60% ABV or higher is a proven sanitizer

The key for an effective hand sanitizer is keeping the percentage of alcohol in the sanitizer high enough. It must be at least 60% ABV.

The table below gives some examples of alcohol-containing ingredients that have been suggested for use in hand sanitizers. Some contain enough alcohol to be effective, but some do not.

The dilution ratios in the last column show how much of a high-proof alcohol to mix with non-alcoholic ingredients to get a final mixture that is 60% ABV.

Alcohol by volume Proof Example product Volume dilution ratio
15% ABV 30 proof Witch hazel (3) Not proven effective
40% ABV 80 proof Vodka Not proven effective
50% ABV 100 proof   Not proven effective
60% ABV 120 proof   Use full strength
75.5% ABV 151 proof Everclear (4) Dilute 79:21 (5)
91% ABV 182 proof Isopropyl alcohol Dilute 66:34 (5)
94.5-95.5% ABV 189-191 proof Everclear (4) Dilute 63:37 (5)

(3), (4), (5): See "Notes," below

 

What if I have alcohol with a different ABV?

If you want to use an alcohol with an ABV not listed above, here is how to calculate the correct volume dilution ratio needed to make a finished hand sanitizer at 60% ABV --

If you are using drinkable alcohol, convert "Proof" to ABV --

ABV = Proof / 2​

The volume of alcohol you should use to get 60% ABV in the sanitizer mixture --

Alcohol volume = 60 / ABV X 100​

If you want a different ABV in the finished sanitizer, replace the "60" in this formula with the desired final ABV percentage.

The volume of non-alcohol-based ingredients to add --

Non-alcohol volume = 100 - Alcohol volume​

 

Example 1-- I want to make 100 milliliters (mL) of 60% ABV sanitizer by diluting 160 proof alcohol.

ABV = 160 / 2 = 80%

Alcohol volume = 60 / 80 X 100 = 75 mL

Non-alcohol volume = 100 - 75 = 25 mL

In other words, to make 100 mL of hand sanitizer at 60% ABV, I should mix 75 mL of the 80% ABV alcohol with 25 mL of non-alcohol ingredients. In other words, the volume dilution ratio for 160 proof (80%) alcohol is 75:25.

If you want to measure in fluid ounces, substitute "fluid ounces" wherever you see "mL."

 

What are suitable non-alcohol ingredients?

I cannot stress this enough -- Essential oils have not been proven effective as hand sanitizers. Do not count on wishful thinking to protect you and your family. Alcohol in sufficient concentration is a proven hand sanitizer.

Use ingredients that will mix with the other ingredients in the sanitizer mixture. If an ingredient floats on top of the mixture, it is not suitable. Most carrier oils (sweet almond, jojoba, olive, etc.) will most likely not work in a hand sanitizer.

Small amounts of essential oils (EOs) such as tea tree and lavender can be included. Choose EOs that are generally recognized as safe on the skin. Also keep the total percentage of EOs at or below 3% by weight. These guidelines will increase the chances the EOs will stay mixed with the other ingredients and also ensure the EO content is reasonably safe to use on most people's skin.

Water alone will work fine as the main non-alcoholic ingredient, but it does not counteract the drying effect of alcohol on skin.

Many people use aloe juice or aloe gel instead of water to make a more skin-friendly formulation. Shake or blend the ingredients to get them to mix together.

Some sanitizers include glycerin (1.5% or more by weight) as a skin soothing humectant. Large amounts of glycerin can feel sticky on the skin.

Recipes I can recommend --

CBS News. Can't Get Your Hands on Hand Sanitizer? Make your own. https://www.cbsnews.com/news/hand-sanitizer-coronavirus-make-your-own/

Crunchy Betty. Easy Homemade Hand Sanitizer that Works on Three Levels. https://crunchybetty.com/easy-homemade-hand-sanitizer-that-works-on-three-levels/

ThoughtCo. Make Your Own Homemade Hand Sanitizer. https://www.thoughtco.com/make-your-own-homemade-hand-sanitizer-606145

Clean My Space. Make Your Own Hand Sanitizer. https://cleanmyspace.com/make-your-own-hand-sanitizer/

 

References and notes

(1) CBS News. Can't Get Your Hands on Hand Sanitizer? Make your own. https://www.cbsnews.com/news/hand-sanitizer-coronavirus-make-your-own/

(2) CDC. Show Me the Science: Handwashing. https://www.cdc.gov/handwashing/show-me-the-science.html

(3) Witch hazel can be used in your sanitizer recipe, but include it as one of the non-alcoholic ingredients. This approach will make the final ABV of your sanitizer a bit higher than 60%, but that is an error on the side of safety.

If you have decent math skills and Need To Know These Things, it is certainly possible to calculate the alcohol contributed by the witch hazel and factor that into your recipe.

(4) Everclear grain alcohol is sold in at least four different proofs, so read the label carefully before you buy.

For example, Everclear sold in Iowa must be no higher than 151 proof (75.5% ABV) by law. If I drive to Wisconsin, I can buy 189-191 proof (94.5-95% ABV).

(5) A 79:21 dilution ratio means you can mix 79 milliliters (or fluid ounces) of 75.5% ABV alcohol with 21 milliliters (or fluid ounces) of non-alcoholic ingredients to get a final mixture at 60% ABV. The dilution ratios given for the other alcohols are used in the same way.

(6) Engineering ToolBox. Density of Ethanol-Water Mixtures. https://www.engineeringtoolbox.com/ethanol-water-mixture-density-d_2162.html

(7) Wikipedia. Isopropyl alcohol. https://en.wikipedia.org/wiki/Isopropyl_alcohol

(8) ProPublica. You Might Be Buying a Hand Sanitizer That Won't Work for Coronavirus. https://www.propublica.org/article/coronavirus-hand-sanitizers-cdc-recommended-alcohol

 

Learn more

Mobjack Bay on the Soapmaking Forum. Hand Sanitizer discussion thread. Soapmaking Forum. https://www.soapmakingforum.com/threads/hand-sanitizer.78473

CDC. Show Me the Science: Hand Sanitizer. https://www.cdc.gov/handwashing/show-me-the-science-hand-sanitizer.html

CDC. Coronavirus disease. https://www.cdc.gov/coronavirus/2019-ncov/community/home/index.html

World Health Organization (WHO). WHO Recommended Hand Rub Formulations. https://www.who.int/gpsc/5may/Guide_to_Local_Production

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Extra credit. How to measure hand-sanitizer ingredients by weight rather than by volume.

The ingredients for hand sanitizer can be measured by weight, but you must account for the lower density of alcohol when you convert from a volume basis to a weight basis.

In the table below, the densities are in units of grams per cubic centimeter (g/cm3) at 20 C (68 F). These numbers are equivalent to specific gravity.

 

Ethyl alcohol Density, g/cm3 (6)
60-69% ABV 0.891
70-79% ABV 0.868
80-89% ABV 0.843
90-99% ABV 0.818
99.1-100% ABV 0.787

Isopropyl alcohol at 91-100% ABV has a density of 0.786 g/cm3 at 20C. (6,7)

 

If you are using drinkable ethyl alcohol, convert "Proof" to ABV --

ABV = Proof / 2​

The volume of alcohol to get 60% ABV in the sanitizer --

Alcohol volume = 60 / ABV X 100​

Volume can be in units of milliliters (mL) or fluid ounces (fl oz). Pick one or the other and stick with it. Do not mix units.

If you want a different ABV in the finished sanitizer, replace the "60" in this formula with the desired final ABV percentage.

Find the appropriate density for the alcohol you are using (see the density information given above).

Convert volume of alcohol to weight of alcohol --

Alcohol weight = Alcohol volume X Density

If the unit of volume you are using is milliliters, the weight will be grams (g). If the volume is fluid ounces, the weight will be in weight ounces (oz).

For the math geeks, combine the previous two equations into one and simplify the result --

Alcohol weight = 60 / ABV X 100​ X Density = 6000 / ABV X Density

The weight of non-alcohol water-based ingredients to add --

Non-alcohol weight = 100 - Alcohol weight

 

Example 2 -- I want to make 100 grams (g) of sanitizer at 60% ABV. I want to use 160 proof ethyl alcohol. Alcohol that is 80-89% ABV has a density of 0.843 from the table above. What is the dilution ratio in terms of weight?

ABV = 160 / 2 = 80%

Alcohol weight = 6000 / ABV X Density = 6000 / 80 X 0.843 ~= 63 g

Non-alcohol weight = 100 - Alcohol weight = 100 - 63 ~= 37 g

In other words, to make 100 grams of hand sanitizer at 60% ABV, mix 63 grams of 80% ABV ethyl alcohol with 37 grams of non-alcohol ingredients.

If you want to measure in weight ounces, substitute "weight ounces" wherever you see "g."

The weight dilution ratio for 160 proof (80%) ethyl alcohol is 63:37 to get a final sanitizer mixture at 60% ABV. Compare that to the volume dilution ratio of 75:25.

 

Example 3 -- I want to make 100 weight ounces (oz) of sanitizer using 91% isopropyl alcohol. Isopropyl alcohol has a density of 0.786 from the information given above. What is the dilution ratio in terms of weight?

Alcohol weight = 6000 / ABV X Density = 6000 / 91 X 0.786 ~= 52 oz

Non-alcohol weight = 100 - Alcohol weight = 100 - 52 ~= 48 oz

In other words, to make 100 oz of hand sanitizer with 91% isopropyl alcohol, mix 52 oz of the alcohol with 48 oz of non-alcohol ingredients.

If you want to measure in grams, substitute "gram" wherever you see "oz."

The weight dilution ratio for 91% isopropyl alcohol is 52:48 to get a final sanitizer mixture at 60% ABV. Compare that to the volume dilution ratio of 66:34.