Borax vs Washing Soda: Which One Does Your Laundry Actually Need?

So you're making your own laundry detergent — great, you've already read our cost comparison and maybe even the recipe. Then you hit the laundry aisle and find two very similar white boxes: 20 Mule Team Borax and Arm & Hammer Super Washing Soda. Similar prices, similar packaging, similar-sounding names. Here's the thing nobody tells you at the shelf: they're not the same chemical, they do different jobs, and you probably don't need to understand chemistry to use them right — but knowing which one matters more will save you money and an ingredient.

Short version:

• The difference: borax is moderately alkaline (pH ~9.5); washing soda is strongly alkaline (pH ~11) — a much more powerful cleaner.
• In the laundry: borax buffers pH, brightens whites, and works best in hot water; washing soda cuts grease, softens hard water, and works at any temperature.
• Safety: both can irritate skin — wear gloves when handling, and keep both away from kids and pets (borax is toxic if swallowed).
• Do you need both? Not necessarily. If you had to pick one for laundry, washing soda is the one doing the heavier lifting — and there's a borax-free recipe option below.

The Short Answer

If your laundry life involves mostly warm and cold washes, kid-level stains, and a regular supermarket budget, washing soda is the ingredient that matters more. It's the stronger cleaner, it softens hard water, and it works at any wash temperature. Borax is a genuine helper — it brightens whites and stabilizes the wash water — but it performs best in hot water, and many modern households barely wash hot anymore.

That doesn't make borax useless; it makes it optional. Plenty of households use both because the classic recipe calls for both, and there's nothing wrong with that. But if you're standing in the aisle deciding whether to buy one box or two, or if you have small kids and one fewer "keep away from children" product appeals to you, washing soda alone with your grated bar soap makes a perfectly good borax-free detergent. The cost difference is a wash — both boxes are cheap — so decide on the merits, not the price.

What Each One Actually Is

No chemistry degree needed, but a little context helps the rest of the article make sense:

• Borax (sodium tetraborate) is a naturally occurring mineral — mined, mostly from dry lake beds in California and Turkey. In water it makes a mildly alkaline solution, pH around 9.5. 20 Mule Team Borax is the brand you'll see in the laundry aisle.
• Washing soda (sodium carbonate) is a manufactured alkaline compound — more caustic, with a pH around 11. Arm & Hammer Super Washing Soda is the common box. Despite the brand name, it's emphatically not baking soda: baking soda is sodium bicarbonate (pH ~8.3), much milder, and not a substitute in detergent recipes.

Side by side:

• pH: borax ~9.5 (moderate) vs. washing soda ~11 (strong)
• Cleaning strength: borax is the milder of the two; washing soda is the heavy-duty grease and stain cutter
• Water temperature: borax works best in hot water; washing soda works at any temperature
• Cost: both cheap — roughly $5–7 for a box that lasts many batches
• Safety profile: both are skin irritants; borax is additionally toxic if swallowed — keep away from kids and pets

What Each One Does in Your Laundry

In the classic homemade powder recipe (grated soap + washing soda + borax), the grated bar soap is the actual surfactant — the thing that lifts dirt off fabric. The other two are boosters, and they boost differently:

• Borax: the water conditioner and brightener. It buffers the wash water's pH so the soap works more efficiently, helps soften hard water, loosens some soils, and is genuinely good at brightening dingy whites. It also has mild antimicrobial properties. Its limitation: borax does its best work in hot water, so if you wash cold or warm exclusively — which most households do now — you're getting less of its benefit.
• Washing soda: the heavy lifter. Its strong alkalinity cuts through grease and body oils, softens hard water so the soap doesn't get tied up by minerals, and boosts overall cleaning performance at any temperature. It's also the ingredient that makes the recipe viable in HE washers. In short: washing soda is doing the harder job in the recipe.

Practically speaking, this means the recipe's two boosters aren't equal contributors. If you wash warm or cold — weeknight loads of school uniforms and work clothes — washing soda carries more of the weight. Borax earns its place mostly on the white loads and hot washes: towels, sheets, the quarterly "strip the bedding" load.

Safety: The Part Worth Reading

"Natural" and "harmless" are not the same thing — and with two small kids in the house, this section isn't optional. Here's what each ingredient demands:

• Wear gloves when handling either powder. Washing soda at pH ~11 can irritate bare skin, and borax can irritate skin and eyes too. You only need gloves for the ten minutes of mixing, plus a dust mask if you're sensitive to airborne powder.
• Keep both away from kids and pets. Borax is toxic if swallowed — that's the serious one. Both boxes live on a high shelf, sealed, exactly like any other cleaning product. Never let kids "help" with the mixing step.
• If someone swallows borax, call Poison Control (1-800-222-1222) right away. This is the standard guidance from homesteading and cleaning references, and it's worth knowing before you bring the box home.
• Diluted in a full machine of wash water, the concentration is very low — the safety concern is the concentrated powder on the shelf, not the tablespoon in the drum. Treat them like bleach: respect the concentrated form, don't fear the finished laundry.
• Never mix either with bleach or acids in concentrated form, and rinse skin or eyes thoroughly if you get powder on them.

None of this is a reason not to make your own detergent — it's the same level of caution you'd use with any household cleaner. It's just worth saying plainly, because DIY recipes tend to be casual about safety and these ingredients deserve the gloves-on treatment.

Do You Need Both? The Borax-Free Option

Here is the honest answer the DIY internet rarely gives you: no, you don't need both. Plenty of long-term DIYers run a borax-free version of the recipe and report it works fine for their loads.

• The borax-free variant: 1 finely grated bar of soap + 1 cup washing soda (optionally plus 1/2 cup baking soda for deodorizing). Mix, jar, dose the same 1–2 tablespoons per load. Same ten minutes, same cost per load, one fewer "keep away from children" box on your shelf.
• When you'll miss the borax: dingy whites and hot-water loads. If you notice whites graying over time, add 1/2 cup of borax directly to a white load as a booster — you can buy the box just for that job, and it'll last you a year.
• When you won't miss it: warm/cold everyday loads, which is most of family laundry. Washing soda does the water-softening and grease-cutting that matters most in these.

If you're undecided, start with both and simplify later — or start borax-free and add the box only if your whites tell you to. Either way, you're spending roughly $0.05–0.10 a load, which is why our cost comparison calls this the best budget swap in the laundry room. And if you're comparing DIY to commercial options more broadly, our sheets vs. pods breakdown covers the store-bought side of the equation.

The Verdict

Borax and washing soda are teammates, not rivals: washing soda does the heavy cleaning and works at every temperature; borax conditions the water, brightens whites, and shines in hot washes. If you're buying both for the classic recipe, that's a perfectly good choice. If you're simplifying — or if the safety profile of borax with small kids in the house gives you pause — washing soda plus grated soap alone is a legitimate borax-free detergent that costs just as little. The Tuesday test verdict: whichever version you'll actually mix on a Sunday afternoon is the right one.