Absolutely every one of my wet shavers refuses to use glycerin soaps for shaving.
Point blank, glycerin, while creating bubbles, is not a true soap. Like other surfactants, glycerin often has a drying effect that is not desirable for the hot shave method. If you frequent some of the shaving forums, you may also find a dearth of individuals who rave, recommend, or even use glycerin based shaving soaps.
Many of my wet shavers specifically requested a soap that was high in almond oil. First, I obtained an excel sheet with information on the INS, conditioning, bubbliness, and other properties of the majority of oils used in soapmaking today. I found that there were some omissions, but it served as an excellent starting point. Unfortunately, I cannot seem to find where this spreadsheet is located, but perhaps someone else here knows. By creating a spreadsheet based off of these values, I was able to enter the percentage of whatever oil I wanted to use and get a fairly accurate idea of how the soap would perform as a whole. These values did not prove to be the end-all-be-all of my soap recipe formulation, but it was a wonderful guideline. Ultimately, to get the kind of lather that I was looking for, I exceeded the recommended percent of castor oil.
Wet shavers will tell you, should you ask, that the ideal bubble is tiny, but prolific, so that the lather is more like a foam. Even a low-quality brush should be capable of whipping your product into a froth that is as thick as meringue. Hard peaks are highly desirable, as they are an indicator of the multitude of teeny, tiny bubbles which are so important to shaving. Castor oil is vital to a good shaving soap, as it is the oil which will provide the ability to produce these kinds of bubbles.
Furthermore, you will want to superfat your recipe, as common complaints for people who close shave is razor burn, dryness of skin following a shave, and ingrown hairs. While these are not immediately a problem of yours, creating a product that addresses these issues prior to their occurrence adds value to your product. Adding bentonite clay will impart additional slip to your soap, allowing the blade to slide across skin more easily without 'biting' into the skin. Coupled with a superfat of 5% or greater will help protect and moisturize skin as the shave is occurring. The moisturization itself will counteract the drying that occurs when a person washes natural oils off of their skin. Additionally, the moisturization itself facilitates the hair's ability to regrow without being trapped in dry layers of skin, reducing the instance of ingrown hairs.
It is important to remember that when shaving, a person's skin may be irritated by the shave, a blade that is not sharp enough or has imperfections, or your product. It is possibly most prudent to avoid artificial fragrances and colorants, as they may come into contact with nicks, cuts, or simply sensitive skin.
I hope that this post has been somewhat informative and helps you consider your formula. Best of luck creating soap!
