shave soaps revealed...

Stupid question: why are the Bond Street, Tabak and other shave soaps brands exclusively for shaving? I mean I used bars of Dove and Pre de provence in my life, but I don't think you can shave with those. So, what distinguishes a soap as one to shave with?

Thought I knew the answer, but after heading to a couple of nonshaving stores with soaps, I realized I had no clue, why a shaving soap was just that and a bath soap bar was not the same, or maybe it is?

Austinoire,

I do not have an answer to your question but there are members of DFS who are expert shave soap manufacturers whom I am sure will come up with an explanation.

But if you want an instant completely unscientific answer just try shaving with an ordinary hand soap.
I have and I quickly satisfied my curiosity.

Mickey

Stupid question: why are the Bond Street, Tabak and other shave soaps brands exclusively for shaving? I mean I used bars of Dove and Pre de provence in my life, but I don't think you can shave with those. So, what distinguishes a soap as one to shave with?

Thought I knew the answer, but after heading to a couple of nonshaving stores with soaps, I realized I had no clue, why a shaving soap was just that and a bath soap bar was not the same, or maybe it is?

Shaving soaps are specifically formulated to produce dense, very slippery lathers that do not cleanse especially well. If you look at most bar soaps (Ivory and Dove are rumored to be exceptions, as is Yardley Cocoa Butter), you'll find high levels of either palm kernel oil or coconut oil (or both), in various saponified listings. They're both lathering agents that produce big, loose bubbles and foamy, rather than creamy, lathers. Additionally, most shaving soaps incorporate some level of potassium lye (which is different from the sodium lye that you would use to clean your drains). The potassium salts of fatty acids (ex: potassium stearate) are more soluble in water due to their unique molecular structures, which makes the soaps easier to lather, but can also makes them softer (which can be both a blessing and a curse, since high-stearic soaps tend to be crumbly and brittle otherwise).

In contrast, most good shaving soaps contain high levels of saponified stearic acid, which produces a very dense, creamy lather with microscopic bubbles rather than the large bubbles that you would see from hand soaps. Castor oil is often used to enhance this effect, since the ricinoleic acid that largely comprises it produces a similar lather, but the oil acts also acts as a lathering agent (in contrast, stearic acid without a lathering agent will barely lather at all; same is true for tallow). One of the best (but weirdest) shaving soaps that I've ever seen was a take on the classic MdC formula, but replaced the coconut oil in MdC with castor oil. It was like shaving with frosting when lathered, but was so soft beforehand that it was extremely difficult to work with.

Anyway, the point here is that shaving soaps must produce dense, creamy lathers with few-to-no visible bubbles or the soap will fail to protect the skin properly. This requires a completely different type of soap chemistry than that used in bath soap.

...though I've found Stirling shave soap to make an excellent winter hand soap (doesn't cause drying/cracking to nearly the extent that regular soaps do).

Great explanation Will, thanks! Austinoire, I would suggest you try a shave with a Barrister & Mann product (or any other quality shave soap for that matter) and then try one with bar soap. You will soon know the difference and realize they are miles apart even though they are both called "soap".