Understanding the Proof and Amount of Alcohol Needed for Effective Hand Sanitizer

When crafting hand sanitizers, one common confusion is the role of alcohol proof and the necessary amount of alcohol. This article clarifies these points and discusses the best practices recommended by health organizations, ensuring that the homemade hand sanitizer is effective and safe to use.

What Is 'Proof' and Why Does It Matter?

'Proof' refers to the standard measure of an alcoholic beverage's strength. It is twice the percentage of alcohol by volume (ABV) in the solution. For instance, 80-proof alcohol contains 40% alcohol by volume.

While proof can give a general idea of the concentration, it is not the only factor for hand sanitizer effectiveness. What truly matters is the presence and percentage of the alcohol in the solution. The optimum alcohol concentration for an effective hand sanitizer is higher than that of common alcoholic beverages.

Minimum Alcohol Concentrations

To be effective, a hand sanitizer must contain at least 60% ethyl alcohol (also known as ethanol) or 70% isopropyl alcohol (also known as isopropanol).

Using Ethyl Alcohol (Ethanol)

For ethyl alcohol, at least 60% of the hand sanitizer should be ethanol. This concentration is often sufficient and is the primary alcohol used in many commercial hand sanitizers. Ethyl alcohol is more reactive and effective in breaking down the viral and bacterial cell walls.

Using Isopropyl Alcohol (Isopropanol)

For isopropyl alcohol, the content must be at least 70%. This higher concentration is necessary because isopropanol is generally less reactive than ethyl alcohol. Combining isopropyl alcohol with 0.125% hydrogen peroxide can enhance its effectiveness slightly.

It is important to note that using alcohol with a proof higher than necessary, such as 100-proof vodka, can be less effective than a properly concentrated solution. According to some testing, a 60% solution can be more effective than a 100% proof alcohol solution due to its better dispersion and effectiveness in breaking down the pathogens.

WHO Guidelines and Pharmaceutical Grade Products

The World Health Organization (WHO) recommends the use of pharmaceutical grade products when making hand sanitizer. This means avoiding the use of 'technical grade' ingredients, as they may not meet the same purity and quality standards.

Pharmaceutical grade alcohols are more refined and free from impurities, ensuring that the hand sanitizer is both safe and effective. Technical grade alcohols, on the other hand, may contain various impurities that can affect the overall effectiveness and safety.

Additional Considerations

While 60% ethyl alcohol or 70% isopropyl alcohol is the bare minimum concentration, adding extra water can help to reduce the overall viscosity of the solution, making it easier to apply. However, it is important to maintain the minimum alcohol concentration to ensure efficacy.

For lower concentrations, such as those with 50% alcohol, the contact time required for the sanitizer to be effective increases proportionally. This means that while a lower concentration can still be effective, users must prolong their application time to achieve the same level of germ-killing as a higher concentration solution.

Conclusion

Understanding the proof and the amount of alcohol needed for effective hand sanitizer is crucial for creating a product that truly works. Using 60% ethyl alcohol or 70% isopropyl alcohol is the recommended practice, and pharmaceutical grade products should be prioritized to ensure safety and effectiveness. By following these guidelines, you can create a hand sanitizer that helps protect against pathogens without overusing resources.