What is washing soda, and how is it different from baking soda?
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Washing soda is sodium carbonate, a close chemical cousin of baking soda (sodium bicarbonate) and a much stronger alkali. Arm & Hammer's washing soda measures pH 11.4 against 8.2 for a 1 percent baking soda solution, more than three pH steps apart, and its maker classifies it as causing serious eye irritation where baking soda carries no hazard class at all. That strength is why washing soda cuts heavy grease and softens laundry water, and why it needs gloves, belongs in spray bottles only at the small amounts recipes give, and leaves a white film when used too strong. This page compares the two, then covers uses, hazards, mixing and storage.
Washing soda and baking soda side by side
| Baking soda | Washing soda | |
|---|---|---|
| Chemical | Sodium bicarbonate | Sodium carbonate |
| pH on the maker's SDS | 8.2 (1% solution) [1] | 11.4 (concentration not stated) [2] |
| Hazard class on the maker's SDS | Not hazardous under OSHA's standard (2009 sheet) [1] | Eye irritation Category 2A, H319 "Causes serious eye irritation," signal word Warning (2015 sheet) [2] |
| Oral LD50 (rat) | 7.3 g/kg [1] | 4,090 mg/kg [2] |
| Main cleaning job | Mild abrasive, deodorizer, gentle wash [3] | "To cut heavy grease" [3]; laundry booster |
| Reaction with acid | Gives off carbon dioxide [1] | Gives off carbon dioxide [2] |
The two pH figures were not measured at the same stated concentration, so read the gap as a ranking rather than an exact ratio. The practical risk is confusion: both are white powders, sold under the same brand. Keep washing soda in its own box, clearly marked, and away from the kitchen.
What washing soda is used for
Heavy grease
NMSU lists washing soda "to cut heavy grease" [3] and allows it as an alternative to baking soda in its powdered cleaner [3]. University of Georgia Extension's floor cleaner for greasy, no-wax floors combines 1 cup white vinegar, 1/4 cup washing soda and 1 tablespoon liquid soap in 2 gallons of hot water, with the instruction to stir well "to dissolve the washing soda" [4]. The vinegar and washing soda in that recipe react with each other, a point taken up on the combinations page; the recipe is quoted as published on the floor cleaners page.
Laundry
Washing soda is a builder: it ties up the calcium and magnesium in hard water so soap and detergent can work. UF/IFAS uses it with borax and bar soap in its homemade laundry powder and liquid [5]. Those recipes, with their doses, live on the homemade laundry detergent page, and how hardness affects your wash is on the hard water page.
In small amounts in an all-purpose spray
UGA's All-Purpose Cleaner uses only 1/2 teaspoon of washing soda in 2 cups of hot water, with vinegar and liquid soap [4]. The source does not explain the amount, but keeping it that small also keeps residue and sprayer trouble down.
White film and clogged sprayers
Whatever dissolves in a cleaner stays behind when the water evaporates, and with washing soda that residue is a white, chalky powder: crust in a trigger nozzle, or a haze on glass, dark counters and floors when a strong solution dries. Hard water adds to it, because carbonate and calcium together make the chalky mineral of limescale, and the Church & Dwight sheet lists lime among the materials washing soda is incompatible with [2]. Use washing soda only at the small amounts a published recipe gives, dissolve it fully in the hot water the recipe calls for, and rinse surfaces after cleaning. The causes of sprayer clogs, and how to clear a trigger, are on the streaks, clogs and film page.
Skin and eyes
At pH 11.4, washing soda is hard on skin, and its SDS classifies it as an eye irritant [2]. Wear waterproof gloves for scrubbing with a washing soda solution, and eye protection when you pour or measure powder that can puff into the air. The protecting yourself page covers gloves by task.
If it gets on you, the manufacturer's first aid is:
- Eyes: "Rinse cautiously with water for at least 15 minutes," removing contact lenses if easy, and get medical attention [2].
- Skin: remove contaminated clothing and drench the area with water for at least 15 minutes [2].
- Swallowed: rinse the mouth, do not induce vomiting, and get medical attention [2]. Call Poison Control at 1-800-222-1222 [6].
Surfaces to keep washing soda off
No extension or trade source read for this page publishes a surface list for washing soda specifically. What the sources do establish is that it is a strong alkali [2], and the general cautions for alkaline cleaners apply: rinse after use, test on a hidden spot first on painted, varnished or waxed wood, and follow the maker's care sheet for aluminum, natural stone and any finish you cannot replace. The surface table sets out what is known surface by surface.
What not to mix it with
- Acids (vinegar, citric acid, lemon juice): "Reacts with acid to form: Carbon Dioxide" [2]. The result is neither the acid nor the alkali you wanted.
- Bleach and every other cleaner: CDC's rule is never to mix household bleach with any other cleaner [7].
- Lime: listed as incompatible on the SDS [2]. This matters in garages and garden sheds where builders' lime is stored.
Storing washing soda
The Church & Dwight sheet says: "Keep container closed when not in use. Store in a dry, cool place" [2]. It also lists temperatures above 228°F (109°C), direct sunlight and incompatible materials as conditions to avoid [2]. Keep it:
- in the original box or a sealed, labeled container, never one that held food;
- away from baking soda and kitchen ingredients;
- dry, since damp washing soda cakes into lumps;
- out of reach of children, like every cleaning product. Household cleaning substances were the most common substance category in poison center exposures for children 5 and under in 2024 [6].
Choosing between the sodas for your job
Use baking soda when you want to scrub or deodorize without much alkali. Use washing soda when grease or laundry needs real alkalinity and you can wear gloves. If a recipe calls for borax alongside washing soda, the borax page explains its hazard classification and the alternatives, and if your washing soda spray has already clogged, go to the streaks, clogs and film page.
References
- Church & Dwight Co., Inc., Material Safety Data Sheet: Sodium Bicarbonate (Baking Soda), MSDS-960, issued January 20, 2009. https://www.physics.purdue.edu/primelab/safety/MSDS/Retired%20SDS%20and%20MSDS/2017%20removed%20safety%20sheets/MSDS%20updated%20to%20SDS/baking%20soda%20%20-%20Arm%20and%20Hammer.pdf
- Church & Dwight Co., Inc., Safety Data Sheet: Arm & Hammer Super Washing Soda, version 1.0, October 2, 2015. https://uwaterloo.ca/fine-arts/sites/default/files/uploads/documents/arm_and_hammer_washing_soda_10-02-2015.pdf
- 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
- University of Georgia Cooperative Extension (Pamela R. Turner and Sharon M. S. Gibson), *Green Cleaning: Recipes for a Healthy Home*, HACE-E-73-1 (Green Clean Booklet), revised October 2018. https://site.extension.uga.edu/greenway/files/2024/09/10.18_Green-Clean-Booklet_update.pdf
- University of Florida IFAS Extension, Griffin and Cantrell, Homemade Household Cleaners (FCS3319), Release Date October 7, 2025. https://ask.ifas.ufl.edu/publication/FY1449
- Poison Control (National Capital Poison Center), Poison Statistics: National Data 2024. https://www.poison.org/poison-statistics
- Centers for Disease Control and Prevention, Cleaning and Disinfecting with Bleach, last reviewed April 24, 2024. https://www.cdc.gov/hygiene/about/cleaning-and-disinfecting-with-bleach.html
