The thing about a lye-heavy soap "getting milder with enough time" is true. Kevin Dunn did some nice work on this subject; he summarizes his findings in his Scientific Soapmaking book for those with an interest in the nitty-gritty of soap chemistry.
Free sodium hydroxide (NaOH) in the soap will slowly react with carbon dioxide (CO2) from the air to form a milder salt. This salt is sodium carbonate, Na2CO3. It is the same chemical as the white ash that sometimes forms on the top of CP soaps. Sodium carbonate is also the same stuff as the washing soda that is often added to homemade laundry detergent. Although sodium carbonate is basic -- it has a pH above 7 -- it is a much milder chemical than sodium hydroxide. A soap in which free sodium hydroxide has been converted to sodium carbonate will be much gentler to the skin.
Because a bar of soap is a big chunk of stuff, it will take time to convert the excess lye within the soap. If you want to encourage this process, I'd recommend storing the soap so it is exposed to the open air. It's my guess that packaging soap in plastic, for example, might not be the best idea. On the other hand, you don't need to go to the other extreme and run a fan either. Just store the soap on a shelf or in a loosely covered box or whatever and have patience.
Here's the chemistry. First step is for the CO2 to combine with water (from the soap itself or water vapor in the air) to make a weak acid:
CO2 + H2O -> H2CO3 (carbonic acid)
Next, the excess sodium hydroxide (a base) in the soap reacts with the carbonic acid to make sodium carbonate and water:
2NaOH + H2CO3 -> 2H2O + Na2CO3
Yowza! My personal soap calc is coming up with a -43% lye "discount" with AnnaMarie's recipe. The old soap makers would have "boiled and salted" this soap to remove the excess lye, but AnnaMarie's experience clearly shows this soap can be fine as a CP soap if the maker has the patience to let the CO2 do its magic.
edit: I want to add that the old industrial soap makers knew that lye-heavy soap, which was pretty common back then, did become milder with time. But time is money, so they generally didn't cure soap long. They often deliberately sold lye-heavy soap (but NOT this lye heavy!) for laundry and general household use. end edit.
I don't think this recipe would be something I'd unleash on a beginner or someone who doesn't have sufficient patience. I also don't think I'd use this "give it time" approach for a soap that was poorly made -- for example, one that had layers of lye-heavy liquid and oil-heavy soap.
AnnaMarie -- Would you share the link to the SoapQueen post about the recipe? Pretty please?
