I had a commenter ask about soapmaking earlier today, and — come to think of it — it’s been a while since I’ve blogged about the process, so people may not know exactly what it is or how I came to be involved.

I learned cold process soapmaking in preparation for my 2005 mission trip to Kenya, so that I could teach it as a cottage industry. Our LEAMIS trip was split that year between two different locations. Carolyn Schussler, who had taught soapmaking in 2004 in Nairobi, would teach a more advanced class in Nairobi in 2005, so someone else was needed to teach the class in Keumbu. Carolyn gave me a quick lesson during our pre-field orientation, and then I went to visit her and her husband in Bay St. Louis, Miss., just two months before Katrina devastated the area, for some followup training.

Soapmaking requires combining a fat with an alkaline substance, usually lye. Most hobbyist soapmakers learn using lard, because it’s inexpensive and makes a good, basic bar of soap. As you get into the hobby, you begin experimenting with different combinations of oils — this one for lather, that one for skin conditioning, another one for a nice hard, long-lasting bar.

The fat or oil is melted down in a stock pot. The lye (which is dangerous and must be handled carefully) is dissolved in ice water, which immediately causes the water to heat up. When the hot lye water has cooled off a bit and the fat is melted and warm, but not too hot, you remove the fat from the heat and carefully stir the lye water into the fat. “Cold process” soap means that this mixing of the fat and lye takes place without any added heat. “Hot process,” which is what our ancestors used, involves cooking the two together.

When I teach soap-making in Kenya, I have to tell my students to stir constantly for the first 30 minutes and then frequently for an hour or more after that. It takes that long, when stirring by hand, for the mixture to form enough soap to bind the oil and water together. If you stop stirring too soon, they will separate, like an oil-and-vinegar dressing. What you are looking for is a condition called “trace,” where the soap mixture is thick enough that you can pull out the spoon, dribble a little bit of the mixture on top of itself, and still see the line, at least for a few seconds.

If you have easy access to electricity, you can achieve trace much more quickly — in five or ten minutes — by using an immersion or “stick” blender. (Emeril Lagasse calls it a “boat motor.”)

Once the soap has traced, you stir in any last-minute additions and pour it into molds. I use those semi-disposable plastic storage containers like GladWare. The store brand of these containers included a size meant for carrot sticks and the like which is just about the right for a bar of soap. You can also buy fancy decorative molds at places like Hobby Lobby.

The soap must cure for at least a month, to make sure that all of the lye has reacted with fat and become soap. And you must do all your measurements by weight and use a very exact formula. Too much lye, and your soap is powdery and can irritate or even damage the skin. Too much fat, and it’s soft and greasy. The perfect mixture is waxy and hard, like a store-bought bar of soap — only better.

Hand-made soap still contains all its skin-conditioning glycerin. Glycerin is a normal byproduct of the soap-making process. (Clear soaps are sometimes called “glycerin soap,” which is a misnomer; all soap is glycerin soap.) But glycerin is used in so many cosmetics, from toothpaste to hand lotion, that industrial soap-makers extract some of the glycerin from their soaps so that they can use it elsewhere (or sell it). Hand-made soaps therefore have more glycerin than store-bought.

As I hinted in my post yesterday, adding colors or fragrances at trace is sometimes risky. The warm, pourable soap is still pretty alkaline and sometimes kills off or transforms whatever you add at that point. You may be better off waiting until the soap has cured and “re-batching” it by grating it into a double boiler and melting it down. But I sometimes have trouble getting a nice, smooth melt out of my own re-batched soap.

If you would like to experiment with shapes, fragrances and colors, but don’t want to fiddle with the lye or the long curing time, you can work with “melt and pour” soap, which is what my sister-in-law and nephew in California did recently. At Hobby Lobby, or on the Internet, you can buy “melt and pour soap base” in white or clear forms. This is an unscented, uncolored soap which has been formulated to melt smoothly and evenly — the Velveeta of soaps. Once you have melted it in a double boiler, you can add any fragrances, colors, abrasives or (for the clear soap) decorations you like, and pour the melted soap into molds of your choosing.