Olive oil and coconut oil create very different kinds of liquid Castile soap. Olive oil is the milder direction and can produce a comparatively thick liquid soap. Coconut oil gives much higher cleansing and lather but produces a naturally thinner liquid. The better choice therefore depends on what you want the soap to do.
Olive oil: mildness and body
Olive oil is the classic oil associated with Castile soap. In the workshop, I use it when discussing face wash, body wash, hand wash and baby wash. Its cleansing is milder than coconut oil, but it can still give useful lather. It also has an important practical characteristic: an olive-oil liquid soap can become comparatively thick.
Coconut oil: cleansing and lather
Coconut oil sits at the other end of the comparison. It produces very high cleansing and very high lather. For that reason, I particularly associate coconut-oil Castile soap with dishwashing, laundry, floor cleaning, glass cleaning, kitchen cleaning and other applications where stronger cleansing is useful.
Why the thinner soap can be the stronger cleanser
This comparison also corrects a common misunderstanding. Coconut-oil soap may look almost watery, yet it can produce tremendous lather and strong cleansing. Olive-oil soap can look much thicker while being milder. Thickness and cleaning power are therefore not the same property.
What about skin use?
For skin, I do not start from the idea that the strongest cleanser is automatically the best. Our skin is washed regularly and does not usually need the same degreasing action as greasy utensils, clothes or floors. For babies in particular, I prefer the mildness of olive oil because very high cleansing is unnecessary.
And what about household cleaning?
For heavier household cleaning, the balance shifts. Coconut oil becomes useful because its high cleansing and abundant lather suit jobs where more degreasing is wanted. Even here, however, more foam is not always better. A floor cleaner should not create excessive lather simply for the sake of visible bubbles.
The important distinction is not that one oil is universally better. Olive oil and coconut oil give different personalities to liquid soap. Choose according to the cleansing job, the desired lather and the feel you want from the finished product.
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