Somewhere in most supermarkets there is a bag of soda crystals that looks like it has been on the shelf since 1974. It costs about two euro, your grandmother swore by it, and half the DIY laundry detergent recipes on the internet list it as the main ingredient. So it is fair to ask: what is laundry soda, and can something that cheap actually wash your clothes?
Short answer: no, not on its own. Laundry soda is a water softener and a degreaser. It is not a detergent, and the difference matters more than the name suggests.
One chemical, four names
Laundry soda, washing soda, soda crystals and sodium carbonate are all the same thing. It is a simple alkaline salt, related to the baking soda in your kitchen (sodium bicarbonate) but noticeably stronger. It is not caustic soda, which is a different chemical entirely and has no business anywhere near your laundry.
Because the names get used loosely, people often assume "laundry soda" is just an old-fashioned word for detergent. It is not, and that assumption is where most of the disappointment with it comes from.
What washing soda actually does in a wash
Washing soda does two useful jobs. First, it softens water: it binds up the dissolved calcium and magnesium that make water hard, which stops those minerals interfering with the wash. Second, it raises the pH of the water, which helps loosen grease and body oils from fabric.
Here is what it does not do. It contains no surfactants, the molecules with a water-loving end and an oil-loving end that surround dirt, lift it off the fibre and keep it suspended in the water until the machine drains. Surfactants are the part of a wash that actually cleans. Washing soda has none.
A useful way to think about it: washing soda prepares the water. Detergent cleans the clothes. One sets the stage, the other does the work. If you have ever wondered why a "natural" wash with just soda left your clothes smelling washed but looking dull, that is why.
Why the DIY detergent recipes disappoint
Most homemade laundry detergent recipes are some ratio of grated soap, washing soda and borax. The washing soda is doing honest work in there. The soap is the problem. Soap reacts with the minerals in hard water to form soap scum, the same grey film you scrub off shower doors, and in a washing machine that film settles into your fabric. The usual result after a few months is dingy whites, stiff towels and a machine that smells.
Ireland and much of the UK sit on hard water, which is exactly where those recipes fail fastest. If you have tried one and watched your whites go grey, the washing soda was not the culprit, but it could not save the recipe either. We wrote a longer piece on what laundry detergent actually is and why it is not soap, if you want the full chemistry.
Where washing soda genuinely earns its place
None of this makes washing soda useless. It is cheap, it is effective at what it actually does, and there are three jobs where it is the right tool.
Machine maintenance: a cup of soda crystals in an empty hot wash once a month dissolves the greasy film that builds up inside the drum and the outlet pipe. Pre-soaking: genuinely greasy items, like overalls or kitchen cloths, benefit from an hour in a bucket of warm water with a handful of crystals before a normal wash. And boosting: in a very hard water area, adding washing soda alongside your normal detergent frees the detergent to clean instead of fighting the minerals.
What you do not need to do is use it routinely with a decent modern detergent at the right dose. Detergents already account for ordinary water conditions.
Do you need washing soda with detergent sheets?
Mostly, no. Our sheets are 58% sodium dodecyl sulfate and 17% fatty alcohol polyglycol ether, which is to say they are mostly surfactant, the working part of a detergent, with 15% polyvinyl alcohol as the carrier that dissolves in the wash (we have written about PVA separately), 9% water and 1% fragrance. There are no enzymes and no built-in water softener. To be straight about the ingredient list: sodium dodecyl sulfate is also known as SLS, and at concentration it is a recognised skin irritant. In use it is heavily diluted across a full drum of water, but if you prefer to avoid fragrance entirely you should know our sheets carry 1% and we do not currently make a fragrance-free version.
The honest concession is that in a very hard water area, a traditional powder has one advantage: powders include builders, essentially washing soda already mixed in. The workaround is simple, because washing soda is sold on its own for two euro: add a small scoop of soda crystals to the drum alongside the sheet on heavily soiled loads. You get the softening of a powder without hauling a plastic tub of it home.
Two other doubts worth answering directly. If you suspect a thin dry sheet cannot clean like the format you use now, remember the sheet is concentrated surfactant, and for set-in stains, wet a corner of the sheet and rub it into the mark before washing. No detergent format shifts a set-in stain unaided, whatever the advert implies. And if you tried sheets before and found residue on your clothes, that is a loading error, not a formula problem: the sheet goes into the empty drum first, never the detergent drawer and never on top of a stuffed load. An overloaded machine stops any detergent dissolving properly, powder, pod or sheet.
One more practical note: washing soda itself is alkaline enough to irritate skin on contact, so wear gloves when you handle the crystals, and keep them away from wool, silk and anything aluminium.
The short version
Laundry soda is sodium carbonate: a water softener and degreaser, useful for machine cleaning, soaking and hard water boosting, and no substitute for detergent. Pair it with a real detergent when conditions call for it, and skip it the rest of the time.
If you want to try sheets as that detergent, ours come with a 30-day money-back guarantee, and subscriptions can be cancelled any time by email or live chat, with no fees and no notice period. The 60-pack of eco-friendly laundry detergent sheets is one sheet per full load, and how much detergent to use is a question with a shorter answer than you would think.
FAQ
Is laundry soda the same as baking soda?
No. Laundry soda is sodium carbonate, baking soda is sodium bicarbonate. They are related, but washing soda is considerably more alkaline and stronger. You can wash with baking soda in a pinch; it just does less.
Can I wash clothes with just washing soda?
You can run the machine with it, and lightly worn clothes will come out smelling neutral. But with no surfactants, oil and dirt are not lifted from the fibre, so anything genuinely dirty comes out dull. Use it alongside a detergent, not instead of one.
Is washing soda a detergent?
No. It is a builder, the industry term for a water softener and pH booster. Detergents contain surfactants; washing soda contains none.
Does washing soda damage clothes?
On cottons, linens and synthetics, no, used at normal doses. Keep it away from wool and silk, which dislike high pH, and from aluminium fixtures, which it corrodes.
What is laundry soda made of?
Sodium carbonate, usually sold as crystals with water bound into them. Nothing else, which is why it is so cheap.