The Myth of Neutral Soap: Why pH 7 is Not the Goal

There are a few persistent myths in the soapmaking world, but one of the most stubborn is the idea that “neutral soap” is the ultimate goal. You have probably heard it before: “Good soap should be pH 7.” It sounds convincing, especially if you remember from high school science that water is pH 7 and that 7 is “neutral.” Somewhere along the way, the message got twisted into the idea that soap should match that number.

The truth is that this is not only impossible for real soap, but it is also dangerous to chase. True soap, made from fats and lye, will never be neutral. It is inherently alkaline, and that is part of what makes it soap. In this article, we are going to peel back the layers of science to see why pH 7 is not the goal for soapmakers, why you should not feel guilty about your pH 9–11 bars, and how you can make gentle soap without chasing an impossible number.

What is pH Anyway?

Let’s start with the basics. pH is a measure of how acidic or alkaline a solution is. The scale runs from 0 to 14. A solution with a pH of 7 is considered neutral. Below 7 is acidic, and above 7 is alkaline. Each step on the scale is logarithmic, meaning that pH 6 is ten times more acidic than pH 7, and pH 5 is one hundred times more acidic than pH 7. The same is true in the alkaline direction.

In practical terms, lemon juice has a pH around 2, vinegar around 3, coffee around 5, and milk about 6. Human skin typically measures between 4.5 and 5.5. On the alkaline side, baking soda is around pH 9, household ammonia around 11, and bleach close to 13.

Soap, made through the reaction of lye and fat, lands naturally in the range of 9–11. This is where it is stable, safe, and functional.

Why Soap is Always Alkaline

Soapmaking is a chemical reaction called saponification. You combine triglycerides (oils and fats) with sodium hydroxide or potassium hydroxide (lye). The triglycerides split into glycerol and fatty acid salts. Those fatty acid salts are what we call soap.

Here is the key: soap itself is alkaline. The very molecules that form when fat and lye combine carry a negative charge on one end. That is why they clean. The negative charge grabs onto oils and dirt and pulls them into water so they can be rinsed away. But that same structure also makes them basic.

If you somehow managed to make soap that tested at pH 7, it would no longer be soap. It would have been neutralized into something else, most likely a free fatty acid or detergent-like compound that would not function the way you want.

This is why every traditional bar soap, whether made by hot process, cold process, or even commercial triple milling, always tests in the alkaline range.

The Normal pH of Soap

In well-formulated soap, the final pH falls somewhere between 9 and 11. Some bars may test closer to 9, while others may hover around 10-11 or even slightly above. All of these numbers are perfectly safe for washing healthy skin.

Let’s compare. Baking soda is pH 9, and no one panics about dusting it on their counters or even brushing their teeth with it. Mild ammonia is pH 11, and while I would not scrub my arms with it, soap sits much lower in alkalinity. Within this 9–11 window, soap does exactly what it should: it cleans effectively, it rinses away, and it leaves the skin refreshed.

If your bar soap consistently reads higher than 11, that is usually a sign of a lye imbalance. Maybe the recipe was miscalculated or the measurements were off. That soap will feel harsh, and it should not be used on skin. But the normal, healthy range for properly formulated soap is alkaline, and that is not a problem.

Where the Myth Came From

So if soap is naturally alkaline, how did the idea of neutral soap become so popular? The answer lies partly in marketing and partly in dermatology research.

As synthetic cleansers became more common in the 20th century, companies began advertising them as “pH balanced” or “close to the skin’s natural pH.” This was true, since detergents can be formulated at lower pH values, closer to that of the skin’s acid mantle. Clinical studies also suggest that cleansers nearer to skin’s own pH can be helpful for people with sensitive skin, eczema, or compromised barriers. These findings contributed to the idea that all soaps should aim for neutrality.

But here’s the important distinction: for people with normal, healthy skin, traditional soap at pH 9–11 does not cause lasting harm. The skin quickly restores its own slightly acidic balance after washing. The alkaline nature of soap is not inherently dangerous, and millions of people use it daily without issues.

For those with certain skin conditions, however, a milder, lower-pH product may indeed be a better choice. This does not mean handmade soap is unsafe. It simply highlights that different products serve different needs. True soap is always alkaline, and that is perfectly fine for most people. Synthetic cleansers exist for situations where something closer to skin’s natural pH may be beneficial.

The Dangers of Chasing Neutral

Let’s imagine you try to make your soap neutral. What would happen?

The first method people often attempt is adding acid, such as citric acid or vinegar. Acids do indeed lower pH. The problem is that they do not just change the reading on your test strip. They react with the soap itself. Soap plus acid breaks down into free fatty acids. This is why your soap turns cloudy or develops strange textures if you add too much acid. You are literally undoing the saponification reaction.

Another approach is formulating with an extreme lye discount. By reducing the lye, the soap may "test" closer to 8 or 9 initially. The problem is that you are leaving unreacted fats in the bar. Too much excess fat leads to rancidity, DOS spots, and a soft, short-lived bar.

Neither of these methods produces safe, effective soap. They produce unstable products that are prone to spoilage or simply fail to perform.

Even more concerning, if someone did succeed in forcing a soap to pH 7, the resulting bar would not behave as soap. It would not lather, would not clean, and might quickly turn rancid. The very qualities we love in soap are tied to its alkalinity. Neutral soap is a contradiction in terms.

What About Skin’s pH?

A common argument is that because skin is slightly acidic, around pH 4.5–5.5, we should only use cleansers that match it. This idea has some truth in it, particularly for people with very sensitive skin.

It is true that the outermost layer of skin, called the acid mantle, helps protect against microbes. Washing with an alkaline soap does temporarily raise the skin’s surface pH. But here is the important part: healthy skin quickly rebalances. Within about an hour, the acid mantle restores itself. Numerous dermatology studies confirm that brief exposure to soap does not harm skin in the long term.

For those with conditions like eczema or psoriasis, however, or for individuals with very sensitive skin, a cleanser formulated closer to skin’s natural pH may be a wiser choice. That is where synthetic cleansers can play an important role. It is not about soap being “bad.” It is about recognizing that different skin types may need different tools.

How to Make Gentle Soap Without Chasing pH 7

If the goal is not neutral, then what is the goal? For the soapmaker, the goal is gentle, long-lasting, and effective cleansing. Here are some strategies that work, all grounded in science:

1. Balance Your Fatty Acids

Every oil brings its own fatty acids to the party. Coconut oil contributes lauric and myristic acids, which produce quick lather and excellent cleansing, but too much can strip the skin. Olive oil provides oleic acid, which creates a creamier, more conditioning bar. Stearic and palmitic acids bring hardness and stability. By blending oils thoughtfully, you can balance lather, conditioning, and longevity.

2. Superfat Smartly

A modest superfat of around 5 percent provides a cushion of free oils that soften the feel of the soap. Going too high, however, risks rancidity. Going too low can leave a bar that feels drying. Aim for moderation.

3. Cure Properly

Curing does not change the pH much, but it does improve gentleness. As water evaporates and crystalline structures form, the bar hardens, the lather becomes more refined, and the concentrations of your additives, glycerin, and superfat all increase. A four- to six-week cure is not just tradition. It is chemistry.

4. Avoid Harsh Additives

Scrubs, salts, and strong fragrances can irritate the skin regardless of pH. Choose additives carefully and test them thoroughly.

5. Educate Your Customers

Perhaps the most important step is sharing the truth. Explain that real soap is always alkaline, that this is normal, and that gentleness comes from formulation, not from chasing pH 7. Customers appreciate honesty, and knowledge builds trust.

Conclusion

The idea that all soap should be neutral has caused confusion, but the science is clear. True soap is alkaline, always has been, and always will be. A pH of 9–11 is not a flaw. It is simply the nature of soap.

For people with healthy skin, soap at this range is safe and effective. For people with sensitive skin or certain conditions, a lower-pH cleanser may be more appropriate. Both can have a place, and both can be good choices depending on the individual.

So the next time someone asks if your soap is neutral, smile kindly and explain the truth. Soap is alkaline because that is what soap is. Neutral soap is not possible, and that is okay. What matters most is creating a bar that is balanced, well-formulated, and made with care. That is the heart of soapmaking, and it is more valuable than any single number on a scale.

If you would like to learn more about the science of soapmaking, visit me at www.ultimateguidetosoap.com