The lye is considered a powerful natural detergent, is an alkaline solution containing sodium hydroxide (commonly called caustic soda) or potassium hydroxide (commonly called caustic potassium). Both sodium hydroxide and potassium hydroxide have strong corrosive properties. Potassium hydroxide is used by the food industry as an additive with an acid regulator function and is identified among the ingredients with the initials E525.

The uses of lye

The uses of the lye are not limited to the production of soap: the lye is used in the food industry, for the production of degreasers and detergents, for the production of drain cleaner. There have been unlawful too: the lye was used to remove the ink from banknotes and documents in order to carry out counterfeiting works. Another illicit use of lye is seen as a synthetic ingredient of amphetamines.

Lye for soap production

In the article “Handmade Organic Soap: protect your skin while having fun and save money” I explained how to produce soap from lye. For the production of lye at home we have used simple ash: the ash contains potassium carbonate or potash, ideal for the leaching process. Sodium hydroxide and potassium hydroxide are used in soap production: sodium hydroxide is usually used to make solid soap while potassium hydroxide is commonly used for the production of liquid soap. Soaps produced from potassium hydroxide are softer and can be dissolved in water more easily. Historically, potassium hydroxide was extracted from fern ashes (e.g. Castile soap and Aleppo soap).

How to make lye: two methods

Cold method

The leaching of the ash using the cold method sees rather long times: it will be necessary to leave the ashes in water for a period of at least 3 weeks in summer and 6 weeks in winter. The first leaching phase can be carried out in a plastic container (in a bucket), taking care to mix at least a couple of times a day. Know that waiting times are directly proportional to the causticity of the product obtained: the longer you leave, the lye will be caustic. The ash will settle all over the bottom and you can take the lye with a ladle and then pour it into plastic bottles.

Hot method

Hot leaching has tighter times. To make the lye with the hot method, you will have to:

Sift the ash to remove lumps and un-unburned parts.

Arrange the ash in a steel pot and add 5 of water to each part of ash (ratio by volume, not by weight!).

Boil over a low heat, stir frequently and stabilize the boiling. Cook for about 2 hours.

At the end of the two hours, let it settle and cool. Filter the lye with a cotton cloth. You will get a fairly clear and easy to store liquid even for long periods.

What remains is called cinder paste, even this can be used as a natural detergent, use it to degrease the oven or to clean the BBQ tools.