Even if a product has sodium hydroxide in it, the ph level can be neutral and non-corrosive as long as it has been through a process called,

SAPONIFICATION

http://en.wikipedia.org/wiki/Saponification

http://unclejonssoap.com/howto.html

Basic facts about soap making. (From unclejonssoap.com)

It should be noted that for saponification to occur, oils, fats and the alkali must all be in liquid form. For this reason, water is needed to dilute the alkali, and oils or fats that are solid at room temperature must first be placed on a heat source to melt.

The alkalis used for soap making are sodium hydroxide (chemical formula: NaOH), and potassium hydroxide (chemical formula: KOH). In their pure form, both NaOH and KOH are solid (powder or flakes). When we talk of "alkali", we refer to sodium or potassium hydroxide, in general. When we talk of "caustic soda", we usually refer to the same thing - whereas a "caustic solution" or "lye solution" is the strongly alkaline liquid made by dissolving pure NaOH or KOH in water.

In case you're wondering, there is no way for making soap, and even less natural glycerine soap, without an alkali. For the fatty acids (fats and oils) to turn into soap, caustic soda must be used - no alkali, no chemical reaction, no salt and no soap. However, properly made natural soap contains some extra fatty acids (which are very good for your skin), plenty of natural glycerine (which, too, is good for your skin), and no free alkali - which is quite the opposite to what happens with factory soaps... even the mildest!

Saponification

Saponification is another essential term of soapmaking vocabulary. It means “to turn into soap.” The reaction between the lye solution and the oils is called saponification. Saponification starts as soon as the lye solution and oils come into contact. The liquid, such as water or milk, for example, facilitates the reaction by making sure all the various molecules get together.

The saponification process continues until all the alkali and acid (the lye and the oils) have reacted. In cold-process soapmaking, this can take a few weeks or more. As the soap ages, the reaction slows down considerably, and eventually no unreacted alkali remains. “Young” soap will still have some alkalinity, and this level decreases as the soap ages.

Alkalinity, and acidity as well, is measured on the pH scale. This scale is divided into a range of pH measures from 0 to 14. Substances with high pH factors, such as lye, are “alkalis” or “bases,” while those with low pH factors, like vinegar, are “acids.” Neutrals are found in the middle, around pH 7. Your soap should have a pH between 6 and 10.

A soap is said to be “fully saponified” when there is exactly enough oil and lye to fully react. Since you usually want a little extra oil in your soap, for gentleness and moisturizing benefit, most soaps are formulated with slightly more oil than will completely saponify.

Trace

The term trace refers to the presence of traces of the soap mixture on the surface of the mass when some is taken up on your stirrer and dribbled back in. If the dribble makes no mark, your soap has not traced. When it leaves a little lump on the surface that sinks in quickly, it's beginning to trace.

A trace state is described from “light” to “heavy.” A soap is said to have reached “full” trace when it is at the state desired to do what you need it to do next. When a soap mixture “traces,” it has reached a certain level of saponification and you will add color, scent, and other materials at varying levels of trace. As you gain experience, you'll be able to recognize the signs of trace with no problem at all.

When the oils and lye solution are first mixed, the solution will be transparent, and as you stir, it will become less so. Opacity and a slight graininess lets you know that your soap is tracing. There is also a subtle “soap smell” that comes at the same time. It isn't possible to describe it, but you'll come to recognize and be reassured by it.

If you've made gravy or pancake batter, you've experienced the changing texture that many soapers compare to trace. A light trace may be like a thin pancake batter, a medium trace like a medium-thick gravy. If your soap gets gloppy, you've got a heavily traced batch, and you need to get it into its mold as soon as possible.

Trace issues will cease to be issues at all as you make more and more soap. You must stir your soap to trace before pouring. If your soap hasn't traced, it will likely separate and remain unsaponified in layers of oils and lye solution. There are some recipes that have special trace needs, and they are indicated in the recipe instructions.

Superfatting

This is called “lye discount” or “superfatting.” You may create a gentler soap by calculating a lye discount into your recipe. A lye discount is a reduction from the total amount of lye needed to saponify the oils to a lesser amount. Another way to create a gentler soap is to superfat, by adding extra oils at the end of the stir, before you pour. Overly lye-discounted or super-fatted soap is softer and prone to rapid spoilage. Lye-heavy soap is a worse problem, as it makes harsh, caustic, and unusable soap.

Most lye soap recipes are created with a 3 to 7 percent lye discount, and most of them contain one or more superfatting agents. If you want to add more superfatting agents, keep it to 1 tablespoon per pound of oils, or you'll get soap that is soft and spoils more quickly. You may prefer to add the superfatting agent at the beginning and calculate it into the oils when you make your own formulae.

It is a good idea to clean up as you go. With lye soaps, use kitchen sink to corral the lye-touched objects as you finish with them. Rinse the lye pouring pitcher with water and a splash of vinegar, then fill it partway with water and more vinegar so you can place the other things in a neutralizing bath.

Mise en Place.. huh?

Mise en place is a term borrowed from French cooking. It refers to the practice of measuring out all the ingredients ahead of time and putting away everything except what you'll be using in your recipe. This is a good habit to get into as a soapmaker. It helps you to get organized and stay focused while you work. Make a checklist and go over it before you begin to help you make soaping less stressful. As for the name...? I just call it planning ahead.

Common Soap Making Methods

Although there are other ways to make soap, I am only going to talk about the two "old school" methods here. Not to say that there is anything wrong with the other methods. I just don't have any experience with them and I am a bit of a purist when it comes to certain subjects.

CP & HP Soap Making

What is CP soap?

In short, CP (cold process) method is a way to make soap without applying any extra heat. By definition, it is impossible to make really "cold" soap. This is because soap is the product of a chemical reaction (called "saponification") where fatty acids, combined with an alkali, give a salt (=soap) as the final product. You probably remember from your school days that this type of chemical reaction is exothermic - in other words, it creates it's own heat through the chemical process.

What is HP Soap?

HP is "hot process" soap. It is called hot process because the saponification process is acellerated with heat. The is soap made similar to cold process soap ~ using oil/fat/nut butters, lye and water. The ingredients are brought to trace. The soap is then exposed to heat and "cooked" through the saponification process, usually in a crock pot or double boiler. At this point fragrance and color added and the soap is place into a mold. The hot process somewhat changes the appearance of the finished soap, but allows the soap to be fully saponified and immediately ready for use within a few days.