Washing without detergent: grated soap, used oil and lye

Washing clothes with grated soap: the trick grandmothers already used

Grate half a bar of toilet soap and drop it straight into the washing machine drum. That's it. The laundry comes out "bloody lovely, soft and smelling nice", according to the post that started this discussion in the Sustainable Consumption subforum. The author of the experiment did it because he had run out of detergent and had a bar of hand soap in his rented flat. The idea is nothing new: the same conversation recalls that people were doing it twenty years ago, and that soap flakes made from Marseille soap are sold on the market precisely for this purpose.

What happens when you put toilet soap in the washing machine

The first warning comes quickly: any soap will do, but don't add washing-up liquid or substitutes unless you want a foam party that ends up on the terrace. Some have lived through it: half a glass of dishwashing liquid in a washing machine filled the kitchen with foam all the way to the living room doorway. The anecdote, told amid laughter, sums up the real risk of improvising with products not formulated for the drum.

The second warning is technical. A washing machine detergent contains zeolites to soften the water, soap for grease, enzymes for wine, blood or chocolate stains, bleaches, colour protectors and softeners. Toilet soap only covers part of that. And there is an added problem: traditional soaps cope far worse with hard water than detergents based on synthetic surfactants. In hard water areas, the makeshift solution works worse.

Homemade soap from used cooking oil: from the frying pan to the drum

The conversation drifts towards soap made at home from frying oil. The process is simple: store the oil in a jerrycan, let it settle so the dregs sink to the bottom, filter it with a sieve or kitchen paper, and mix it with lye in a well-ventilated basin, stirring with a long stick. The smell of frying disappears in the reaction with the lye. You can add some fragrance, never alcohol. The result, they say, cleans "like a beast" and works for washing up, the washing machine and even as a gift.

But here comes the most awkward voice: a plumber warns that oil down the drain is a plague second only to toilet paper. Lye does change the chemical properties of the oil, but you still shouldn't go overboard pouring soap down the sink, because it can end up as a blockage. The warning is no small matter: the savings from making soap at home evaporate if you have to call out a technician.

How much do you really save with homemade soap?

Very little, if you only look at your wallet. A dose of liquid detergent costs around 20 cents per wash without hunting for offers. Running the washing machine once a day, annual spending comes to about 73 euros. The full calculation, including the lye, the time and the risk of ruining something, leaves the margin at almost nothing. Those who defend the invention reply that it isn't all about profitability: it's a hobby, like spending hours on a forum, and the result smells better than many commercial products.

The discussion also touches on temperature. Modern detergents are designed to work at 30 or 40 degrees, and at those temperatures bacteria are still alive. Washing cleaning cloths, baby clothes and bed sheets together at low temperature is not a good idea if you want to avoid a stomach infection. Grated soap doesn't solve that problem.

Vinegar, salt and the freezer trick

Among the tips doing the rounds, apple cider vinegar in the softener drawer works as a softener and colour protector. A handful of salt helps stop colours running. And for clothes that are merely worn, not dirty, very little detergent is needed, or even shower gel. Dishwashing liquid applied directly to grease stains before putting the garment in the washing machine gives, according to several accounts, amazing results.

The closing note is a puzzling fact: with these cost differentials, homemade soap should have taken over every household. It hasn't. The washing machine remains the most used and least understood household appliance.