cp = cold process. cp is the method by which i make my soap and refers to the fact that (generally) no additional heat is added to the soap mixture to assist the chemical reaction. the heat generated by the soap itself is enough to complete the reaction.
basic chemistry lesson is here. i recommend reading it because imho, if you know what is going on in your soap pot you can better control the outcome. i.e. soap you enjoy versus icky soap.
do not use drano or any other "mixed" drain cleaner. red devil lye is what i use and what i have always heard recommended for soaping. it is straight NaOH and usually found in the drain cleaner aisle. it will be in granule or flake form, usually in white 18 ounce bottles with a red lid. if you shake it you can hear the granules inside. unless you can get your NaOH direct from a chemical company and you know 100% for sure that it is pure NaOH, i'd stick with red devil.
a note of caution: you do need to work with a strong base in order to complete the chemical reaction, so be careful. NaOH can cause severe burns if you are not careful. remember that scene in fight club where brad pitt kisses edward norton's hand and then pours NaOH on it, and he screams and writhes in pain from the burn? i don't know how realistic that is, but just keep it in mind. wear goggles and gloves. NaOH in solution can be even more dangerous because it is dissolved in water and therefore reacts easier with oils than NaOH in crystal or flake form. and it is HOT. raw soap can also be dangerous because the saponification process is not complete so there is still free NaOH floating around in there. at my house, i always let my husband know when i am making soap so he can stay out of my way. that way he doesn't bump me or cause an accident when i am handling it and possibly spill something on myself or himself.
that being said, don't freak out - just be careful. you use sharp objects and play with fire every night when you cook, and you know that as long as you take the proper precautions (you don't leave potholders too close to the burner, you're not careless with the knife when chopping carrots), no one gets hurt. same with soaping. treat NaOH and raw soap with the same respect you treat your knife and burner, stay aware, and you'll be fine.
the baby soap recipe is a good one to get started with; if you can't find pure shea butter, just leave it out and reduce the amount of NaOH to 5.625 ounces. please note that all oil and NaOH measures are in weight, not volume. so you will need your kitchen scale to make soap. also in that recipe, if you can't find calendula oil, don't worry - it's not critical to the recipe. coconut oil can be found at your local natural foods store, same with essential oils. if you don't like lavender or tea tree, use something else. my general rule of thumb is approximately 1 T. eo to 1 lb. soap (by oil + NaOH weight).
coconut oil is solid at room temperature, so you may need to nuke it in the microwave for a minute or two to soften it up enough to get it out of the jar. as far as olive oil goes, better soap is made from lesser grade oil, so don't bother using your expensive extra-virgin. just get the cheapest stuff you can. same with corn oil. it's just soap, people, not gourmet cooking.
you do not need special equipment to make soap. you do need a non-reactive pot, so don't use aluminum or copper if you have them. your regular stainless soup pot is fine, the soap will not soak into it and make all future soup taste funny. it is very helpful to have a stick blender (sometimes called a soup blender or an immersion blender) on hand as it makes stirring a lot easier, but you can stir with an old wooden spoon. kitchen thermometers are very helpful for novice soapers.
you can use anything for a mold as long as you can get the soap out of it in the end. i currently use a silicone-lined mold made especially for soaping, but when i started doing this the best thing i found was to use a shoebox lined with freezer paper. not waxed paper - freezer paper has a plastic coating on one side; use the smooth plastic side facing the soap and crease well. if you have a silicone baking pan, that would be wonderful also because it would be easy to remove. plastic tupperwares work well also but i'd spray them with pam first and you might have to pop them in the freezer if the soap doesn't remove easily.
1. have your ingredients measured and ready before you start. sometimes things can happen quickly when soaping and you don't often have time to pause and measure specific amounts of eo's. so just have everything ready to go before you begin.
2. measure water into a glass pyrex measure; it's best to use cold cold cold water. measure NaOH and carefully pour into the water, stirring constantly. do not pour the water into the NaOH as this could cause a "volcano" reaction. the initial reaction will fizzle a bit and give off nasty acrid fumes, so i find it easiest to do this under the hood vent on the stove (while the stove is off but the fan is on) while holding my head back as far as possible. keep stirring until everything is dissolved (i use a stainless dinner spoon) and then allow it to cool to about 100º-120º, about lukewarm. do not stick your finger in the solution to test it.
3. measure oils into a large non-reactive pot and melt them together. allow to cool to about 100º-110º. oil takes a lot longer to cool than NaOH solution so be judicious about using heat. i usually heat just until the coconut oil has barely begun to melt and then stir so the warmed liquid oils can melt whatever is left solid. oils should also be about lukewarm. the idea is that the oils and the NaOH solution will be approximately similar temperatures when you mix them. if they are drastically different you could have an adverse chemical reaction. you can play with that on your own time, for this tutorial we're going to play it safe.
4. stir the NaOH solution again in case anything has settled; sometimes a "skin" forms on the top or you get little "floaties" in the solution while it is cooling. don't worry about these, they are not a problem. and see how the solution has gone from cloudy white to relatively clear-ish while it cools? that's why i tell my husband when i'm soaping, so he doesn't mistake NaOH solution for something innocuous and hurt himself. and so he makes sure the cat is not underfoot and not trying to drink the solution, thinking it's water. carefully pour the NaOH solution into the oils, stirring with a large non-reactive spoon.
5. keep stirring. and stirring. and stirring. (this is where that stick blender comes in.) see how the oil turns cloudy and you are starting to get more opaque streaks? that's soap starting to form. stirring by hand can take upwards of 45 minutes so i cannot recommend a stick blender enough. i got mine at the drugstore for $17 and i use it for everything, not just soap. stir until your soap mixture is about the consistency of cream soup. this point is called "trace," because you can drizzle raw soap onto the surface from your spoon and your squiggle will "remain" on the surface. other than the cream soup analogy, i don't know how to describe trace but you will know when it happens. if you use a stick blender it will usually be after about 5-10 minutes. if the mixture gets thick and gloppy you've gone past trace and you need to get it into the mold.
6. trace is the point at which you add anything that you might want to add to your soap - essential oils and other fragrances, colorants, and additives like oatmeal, milk, or honey. (you can also use milk as part of your water but be aware that the reaction with the NaOH will make your soap smell like cat pee at first, the smell does go away.) milk and honey will raise the temperature of your soap and discolor tan to brown so don't use them if you want white soap and you probably don't need to insulate. the baby soap recipe will make a nice, creamy-white bar. stir stir stir to be sure everything is blended.
7. pour the raw soap into your prepared mold. don't scrape the pot with a spatula. the idea is that you could inadvertently be scraping raw NaOH solution into your nice batter there. i do scrape the sides lightly with my wooden spoon because i don't like the waste, but i never use a spatula.
8. cover and insulate your mold and put it in a warm spot (or at least, not a cold drafty one). i just pack towels around mine and leave it in a warm spot in the family room. soap is not going to leak out of your shoebox (if you've lined it properly) and if you push it into the corner no one will mess with it, unless you have little kids. be sure to insulate well; this conserves the heat needed for the reaction. if you insulated well and you peek at your soap in 2-3 hours, you will see the center especially looks kind of jelly-like. this is called the gel stage, and if you hold your hand down close to the soap you can feel the heat from the reaction coming up off of it. don't worry if your soap does not gel, it isn't unsafe or anything if it doesn't.
9. allow to sit for at least 24 hours, preferably 48, before unmolding and cutting into bars. this is so it will be firm enough to cut, but you'll notice that your soap is still a bit soft - you can leave fingerprints and indentations on the surface.
10. allow the bars to "cure" for 4-6 weeks to allow the water weight to dry out from them and allow the bars to firm up. you don't have to allow them to cure, but your soap will last a LOT longer in the shower if you do because it won't just dissolve under the spray. don't worry if a white "powder" seems to form on the sides of your bars. it's called soda ash and there doesn't seem to be a reason why it forms. sometimes it does a lot and sometimes it doesn't, and most often it does on the side that was exposed to air while in the mold. it's not harmful, and if you don't like the way it looks you can scrape or wash it off.
11. enjoy your handmade soap! i have found that the first time i use a bar it will be a bit "sticky" on my skin (kind of slidey, slidey, stick); i think that might be mild soda ash formed during the cure. in my experience it goes away after one use. also, i bevel the edges of my bars with a potato peeler. it's personal preference, but i like that there isn't a "sharp" edge when i first use it, and it also helps to hide any little mistakes i make when cutting.
a note on cleanup: i just stick everything in the dishwasher afterwards, because then i KNOW it has been thoroughly cleaned. i'd make sure to rinse out the soap pot well especially, i usually scrape it with the wooden spoon while running water into it while it's in the sink, to get the big raw soap chunks out. (don't worry, they work as a gentle drain cleaner.) i think when the dishwasher leaked it was because i forgot to rinse my soap pot and probably made too many bubbles in the dishwasher, so just get the big'uns off. i usually try to wait until the dishwasher is mostly full so i'm not running an empty washer nor allowing the NaOH-solution-glass to drip on the dishes underneath and then hubby moves a dish and burns his hand. if it is mostly full then i can just put the soap dishes in the washer and run it immediately once the soap is in the mold and insulated.