Safety Precautions: Some of the ingredients and procedures described below are very unsafe. Neither myself or kuro5hin are responsible for any damage, either physical, emotional, psychological, or property, that may occur from the following of any instructions given here. This is for entertainment purposes only.
Another note: Soap-making is an art and can easily get much more complicated than the instructions given here. This is intended as a basic outline to get you started; there are many useful books and other resources on the intracicies of fat and oil selection, alternate ingredients and cooking methods, and so forth for those who venture deep into the world of soap-making.
So, let's make soap!
First things first, go to the grocery store (and probably the hardware store, too). There are a few things you're going to need.
Lye, otherwise known as sodium hydroxide. This is the dangerous material in making soap. Very dangerous, in fact. You aren't going to want to get any at all on your hands or skin. I have had good experiences using Red Devil Lye, but this is becoming hard to find. Other brands of lye will work just as well, however. Look for this stuff in the cleaning section of your local department store; if you can't find it there, ask at your local hardware store. For your own safety, the MSDS for lye is essential reading.
Oil. Any sort of oil will do. Look in the cooking oils section of your local grocer. Here are the effects of some common oils in terms of the soap they produce:
Olive oil makes very fine, small, silky bubbles that feel nice on the skin, but the soap doesn't work as a hardcore cleanser.
Coconut oil makes huge, fluffy bubbles.
Popcorn oil makes the soap very yellow, but results in large fluffy bubbles, mostly because popcorn oil is by and large the same as coconut oil.
Canola oil makes almost no bubbles at all, but makes a great deal of lather.
Vegetable oil makes a very average soap; medium sized soapy-feeling bubbles.
Litmus paper. This may be the trickiest thing to find; try asking at your local hardware store if you can't easily come across any. If this doesn't work, go to your local swimming pool supply shop, as they carry a wide variety of pH paper. Ideally, you want paper that includes a pH value of 10 in its detection range. pH paper is somewhat expensive, though; one trick is to cut the paper vertically into three or four very thin strips, thus tripling or quadrupling the number of samples you can take with the paper. pH is very important when making soap so that you don't accidentally make a soap that will damage your skin.
An ice cube tray. You will eventually pour your soap into some sort of container to allow it to harden; an old ice cube tray works just fine for this purpose.
A blender or a hand-held mixer. Mixing is crucial. I prefer using a hand-held mixer with plastic blades; the metal can often react with the lye, resulting in not only bad soap but corroded equipment.
A few plastic bowls. These will be for stirring and mixing purposes.
Ice and water.
When you have all of this collected, you're ready to go!
The directions below will make a minute amount of soap, enough to fill perhaps four squares in an ice cube tray. You can multiply the amounts by any integer to make more soap.
First, measure about 1/8 cup of cold water, then add a small ice cube to the water bringing your total amount of liquid to about 1/4 cup. The goal is just to have some very cold water; the measurement doesn't have to be exact. Now, take your lye and go outside. It is a bad move to mix the lye and water in the house, as lye can take the surface off of Formica and damage anything metal that comes near it.
Measure out 1/8 cup lye, and then VERY slowly add the lye to the water, stirring the water slowly. The water will heat up rapidly as you do this, so be careful and do it very slowly. Eventually, the water will clear up; let it sit and return to room temperature. Meanwhile, mesuare out a cup of oil that you plan to use.
Once you have a cup of oil and 3/8 cup of lye water, put the oil in a bowl and then slowly pour in the lye water, stirring this slowly until you've poured in all the lye water. At this point, blend it on low, then slowly increase the speed of the blending.
After about ten minutes of blending, you should stop and scoop out a bit of the liquid soap, and then let it drop back onto the soap. When you drop the soap back on top, check to see whether or not you can observe a visible outline around the drop. If there is an outline, the soap is ready to put into your drying tray (i.e., the ice cube tray); if not, mix the soap for another few minutes and try again. This "outline" phenomenon is called tracing.
Once your soap mix has a trace, just pour it into the tray, put it somewhere dry, and let it sit for a few weeks, with one little exception: after 72 hours, stick a piece of pH paper into one of the soap pieces (it should be of a pudding consistency at this point) and check the pH. If it is at 10 or below, your soap is just fine; if it is above 10, keep checking it daily until it gets to 10 or below. The recipe here should wind up with a pH around 9.
After two to three weeks, you should have small ice-cubed shaped pieces of soap. When the soap is appropriately hard for you (this is up to you), just pop out the soap as if they were ice cubes and seal them in a reclosable bag for storage. The soap may get a thin, white powdery layer on it after a while; this isn't anything to be worried about as it is just soda ash resulting from the carbon dioxide in the air mixing with the soap. This occurs in commercial soaps and is cut away during the shaping and imprinting of the soap.
Wash, and enjoy your homemade soap!
Advanced Techniques If you get the basic recipe to work and enjoy it, there are a lot of things that you can try for your own use:
Melt a crayon and add it to the mixture at the trace stage. This will provide color to the soap. Since crayons are primarily stearic acid, which is a type of fat, the crayon will become part of the soap itself and color it throughout. Don't worry; it doesn't affect the cleaning power of the soap at all. Be sure to mix the crayon so that the color is consistent throughout.
Add a dash of perfume, herbs, or other smelling substances at the trace stage. Mixing in a touch of perfume, natural herbs or flower petals, or other such items at the trace stage adds a hint of color, smell, and texture to the soap.
Cook a fat to use instead of oil. This is very tricky, but results in some wonderful soaps. Be careful that the fat you're using is pure fat, however; if you mix in pieces of non-fat into the mix, it will cause problems with the soap. I strongly recommend trying lard. A tub of lard from the grocery store makes a wonderful soap when mixed with lye; my favorite recipe for soap is mostly lard with a few dashes of other types of oils. It should be noted that lard is harder to make soap with than just oils; thus, try making soap from just oil first.
Additional Soap Resources You may also want to visit some web resources on soap making to get advice from others who have adopted soap-making as an enterprise:
The Soap Making Home Page is probably the best all-around resource for soap making on the web.
Formulas and Recipes for Homemade Soaps contains several interesting recipes for soaps, including a liquid hand soap that I've had some success with.
Also, the following books are recommended reading for potential soap makers (bn links):
Melt and Pour Soapmaking by Marie Browning is a very fun book for beginning soap makers with a lot of good recipes.
The Natural Soap Book by Susan Miller Cavitch discusses soap-making from an all-natural perspective; it has a ton of good ideas for natural ingredients to add to your soaps.
Milk-Based Soaps by Casey Makela and Deborah Balmuth investigates the use of milk in soaps as a supplement to the fats. This is a more advanced book on soap-making, but it's the area I'm currently experimenting with.