Why Is 70% the Most Effective Concentration of Denatured Ethanol for Disinfection?

Denatured ethanol, particularly in solutions between 60% and 90% alcohol with 10 – 40% purified water, is rapidly antimicrobial against bacteria, fungi, and viruses. Once alcohol concentrations drop below 50%, usefulness for disinfection drops sharply. Notably, higher concentrations of alcohol don’t generate more desirable bactericidal, virucidal, or fungicidal properties.

The presence of water is a crucial factor in destroying or inhibiting the growth of pathogenic microorganisms with denatured ethanol. Water acts as a catalyst and plays a key role in denaturing the proteins of vegetative cell membranes.  70% denatured alcohol penetrate the cell wall more completely which permeates the entire cell, coagulates all proteins, and therefore the microorganism dies. Extra water content slows evaporation, therefore increasing surface contact time and enhancing effectiveness. Denatured alcohol concentrations over 91% coagulate proteins instantly. Consequently, a protective layer is created which protects other proteins from further coagulation.

Solutions > 91% denatured alcohol do kill bacteria, but sometimes require longer contact times for disinfection, and enable spores to lie in a dormant state without being killed. In this analysis, a 50% denatured alcohol solution kills Staphylococcus Aureus in less than 10 seconds (pg. 238), yet a 90% solution with a contact time of over two hours is ineffective. Some disinfectants will kill spores, which are classified as chemical sterilants. So why do higher alcohol solutions yield fewer results for bactericidal and antimicrobial outcomes?

70% Denatured Ethanol

70% denatured alcohol upholds key requirements for use as a bactericidal in clean rooms or medical facilities, but also for general purposes. 70% denatured ethanol mixed with 30% water solutions produce less vapour and odour, therefore reducing risks of toxic fumes or combustion. When denatured alcohol reacts with air, light, and oxygen, it forms unstable peroxides which increase the likeliness of explosion, especially when heated with aluminium.

70% denatured ethanol is not only less flammable but also offers a more economical price point for general wipe down and large-surface disinfection. Likewise, high-moisture alcohols evaporate slower and increase contact time without becoming immediately dry.


  • 70% Denatured Ethanol
  • Glycerine – for extra soft skin care
  • Purified Water
  • Aroma Composition – perfume the treated area

If you need more information about ethanol and its use as disinfectant, please feel free to contact us.