The liquid came first – peppermint to be exact. Bar soap meandered in a few decades later. While there are hardliners in both camps, the difference between liquid and bar is mostly a matter of personal preference. However, there are some differences between the two.

Here are the ingredients side by side for the unscented Baby Mild castile soap. I chose our simplest soap, which lacks any essential oils, so that the differences are easier to see.

Comparison of Liquid vs. Bar Castile Soaps

Differences explained:

  • Liquid contains more water.
    • Why: There is just enough water in the liquid soaps to keep them liquid. Any less water and the soap begins to solidify. To test this, leave the cap off your bottle for a day, and you’ll notice the soap’s starting to gel. You can reliquify it with a bit of water. (The thickness, or thinness, of the soap is not due to high water content, but to the consistency of the various oils.)
    • Effect on Performance: None
  • Liquid uses potassium hydroxide to saponify oils; bar uses sodium hydroxide.
    • Why: Hardness – sodium hydroxide produces a harder soap than potassium hydroxide. The purpose of these strong alkalis is to blast apart the oil molecules, separating the glycerin from the fatty acids. The fatty acids then reattach to the sodium or potassium ion, leaving the glycerin and water (hydroxide) free-floating. (Just a sidenote – soap cannot be made any other way. None of these alkalis are left in the soap. Check out the link at the bottom about soapmaking.)
    • Effect on Performance: None
  • Bar contains palm oil, in addition to coconut oil.
    • Why: Palm oil hardens more than coconut oil. Coconut oil, even in its solid state, is mushy, and it melts at 76° F.
    • Effect on Performance: Bar soap is slightly more moisturizing. Palm oil contains stearic acid, which some people find to be less drying than the lauric acid found in coconut oils.
  • Bar contains salt (NaCl – sodium chloride or table salt).
    • Why: Also serves as a hardener.
    • Effect on Performance: Bar soap is slightly more moisturizing. Since our bodies are slightly salty, salt water is gentler on our skin than pure water. Salty soap is, too.

Other Differences in Formulation:

  • How the Hemp and Jojoba oils are added:
    • In the liquid soaps, the hemp and jojoba oils are saponified, i.e. turned into soap, along with the coconut and olive oils. However, in the bar soaps, these two oils are added unaltered after the saponification process. This is called “superfatting” the soaps. A while back my brothers tried superfatting the liquids with the hemp and jojoba oils, but found that the oils separated out and floated to the top.
    • Effect on Performance: Bar soaps produce a creamier lather and are slightly more moisturizing.
  • Amount of Essential oils:
    • This is only relevant to the scented soaps (everything except the unscented Baby Mild). The liquid soaps have a higher percentage of the essential oils than do the bar soaps. Once again, the issue at stake is hardness. The bar soaps would soften with that high a concentration of the essential oils.
    • Effect on Performance: This is entirely a matter of personal preference. Those who like an intense whiff of scent, and those who are looking for the specific benefits of the particular essential oils, should opt for the liquids. Those who like a little scent, but not too much, the bar soap would be better.

Differences in usage:
For all body applications, they are entirely interchangeable – from washing face, hair, or body, or shaving. For around the house purposes, you would need to take the extra step of dissolving the bar soaps in water before using them in a spray bottle solution, but they are equally effective. Also, the bar soap can be grated to achieve a kind of powdered soap for laundry, although the liquid works just as well.

Volume of actual soap:
I don’t know how to de-math this, but people who put together their own recipes for cleaners might want to know this. Bar soaps are 5% water; liquids are 61%. The chemistry is a little different for both, but considering that a bar of soap weighs 5 oz, and thus 4.75 oz of it is soap, you would need 12.18 ounces (a little over 1 ½ c.) of liquid soap to equal the soap content of a 5 oz bar. Doing the math the other way, 1 cup of liquid soap equals approximately (or 3.64 oz.) 2/3 of a bar of Dr. B’s soap.

Bottom Line:
The Dr. Bronner’s Bar and Liquid Pure Castile soaps are interchangeable. However, the bars are slightly more moisturizing. The liquids are slightly more scented.

If you want more info on the process of soapmaking, check out this article:
http://www.drbronner.com/soapmaking_overview.html.

If you have any other questions about what is in the soap and why or where it is sourced and why or anything else, let me know!

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