A washing-soda laundry detergent is useful for towels and bed linen when you regularly face typical problems: towels smell „musty“ despite washing, light bed linen appears grey, or in hard water detergent residues remain in the fabric. Washing soda (sodium carbonate) is an alkaline water softener and degreaser. It supports the actual surfactant (here: grated bar soap) and improves cleaning performance especially at higher temperatures and with calcareous tap water.
This guide is deliberately structured like a workshop and recipe manual: purpose, ingredients, quantities, tools, preparation, dosing according to water hardness and soiling, machine application, as well as shelf life, labeling and disposal. You will also receive a water hardness table (°dH/mmol/l) and a dosing schedule so you do not have to work „by feel“.
Important: washing soda is not the same as baking soda (sodium bicarbonate). Baking soda is significantly milder and less effective for this task. Washing soda is more alkaline and can irritate skin and eyes — treat it like a household chemical product.
What this washing-soda detergent is suitable for (and what it is not)
The recipe is designed for boil- and color-fast textiles, such as cotton, linen and blends as commonly used for towels and bed linen. It targets odor reduction, improved degreasing (body fats, skin care products), and reduced greying through improved water softening.
Suitable
- Towels, washcloths, bath mats (where washable, usually 40–60 °C)
- Bed linen made of cotton/linen (40–60 °C, whites also 60–90 °C depending on care label)
- Underwear and socks made of cotton (60 °C is often sensible for hygiene if the textile tolerates it)
Not suitable or only with adaptation
- Wool and silk: alkaline solutions damage animal fibers. Use a specialized wool detergent for these.
- Delicate colors/prints: soda can leach dyes faster, especially when combined with oxygen bleach.
- Membrane textiles (e.g. performance wear): soap residues can clog pores; it is better here to use a suitable liquid detergent without soap.
- Very low wash temperatures (20–30 °C): soap formulations dissolve less well and can leave residues. For towels/bed linen, 40–60 °C are usually advisable in practice.
Basic principle: washing soda, soap, water hardness and temperature
To make the application predictable, it helps to understand the three control variables:
- Water hardness (lime content): the harder the water, the more calcium and magnesium ions are present. These can cause soap to precipitate („lime soap“) and reduce cleaning performance. Washing soda binds hardness ions and thereby reduces the load on the soap.
- Temperature: towels and bed linen generally benefit from 40–60 °C. Soap components perform more stably at higher temperatures. For whites and hygiene, 60 °C, occasionally 90 °C, can be appropriate (observe the care label).
- Load/soiling: body fats, creams, hair products and sweat are particularly present in terry and bed linen. Here an alkaline environment (soda) and sufficient mechanical action (do not overload) help.
Ingredients list (with function) for 1 kg washing-soda laundry detergent
The quantities are chosen so that you obtain a powdered detergent that is easy to dose. Optionally you can add oxygen bleach; this is often the decisive component for whites and against odors.
Required ingredients
- 600 g washing soda (sodium carbonate): water softener, grease solvent, supports cleaning.
- 300 g bar soap, finely grated: surfactant/washing-active substance; dissolves dirt and fats. Preferably use an unscented, plain bar soap without conditioning oils.
- 100 g sodium citrate (optional, but recommended for hard water): additional softener (citrate binds hardness builders). Alternatively it can be omitted; then the dosing of soda becomes more important.
Optional additions (depending on laundry)
- 100–200 g oxygen bleach (sodium percarbonate): effective from about 40 °C against graying and odors, supports hygiene. Very useful for whites.
- 10–20 g extra soda crystals (only for very hard water or heavily greasy laundry): as a separate dosing reserve, not necessarily incorporated into the main mixture.
Note on fragrance: For towels and bed linen, “neutral” is often better than heavily perfumed, because fragrance compounds can lodge in terry and mask odors instead of removing them. If you want fragrance, do not add it to the powder (shelf life/clumping); instead use an occasional fabric spray or place dried herbs in the wardrobe. Do not put essential oils in the detergent container: they can attack plastics and are problematic in wastewater.
Tools and materials
- Digital kitchen scale (1 g increments are sufficient)
- Large bowl or bucket (min. 5 l)
- Grater or food processor for soap rasping
- Spoon/spatula for mixing
- Fine sieve (optional, to avoid clumps)
- Funnel (for clean transfer)
- 1–2 tightly closing containers (glass or HDPE plastic), total volume at least 1.5 l
- Label and waterproof pen
- Protective equipment: gloves and, for dusty work, optionally a mask (soda dust is irritating)
Safety and material notes (please read)
Washing soda is alkaline. That means: it can irritate eyes and skin. Bar soap dust can also be irritating. Work steadily, keep things dry and avoid creating a “dust cloud”.
- Store dry, out of reach of children.
- Do not store in food containers without clear labeling.
- Do not mix with acids (vinegar, citric acid) in the same container: this neutralizes the effect and can foam.
- Aluminum can be attacked by alkaline solutions. In washing machines this is usually uncritical, but avoid soda solutions in aluminum trays.
Recipe: Prepare washing-soda detergent as a powder (step by step)
Allow about 20–30 minutes for 1 kg of mixture, depending on how quickly you grate the soap.
Step 1: Prepare the workspace
- Wipe the work surface dry.
- Prepare containers, have the label ready (see the „Labeling“ section).
- Put on gloves.
Step 2: Finely grate bar soap
- Grate 300 g of bar soap finely. The finer it is, the better it dissolves during the wash.
- If the soap is very soft: chill briefly, then grate.
Step 3: Weigh dry ingredients
- 600 g washing soda
- 100 g sodium citrate (if used)
- Optional 100–200 g oxygen bleach (weigh separately, then add)
Step 4: Mixing — minimize clumps
- Add the soda (and citrate) to the bowl first.
- Work the soap shavings in in 3–4 portions, mixing thoroughly after each addition.
- Optionally fold in the oxygen bleach last to reduce dust.
- If necessary, pass once through a coarse sieve to break up soap clumps.
Step 5: Filling
- Fill containers using a funnel.
- Close lids tightly to prevent atmospheric moisture ingress (soda is hygroscopic and can form lumps).
Water hardness table: classify and determine appropriate dosing
Water hardness determines how much water softener you need. In Germany it is often given in °dH (degrees German hardness). Some suppliers state mmol/l. Both are common; for practical purposes a rough classification is sufficient.
| Hardness range | °dH | mmol/l (approx.) | Practical note |
|---|---|---|---|
| soft | < 8,4 | < 1,5 | Good washing performance, little softener required |
| medium | 8,4–14 | 1,5–2,5 | Standard dosing; citrate may be useful |
| hard | 14–21 | 2,5–3,8 | More softener required, otherwise soap scum/deposits |
| very hard | > 21 | > 3,8 | Increase dosing; observe machine maintenance |
How to find your water hardness: On your water supplier’s website, in the annual billing statement, or with a test strip. For dosing planning it is sufficient to know the range (soft/medium/hard).
Dosage plan: washing-soda detergent by water hardness and level of soiling
The following quantities refer to a 4–5 kg wash load of towels or bed linen in a standard domestic washing machine. For 7–9 kg machines the values serve as a basis for a half drum; for a full load adjust accordingly.
Basic dosing (powder)
| Water hardness | light soil | normal soil | heavy soil / odor |
|---|---|---|---|
| soft | 30 g | 40 g | 55 g |
| medium | 40 g | 50 g | 65 g |
| hard | 50 g | 65 g | 80 g |
| very hard | 60 g | 75 g | 90 g |
Oxygen bleach (optional, in addition to powder)
- For white towels/bed linen at 40–60 °C: 10–20 g per wash.
- For odor or the “hotel towel” effect (heavily greasy terry goods): 20 g at 60 °C.
- At 90 °C oxygen bleach is often unnecessary; if used, dose lower.
Dosage shortcut: If you want a single number: start at medium water hardness with 50 g per load of towels/bed linen (normal soil) and adjust in 10 g increments.
Use in the washing machine (detergent drawer, drum, programs)
Where to add?
- Detergent drawer (main wash, compartment II): Standard. Advantage: dosing as usual.
- Directly into the drum (dose ball/pouch): useful if you want to avoid soap residues at low temperatures. For towels/bed linen (40–60 °C) both methods are acceptable.
Programs and temperatures
- Towels: usually 60 °C recommended (follow care label). For more delicate terry goods 40 °C, then consider using oxygen bleach.
- Bed linen: 40–60 °C, white cotton occasionally 60 °C or 90 °C as needed.
- Rinse cycles: If you are prone to residues or have very hard water, „Water plus/Extra rinse“ can be useful.
Loading: more important than many additives
Overfilled drums are a common cause of gray laundry and odors. Rule of thumb: leave about a hand’s breadth of space at the top of the drum so the mechanics can work and sufficient water can circulate.
Pretreatment and special cases (odor, graying, grease, blood)
Removing odors from towels
- Wash at 60 °C, if permitted.
- Dose according to the table towards „heavy soil“.
- Add 20 g oxygen bleach (for white/light textiles).
- Avoid fabric softener: it forms a film on fibers and can promote odors.
Graying of bed linen
- Check hardness and adjust dosing (common error: hard water and insufficient water softening).
- Wash white laundry occasionally at 60 °C with 10–20 g oxygen bleach.
- Keep the machine clean (see section ‚Machine maintenance‘), because biofilm in the machine can promote odors and gray films.
Greasy residues (body lotion, ointments, massage oils)
- Pre-treat the stain with a little gall soap or bar soap, rub in, and let sit briefly.
- Do not choose too cold a wash; 60 °C works noticeably better here than 40 °C.
Blood stains
Rinse blood first with cold water (warm sets proteins). Then wash normally. Oxygen bleach can help on light textiles. Washing soda alone is not the best first measure, but it supports the main wash cycle.
Machine care: avoid residues, preserve service life
Homemade powders containing soap work well if the machine is maintained regularly. Problems usually do not occur “suddenly” but develop gradually through a combination of low temperatures, too little water (eco programmes) and soap/limescale residues.
- Monthly (or every 20–30 wash cycles): a 60–90 °C empty wash cycle. Optional with a suitable machine cleaner.
- Detergent drawer rinse out regularly and let dry.
- Door seal and lint filter check (fibers retain odors).
- With hard water: limescale can promote visible deposits. Correct water softener dosing reduces the risk.
Shelf life, storage and typical quality issues
Shelf life
Stored dry and sealed, the powder is practically stable for several months. The decisive factors are not „spoilage“ as with food, but moisture uptake (clumping) and, for oxygen bleach, the loss of effectiveness due to moisture.
Storage
- Cool, dry, dark.
- Close the lid immediately.
- Keep the measuring scoop dry (do not put a wet scoop into the container).
If the powder clumps
- Smaller clumps: shake or crush with a spoon.
- Strong clumping: press through a sieve and transfer to a drier container.
- If oxygen bleach is included and the powder got moist: effectiveness may decrease; in future store oxygen bleach separately and only add it when dosing.
Labeling (label) – mandatory information for household use
Even if it is a DIY product: clear labeling prevents confusion and helps everyone in the household.
- Product name: ‚Washing soda detergent (powder)‘
- Contents: e.g. ‚1 kg‘
- Preparation date
- Short dosage note: ’40–80 g per 4–5 kg, depending on water hardness‘
- Safety: ‚Alkaline – irritates eyes/skin. Keep out of reach of children. Do not inhale dust.‘
- Ingredients: ‚washing soda (sodium carbonate), bar soap, optionally sodium citrate, optionally Natriumpercarbonat‘
Disposal and environmental aspects
Leftover powder
- Small residual amounts can usually be used up in the laundry.
- If disposing: place in a closed bag in the residual waste to avoid dust.
Empty containers
- Glass containers: rinse out, glass recycling.
- Plastic containers: rinse out, Yellow Bin/sack (depending on regional system).
Washing soda and wastewater
Washing soda raises the pH in the wash liquor, but is attenuated in wastewater by dilution and neutralisation processes. Correct dosing is important: overdosing rarely gives better results, but increases the load and can unnecessarily stress textiles.
Practical checklist: how to start without trial-and-error
- Determine water hardness (soft/medium/hard is sufficient).
- Start with the dosage for ’normal soiling‘.
- Do not overload towels/bed linen; prefer 40–60 °C.
- For odors: 60 °C, higher dosing, optional oxygen bleach.
- For residues: an extra rinse cycle or slightly reduce dosing; maintain the machine.
Conclusion
A washing-soda-based detergent is a robust solution for towels and bed linen when you take water hardness and temperature into account. The recipe of washing soda and finely grated curd soap provides a clear, easily dosed base; adding sodium citrate stabilizes the softening effect in hard water. The dosing plan helps you wash reproducibly instead of experimenting. If you also use oxygen bleach precisely on whites and for odors and maintain the machine regularly, you avoid the typical side effects (residues, gray film) and preserve long-term freshness and a good handle of the textiles.
Washing soda dosing and a water hardness table are also important for this topic. The article explains these aspects clearly and shows what matters in everyday use.