Soaps have been around for thousands of years. Lye, in its present form, was not around throughout most of soap’s history. The caustic alkalies (bases) used for soapmaking were potash leached from wood ashes, and various carbonates produced from the ashes of seaweeds and land plants. The soaps were harsh and soft, and often rather unpleasant. Not until the 1700s, when Nicholas Le Blanc discovered a way to make caustic soda (sodium hydroxide) economically, did soapmaking attain new quality levels.
EARLY ROMAN SOAPS
During the first century A.D., the Romans used urine to make a soaplike substance. It contained ammonium carbonate which reacted with the oils and fat in wool for a partial saponification. People called fullones walked the city streets collecting urine to sell to the soapmakers.
Lye means one thing to one person, and something else to another. Technically, lye has a narrower meaning than alkali or base, and a broader meaning than caustic soda or caustic potash. We, as soapmakers, can speak to one another using these words interchangeably, with full understanding of the intent. But to understand the soapmaking process, we must isolate the individual components and learn how each one contributes to the final product.
Lye has two meanings. It is the solid form of a caustic alkali. It is also the water solution in which a caustic alkali has been dissolved. I most often call sodium hydroxide “sodium hydroxide,” and the sodium hydroxide/water solution, “lye.”
A soap is the neutral product created when the acids of fats and oils react with organic or inorganic bases. Cold-process soapmakers use a variety of fats and oils as the acid, and sodium hydroxide, a caustic alkali, as the base. But many other bases can be used to make soap. The base of choice would depend upon the particular soap. A liquid soap, for example, calls for potassium hydroxide (caustic potash). There are many caustic alkalis, but it is sodium hydroxide which is most helpful to the cold-process soapmaker.
Sodium hydroxide (NaOH), also named caustic soda, comes in three forms: solid, flake, and liquid solution. Solid caustic soda is impractical for the cottage-industry soapmaker. NaOH predissolved in water is called solution, but, unless the chemical company is local, the cost of shipping the water solution is prohibitive. Flake (or bead) lye is easy to store, easy to find, and easy to use.
Though less expensive in 50-pound bags, I choose to buy sodium hydroxide in 13.5-ounce containers at the supermarket. The Memphis humidity is mighty impressive and finds its way even into well air-conditioned rooms. In the presence of moisture in the air, the sodium hydroxide flakes absorb the water and clump into solid chunks. I don’t want to go digging for my measurement of NaOH from a solid mass, nor do I want an inferior solution. I also have health and safety concerns about storing 50-pound bags of a potentially active chemical in my home. So this is one material I prefer to buy in small quantity. Look for Red Devil plastic canisters at the supermarket, normally shelved next to the Drano. Be careful not to use these interchangeably. Also, squeeze the can of lye to be sure that the product has not been exposed to moisture or air. A crunchy can should be left behind. For bulk purchases, contact chemical companies. Ask for well-sealed plastic buckets with a polyethylene liner.
Sodium hydroxide is highly reactive in its dry form or within solution. One bead of lye can burn right through layers of skin in the presence of just a hint of sweat. A splash of solution can burn, blind, or at least eat through a butcher block table.
This compound is worthy of our greatest respect and even greater caution. Sodium hydroxide is corrosive to all tissues. Accidentally swallowed, it causes serious internal injury, and it can be fatal. Even the weaker solutions can do extensive damage.
Ingesting lye can be fatal if we do not act immediately. Past literature instructed people to neutralize any ingested sodium hydroxide with acids, like lemon or lime juice, or vinegar, and then to drink a demulcent, like egg whites or olive oil, which often induces vomiting. Poison control centers now urge people not to use this procedure and not to induce vomiting.
You should check with your local poison control center for the most up-to-date procedures. Be prepared to act should someone ingest sodium hydroxide. As of this writing, the recommended action is to give water only — four ounces for children and eight ounces for adults — and to head to the hospital emergency room. In case of eye exposure, irrigate the eyes with large quantities of running water and seek medical attention. Flood skin burns with large quantities of running water until the soapy, slippery feel disappears, then treat as you would treat any other burn.
CAUTION
Never dispose of sodium hydroxide, lye, or raw alkaline soap without first researching local landfill regulations. These materials are toxic and hazardous.
The disposal of toxic chemicals is a critical issue for many businesses. The soapmaker must be aware of safe disposal, but we have the advantage of creating usable waste. Soap scraps can be recycled, and yesterday’s lye can be used at another time, if it is kept in a safely sealed container. Measurement errors can be corrected by adding more sodium hydroxide or water, as needed.
As your lye cools down for a few hours or overnight, be mindful of exactly where you set down the bowl. Remember to consider children, cats, dogs, and the level of activity in the room. Carefully think through location, as well as all other steps. It’s better to cover all bases, even those remote contingencies.
See chapter 9 for more thorough step-by-step instructions on preparing and using the lye.
More than any other one component of your formula, sodium hydroxide must be handled precisely for a trouble-free batch of soap. An ounce or two less or more of water or of a particular oil will not dramatically affect the final soap. But you will notice that difference with respect to the sodium hydroxide. Measure the sodium hydroxide carefully, using a good scale.
Choose a glass or ceramic container for the water. Look for a pitcher with a lip to avoid splashes. Caustic alkalis attack zinc, tin, aluminum, and brass, and the sturdiest of plastics weaken from the heat of the reaction. Some books give the go-ahead to cast iron and steel, but I don’t advise using either. At higher temperatures, lye eventually eats away at cast iron, sometimes polluting your solution. Stainless steel seems to hold up better, but, with its high cost, I’d rather earmark those pans for cooking. Finding glass or inexpensive, heavy pottery is fairly simple. A rounded bowl is easier to use than a taller jar.
The mixing of sodium hydroxide and water generates considerable heat; to stir the lye solution, I use heavy-duty rubber or silicone spatulas with heavy-duty plastic handles. Many soapmakers use wood, but day-to-day contact with lye eats into the wood, and before long the utensils begin to splinter off into your solution.
Water is used as a solvent within the soapmaking process. To make soap, three molecules of alkali must react with one molecule of a neutral oil. Dry, caustic soda sprinkled over a mixture of just fats and oils would not come into contact with very many neutral oil molecules, and, in its undiluted form, the sodium hydroxide flakes would be too concentrated for neutralization to take place. Water, the universal solvent, dissolves the sodium hydroxide, carrying it to all corners of the pan. It increases the surface area of the sodium hydroxide, thereby ensuring thorough interaction with the neutral oils.
Water is the only chemically inert component in the soap-making reaction. Its job is to convert the caustic soda into a usable state, and then to sit tight. The oxygen and hydrogen atoms do not participate in the chemical equation — they remain bonded, as water, even within the final bars. They do not decompose and interact with the other compounds.
The key is to calculate the amount of water necessary to dissolve a specific amount of sodium hydroxide. Too little water won’t bring the soda into solution, causing the final soaps to be brittle and dry. Too much water will add unnecessary moisture to the soaps, making them less lasting and too soft. The right amount of water will dissolve the sodium hydroxide, transport it throughout the neutral oils, and add plasticity to the final soaps. Keep in mind that a formula is somewhat flexible with respect to the amount of water required to dissolve an amount of sodium hydroxide; acceptable amounts need not be exact, but rather fall within a range.
Though a soap formula will be somewhat forgiving, hard contaminated water will eventually surface as one defect or another. Hard water contains dissolved mineral salts which are quick to latch on to the sodium hydroxide ions, leaving fewer of the ions to react with the neutral oils. This dilution of the lye saps the solution of some of its strength. Not enough alkali will remain to saponify the full amount of fats and oils.
Test your tap water for softness and purchase distilled water if the results are less than encouraging. The quality of each individual component within your formula is directly related to the quality of your final soap. I occasionally use rainwater, though rainwater may contain many surprises; all sorts of impurities fall into the vessel along with the rain. A bug or two are sure to be floating on top, next to a pine needle, a leaf, and some other unknowns. Always strain fresh rainwater through a strainer lined with layers of cheesecloth.
AN APPRECIATION OF THE SOAPMAKING PROCESS
I sometimes think about those people of past centuries who couldn’t run out to the supermarket to buy lye cleanly packaged and ready to use. Just as I’m feeling blessed with convenient and superior products, I’m moved to think hard about those folks. Their lives must have been physically demanding ones, but I wonder whether their days offered greater spiritual rewards.
Once the sodium hydroxide has been weighed, carefully add it to the cold water and stir briskly. The fumes will overwhelm you within just ten to twenty seconds. I hold my breath until the beads are fairly well incorporated, and then I leave the room for fresh air. I return two minutes later to completely blend the mixture, being sure to incorporate any sediment which has settled on the bottom of the container.
Let the mixture sit for a couple of hours to cool down. For maximum solubility, be sure to incorporate all of the dry sodium hydroxide in the water while the solution is still very hot. As the solution cools, any excess flakes will harden in a clump on the bottom and make mixing more difficult.
Once cool, cover the lye solution until you are ready to use it. Long-term exposure to air weakens the solution through the formation of sodium carbonate, which forms when the sodium hydroxide combines with carbon dioxide in the air. While pouring the lye into the oils and fats, stir briskly until all of the lye is thoroughly incorporated. Since keeping the molecules in constant contact with one another is what makes soap, try to keep stirring briskly throughout the soapmaking process.
