Cold Process Soap

(and how we make it)

The Cold Process method of making soap is one of the oldest - however even today, most commercially produced soaps are made by hot process, or boiling. As the name implies, cold process soap is produced without boiling. In this process, saponification occurs using only the heat released by the conversion of the fatty acids in the oils into soap molecules. Temperature control is still needed as some of the base oils need to be warmed up because they are solid at room temperatures, but this process does not require boiling the soap mixture or "cooking" to produce soap.

The first step is selecting the base oils. Almost any vegetable or animal oil can be used, with varying results. Different oils also impart different characteristics to the finished soap, pertaining to cleansing properties, hardness, lather, conditioning, and so on. By selecting different oils and percentages in the base mix, we can tailor the soap in many ways. In our shop, we don't use any animal based oils.

The base mixture for most of our soaps is a blend of Olive, Palm, Coconut and Castor oils. This blend provides an outstanding balance of hardness, cleansing, and lather. Because we don't remove the glycerin that is naturally produced, our soaps are much more moisturizing than the commercial soaps you might buy at a supermarket. Our conditioning soaps also include Cocoa, Mango or Shea butter in addition to the base oil mix to add extra conditioning qualities. And of course our Classic Castile soap is made of 100% Olive oil.

Now that we have our oils ready, it is time to look at the other major ingredient - lye. Soap is actually a chemical salt of the base oils, and to produce this chemical action in soapmaking requires a caustic agent. Hard soaps, like our bars, use sodium hydroxide (also known as lye or caustic soda), while liquid soaps use potassium hydroxide. In either case, all of the caustic is consumed during the reaction and none of it remains in the finished soap. In fact, we set the proportions of lye and oils so that there is more oil than can possibly be reacted by the lye, to make sure that all of the lye is consumed. This is known as "superfatting".

There are many different schools of thought as to how and when colorants should be introduced. Some recommend that the colorant be pre-mixed with water or a base oil and then mixed in at trace, others suggest adding the colorant to the lye solution. While all these methods work, we have found that coloring the base oil just before saponification is very easy and gives us excellent results. Our soaps use only mineral pigments, such as oxides and ultramarines for color.

Mixing the oils and caustic is the next step. The lye is first diluted in distilled water to make it easier to mix. Because this is an exothermic reaction (it gets hot!), we need to juggle the temperatures of the causic and the oils so that they are about the same when they are mixed together. We also don't want them to be too hot or too cold - preferrably in the 110 degree F range. At this point we mix the two together and start to stir.

This stirring process mechanically mixes the caustic and the oils, casuing the oils to change into soap, or saponify. The more the mixture is stirred, the more the reaction takes place. In the old days, this was stirred by hand and took hours, but of course today we use powered mixers that reduces the effort and time considerably.

Once the saponification process starts, we observe the behavior of the mixture to determine when to introduce additives such as fragrances or colorants. The key indicator is called "trace" and refers to a thin pudding-like consistency where a bit of mixture drizzled back into the pot leaves a raised line on the surface. Continuing to mix after trace will yield more and more pronounced trace effects, along with thickening of the batter. If one were to keep on mixing, eventually the batter would become solid (seized) and would not be able to be poured into the mold. We generally stop at light or very light trace, depending on the particular soap we are making.

Now that our batter is at trace, it is time to add any other ingredients. Mainly this means the fragrance, although if we are making an exfoliant soap this is also the point where we would add the pumice, luffa or bamboo silk. Fragrances come in two main types - essential oils and fragrance oils. Essential oils are distilled from plants, and are completely natural. Aromatherapy is based on the use of essential oils, but these oils can also be used in bath products, perfumes and even candles. Our "All Natural" soaps use only essential oils for fragrance.

Fragrance oils differ from essential oils in that they also contain artificial fragrances. Fragrance oils are used extensively in perfumes, bath and beauty products. Because fragrance oils are not limited to plant products, there is a much wider variety of scents to choose from. However from a mixing point of view it doesn't matter which type of fragrance we use - once we reach trace, we fold in the fragrance and then pour the batter into the molds.

After the batter is poured into the molds, the mixture continues to react and saponify. Some varieties are then placed in a low temperature curing oven for a couple of hours, to assist in "gelling" the soap. While gelling is not required, it produces a slightly smoother finished soap. Other soaps, especially those containing fragrances with low flashpoints, are not gelled. After curing for two hours, the soap is allowed to cool to room temperature.

The next day, the soap is de-molded and cut into individual bars. Our molds produce loaves of soap, similar to a loaf of bread, and we cut them into bars using a wire slicer. This method ensures that each bar is the same thickness, and very close in weight.

At this point the saponification is complete, and the soap could be used. However it also still contains a lot of water and is very soft and easily damaged. So instead we place the individual bars on drying racks. The soap bars are then dryed for several weeks to a month or more, depending on variety. Castile soap is particularly soft due to the high Olive oil content, and needs the longest drying time. Once the bars are sufficiently dry, a sample from each batch is tested for ph level. Every bar is then weighed, visually inspected and then labelled, and is now ready for sale.