Should I use 70 or 91 percent rubbing alcohol in a cleaner?

For a homemade glass or surface cleaner, either strength works, because the published recipes dilute it heavily: UF/IFAS's window cleaner uses 1/4 cup of rubbing alcohol in a mix that is mostly water and vinegar, and does not specify the strength. The difference is in the bottle. 91 percent isopropyl alcohol has less water, so it evaporates faster and is more flammable; its maker's SDS gives a flash point of 14 to 18°C (57 to 64°F), well below room temperature. 70 percent is the more common drugstore product and carries more water. Whichever you buy, never let it meet bleach. This page covers what alcohol does in a cleaner, flammability, surfaces and storage.

70 or 91 percent: the choice laid out

The flash point is the lowest temperature at which a liquid gives off enough vapor to ignite. At 14 to 18°C, 91 percent alcohol gives off flammable vapor at any normal indoor temperature. The lower and upper flammable limits on the same SDS are 2 and 12 percent vapor in air [1], which is why you never use it near a stove burner, pilot light, candle or cigarette, or spray it on a warm surface.

For a homemade recipe that does not say which strength, 70 percent is the sensible default: it is easy to find, it carries more water into storage, and once diluted in the recipe the difference in cleaning is small. Buy 91 percent if a source you are following asks for it.

What alcohol does in a cleaner

Isopropyl alcohol is a solvent. It dissolves light oily films, fingerprints and some sticky residues, and it evaporates quickly. Alliance Chemical's SDS gives a vapor pressure of about 33 mmHg at 20°C [1], high enough that a thin film dries in moments. In a glass cleaner that fast evaporation is the point: the liquid flashes off before it can dry into streaks.

The published recipe that uses it is the UF/IFAS window cleaner, quoted exactly:

"1/4 cup rubbing alcohol" "1/4 cup white vinegar" "1 tablespoon cornstarch" "2 cups warm water" "Combine all ingredients together in an empty spray bottle and shake well." [3]

The publication gives no strength for the alcohol. The full set of window recipes, with cloth and squeegee technique, is on the glass cleaner page.

What alcohol is not in this cleaner: a disinfectant. The drugstore bottle is labeled as a first aid antiseptic for skin [2], not as a surface disinfectant, and a homemade spray containing it can be described only by what it cleans. The difference between those labels, and what registered alcohol disinfectants require, is on the peroxide and alcohol page.

Never with bleach

UF/IFAS: "NEVER mix bleach with ammonia, vinegar, rubbing alcohol, or other household cleaners" [3]. North Carolina Cooperative Extension names bleach with rubbing alcohol among the combinations that make gases harmful to breathe [4], and the 91 percent SDS lists hypochlorites, the active in bleach, among the strong oxidizers alcohol is incompatible with [1]. What forms, and why hand sanitizer and alcohol wipes count as sources of alcohol, is on the bleach and rubbing alcohol page.

The same SDS lists peroxides among those strong oxidizers [1]. Keep alcohol and hydrogen peroxide in separate bottles and do not combine them in a homemade mix.

Surfaces and materials

• Plastic bottles: which resins hold alcohol, and how to test the bottle you will use, is on the resin compatibility page.
• Aluminum: the SDS says "Do not store or handle in aluminum equipment above 49°C (120°F)" [1], a handling rule for hot storage rather than a quick wipe.
• Wood finishes, painted surfaces, acrylic and some plastics: no source read for this page tests household alcohol on finishes. Solvents can soften or cloud some finishes and plastics, so test a hidden spot first, and follow the manufacturer's care sheet for anything you cannot refinish.

The surface table gathers what the sources say about each surface.

Flammability and other figures from the 91 percent SDS

H336 means vapor in quantity can cause drowsiness or dizziness. In a small, closed bathroom with a large bottle open, open a window or run the fan. If a child swallows any, call Poison Control at 1-800-222-1222 [5].

Storing rubbing alcohol and alcohol mixes

The SDS: "Store in a cool, dry, well-ventilated area away from heat, sparks, and open flame" [1]. At home that means:

• not above or beside the stove, water heater or furnace;
• tightly capped, since an open bottle loses strength and fills the room with vapor;
• away from bleach products;
• a homemade alcohol spray in a labeled bottle, never a food or drink container; NMSU says to store excess window cleaner in a glass jar with a tight-fitting lid [6].

For makers who sell a cleaner with alcohol

Alcohol brings two sets of rules. The federal hazardous substance rules use flash point bands to decide flammability warnings, explained on the is it hazardous page. And California and several other states cap the volatile organic compound (VOC) content of glass and general purpose cleaners, with the category limits and dates on the VOC limits page. Mailing an alcohol cleaner has its own rules, covered on the shipping page.

Making your glass cleaner

With the strength chosen and the bleach rule clear, go to the glass cleaner page for the UF/IFAS and NMSU recipes as published and the technique that keeps glass streak-free.

References

1. Alliance Chemical, Safety Data Sheet: Isopropyl Alcohol 91% USP Grade, revised October 21, 2026. https://docs.alliancechemical.com/sds/isopropyl-alcohol-91
2. U.S. FDA, OTC Monograph M003: First Aid Antiseptic Drug Products for Over-the-Counter Human Use, posted May 2, 2023. https://www.accessdata.fda.gov/drugsatfda_docs/omuf/monographs/OTC%20Monograph_M003-First%20Aid%20Antiseptic%20products%20for%20OTC%20Human%20Use.pdf
3. University of Florida IFAS Extension, Griffin and Cantrell, Homemade Household Cleaners (FCS3319), Release Date October 7, 2025. https://ask.ifas.ufl.edu/publication/FY1449
4. N.C. Cooperative Extension, Yancey County Center, Maness, Health Risks of Mixing Household Cleaners, November 1, 2024. https://yancey.ces.ncsu.edu/2024/11/dontmix/
5. Poison Control (National Capital Poison Center), Poison Statistics: National Data 2024. https://www.poison.org/poison-statistics
6. New Mexico State University Cooperative Extension, Griffiths and Koukel, Green Alternatives to Toxic Household Products and Hazardous Waste (G-313), revised February 2019. https://pubs.nmsu.edu/_g/G313/index.html