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Why Lye In Soap?


fabulousfunfur
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I've been making soap for a while now, and I know how making soap was discovered..............(below)

but do not understand why we add LYE to soap in these day and ages. How do I explain this to soap buyers that lye in soap is caustic but it needs to cure and then the soap is very gentle. How do I explain that cold process soap is very natural when a man made chemical like LYE is added?

Around 1000 BC women noticed the clay from hills was often embedded with sacrificial-animal tallow and ashes from the temple altars, assisted in cleaning their wash.

The discovered the chemical process, now termed as saponification.

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We use it because you have to have lye to make soap. Can't make soap without it, really. Lye is what causes the chemical reaction that changes oils/fats into soap, and without it you'll just have a big bar of lard.

After curing the soap (or cooking it), there is no longer any lye left.

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To make soap you need to create a chemical reaction between fatty acid and an alkali called saponification.

Acid and alkali are the two extremes poles of the pH scale. When creating a chemical reaction, you must have something from either end of the scale in order for your ingredients to react to make the desired product.

The fatty acids in the oils neutralize the alkali in the lye and creates soap. If your recipe and measurements are correct no lye remains.

Lye is a natural occurring substance. According to the American Heritage Dictionary - Lye is obtained by leaching wood ashes. Of course today lye companies do not go out in the woods and collect it out of old dead burnt out tree stumps, it is made in factories. The same like a vit C tablet is not carved out of an orange but made in a factory. Like many different natural occurring products.

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The 'lye' that comes from wood ashes isn't actually the same lye we use today - it is potassium hydroxide. That gives a soft soap after saponification (why we use KOH in liquid soap making). Then they used to add salt, which changed out some of the potassium for sodium, creating a harder bar.

Saponification is a reaction. Most people who don't understand chemistry don't understand reactions, and that what you end up with doesn't have anything to do with what you start out as.

If you have soap, a very strong base was in the reaction somewhere during the life cycle. Course, if you don't want real soap, you can use other surfactants that come from a lab :)

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Most people who don't understand chemistry don't understand reactions, and that what you end up with doesn't have anything to do with what you start out as.
For such people, you could give the analogy of baking a cake. The end result (cake) does not have any resemblance to the raw ingredients (eggs, sugar, etc) that went into it.
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