This is how I make liquid soap, using all the natural oils and no surfactants. This results in a very mild, gently cleansing soap. I suggest you read "Making Natural Liquid Soaps" by Catherine Faillor, for more details and for beginner recipes.
With my process, there's no alcohol to add, no rigged up double boilers, and no bungee cords and plastic to tie to your pot. It literally cooks in the oven!
Edited on 7/22/10 to add:
Not having a recipe in this instructable seems to be a big problem for a lot of people, so I have decided to add one. This is the recipe I used in this instructable:
24oz soft oil of choice (I use Soybean oil)
21oz coconut oil
3oz Cocoa Butter
36oz distilled water (to dissolve the lye)
To neutralize: 3oz Borax + 6oz water heated until borax dissolves, then add to your soap
To dilute your soap: depends on how thick or concentrated you want your soap.
Here is link to some free recipes: http://www.snowdriftfarm.com/form_liquidsoaprecipes.html
This instructable is only meant to serve as a 'picture guide' with basic instruction. It is written under the impression that the reader has some experience with soapmaking, and is looking to explore hot process liquid soapmaking. Please observe all the usual soapmaking precautions!
Check out my blog at http://jesplayin.blogspot.com
Here is a very basic list of what you will need.
Stainless Steel Pot
Stainless Steel Utensils (Very important, Lye will eat any other metal, and heat will melt plastic.
A very accurate Scale that will measure up to the size of your batch
An assortment of bowls, and spatulas
Distilled water (very important, tap water will keep your soap from forming. Not sure what spring water will do, I've never tried it.)
Your lye (Potassium Hydroxide, KOH, Caustic Potash)
Step 1: Weigh Your Ingredients
Make sure you are as accurate as possible. Usually there's a slighly higher lye amount used in liquid soaps than bar soaps, in order to make sure that the fats are completely neutralized. This excess lye will be neutralized later.
I make my liquid soap in an electric oven, set at 250 degrees fahrenheit. Your mileage may vary.
Set your oven to this temp when you first start weighing your ingredients, so your oven will be ready when you are.
It's usually better to weigh your lye and water first to allow some cooling time for the lye, as it takes the lye longer than the oils to cool. Remember, ADD YOUR LYE TO THE WATER, NOT THE WATER TO THE LYE, unless you like explosions in your kitchen.
Melt your oils in the big pot you will mix in, then add the lye water mixture, and commence to mixing!
Step 2: Mix, Mix, Mix
Let your lye solution cool down to about 140 deg F, and your oils to about 160deg F, give or take a few degrees.
This step is easier if you have a hand blender. Liquid soap takes a little longer to 'trace' than bar soaps. On average, it takes me about 15 minutes of on and off mixing to get to trace. Be careful not to wear out your blender. Once it starts getting warm, it's time to take a break.
This is what 'trace' looks like in liquid soap (Photo 2). It looks a little like applesauce, kind of thick and slushy. It's when your stock has thickened enough for you to raise your spoon/blender, and trail a 'trace' on the stock.
Now the fun begins.
Step 3: It's Oven Time...
Once you've achieved trace, then it's time to pop your stock in the oven with a lid.
I usually set my kitchen timer to 15-20 minute intervals to remind me to check the stock, otherwise I will end up with a burnt, congealed mass (This has happened to me before). The timer only works if you can hear it, so make sure you stick around...
From this point on, you're basically just watching, stirring, and waiting.
Step 4: 20 Minutes Later
Your soap looks like really thick white soap...be careful, the lye is still very much active.
You will stir the stock to make sure it's evenly mixed, then pop back into the oven.
Step 5: Another 20 Minutes
The soap is a paste. Stick your spoon in there, and you will find that there is liquid on the bottom. Alas, your paste has separated! No worries, this is normal. Just stir back together with a blender. Continue to cook.
Step 6: After an Hour...
Your paste will look like laffty-taffy. No matter how tempting, do not put in you mouth!
Shortly thereafter (another 20 minutes or so) it gets SOLID! From this point on, it will be pretty hard to stir, which is sort of okay, because you don't have to do too much stirring.
Usually at the point, you have bona fide soap, the lye and fats have fully combined. From this point on, you're working on the clarity of the soap. Do not stop here, however, as you still have to neutralize the remaining lye.
It is okay to leave your paste and go to bed now (if you're working late). You can turn off the oven and pick it back up in the morning with no problem.
Step 7: After 5 Total Hours of Cooking...
You will usually have a lovely amber colored translucent soap paste. Notice how the soap has bent my spoon while trying to stir.
This is the holy grail of liquid soapmaking, and you have found it! You want this color and translucence, because it means that when you dilute your soap stock with distilled water, it will remain clear, I promise you.
Step 8: Time to Dilute
It is now time to take your soap from stock solid, to ready-to-bottle liquid.
Please refer to your recipe/book for dilution ratios, tips and tricks.
Also at this point it is time to add your borax, which will neutralize your excess lye. Again, refer to your book for amounts. The borax also serves as an emulsifier. The nature of the soap (once diluted) is to congeal back together, but the borax serves to loosen that surface tension to keep your soap liquid.
This is also where you will add your glycerin, if you so desire. Glycerin adds an extra layer of emollient and moisture.
Stick your pot back in the oven, and continue to cook, until all the soap has melted into your water and you have a consistent texture.