Introduction

This recipe, or a similar one, makes the rounds annually as the weather warms.¹  It has nothing to do with soap or soap-making. except it shares a technique, and an effective if reductive simplicity.

It is possible to make soap by putting an appropriate alkali into a small jar, adding fat and shaking it: Malachy Postlethwayt noted this in his Universal Dictionary of Trade and Commerce.² The point to his remark, a somewhat cranky aside in his entry on soap, was to suggest the value of new technology to solve problems in the soap-making industry. Here, that tedium was the constant stirring required.

The first time I tried Postlethwayt’s recommendation this was the result:

Ice cream and soap-making may share a simplified mechanical description but they engage different chemical processes. In the recipe above, ice cream is a combination of sugar and flavoring in fat (cream). Agitation dissolves the sugar and spreads it, and any added flavoring, through the cream. Agitation also introduces air, which thickens the mixture—the volume increases. Lowering the temperature of the mixture maintains this expanded form and provides additional novelty to something that could be consumed with pleasure at room temperature.

Shaking melted fat or oil with a caustic (alkali) solution as Postlethwayt describes doesn’t dissolve one into the other.³ It does encourage a reaction, called saponification, in which the alkali, usually potassium or sodium hydroxide, breaks apart and combines with parts of the fat to form soap plus a liquid that, as Michel-Eugene Chevreul described, contains glycerin.

This is merely an introduction to my experiences with soap-making.

In part owing to Cheverul’s work, we think about the chemistry of soap-making in slightly different ways from that of many early modern descriptions. But Postlethwayt’s early, basic description is still viable and still common.

Characterizing soap

We are told:

• Fat + a strong base → saponification → soap
• The fat source for soap might be animal vegetable or mineral.⁴
• The outcome you can expect from your soap-making endeavor depends on the substances you use and the process you employ to encourage their combination. The soap-maker has considerable control over the material characteristics of the product.

A broad categorization of the choices of substance for soap-making are: solid or liquid fat, sometimes determined by its animal or vegetable origin; potassium hydroxide (potash) or sodium hydroxide (caustic soda); hot process or cold. The soap-maker also has a measure of control over scent, color, and shape—these characteristics may be connected to use.

In general, the combination of animal fat with potash yields a soft soap, similar, perhaps to the Gallic pomade Pliny describes.⁵ Seed oils—liquid fatty materials such as olive or rapeseed (canola) oil—plus caustic soda yield a harder soap. The saponified mixture of animal fat with caustic soda may be harder than that of animal fat and potash. Seed oils or animal-derived oils with potash might be softer than those made with soda. Even in the 18th century, soap made with olive oil and an alkali sourced from a salt-tolerant plant known as barilla was considered the best for many purposes. The Mediterranean or Iberian origins of both substances meant that soaps from Marseilles, Castille, Nablus and similar districts were part of a busy trade in that substance.

The goal of my soap-making ventures was not to create the best soap, luckily. I wanted to work with the process as a means to explore the materiality of its components as they enter and exit the process. I also want to explore the materiality of the process of soapmaking, if such a thing can be usefully described.⁶ Assuming we can talk about the materiality of a process, how much is it dependent on the substances  used, how much on the techinques, and how much on something else?

Soap-making today has do-it-yourself-ness connections similar to those I mentioned in my exploration of tea lights.  It is also a great middle-school-level science experiment, one that can demonstrate mixture, chemical combination and acid-base reactions with a tangible, familiar and potentially useful takeaway product.⁷

Part 1. Lard, Lye, and a Cold Process

My first effort at soap-making for this project involved lye and lard in process that did not require heating. I melted some lard, watching it shift from butter-hard and white to a translucent pale yellow liquid. I dissolved household lye in a small container of water. The dissolution was exothermic, as expected. I waited until the lye and the lard were the same temperature—50°C—and then began to stir the lye into the fat.

My technique was is to stir and stir and stir—until the liquid to begin to “trace” or thicken—and then stir some more, until the combination was as thick as whipped cream. At that point, I poured the mixture into the container designated my “soap mold” and let it sit for 24 hours. This didn’t seem to be enough time—the product was still very soft, and I wondered if the saponification reaction was complete. I did know, of course, that this is the way to make a soft soap.

This raises a question that isn’t as sophomoric as it may sound: when we talk about a quality such as hard or soft, who or what sets the standard? I don’t recall seeing descriptions in any guild or corporate regulations: in the early modern period this aspect of materiality seems to be understood through the combination of materials used and technique. Was it then based on personal experience, at least until the late 18th or 19th century, or later? What does this differentiation mean, when soaps lose water over time and so harden as they age?

After about a week of sitting, the soap was noticeably harder and had regained the off-white color of the melted fat; it smelled like lard but not overwhelmingly so. When wet, the soap became slippery and had a very low lather.

Part 1. Numbers

Lard (store purchased)            114 g
Lye                                                14 g
Water                                           36 g

Part 2. Canola Oil, Lye and a Cold Process

My second test also involved a cold process but used canola oil rather than lard.

Canola oil is not an animal fat, I know.⁸ I wanted a comparison and I wanted to find a good use for a large quantity of rapidly aging oil I found in my kitchen.

 I began as before, using approximately the same quantities of lye and fat. I heated the oil slightly, and combined the two liquids when they reached the same temperature.

I stirred the mixture continuously for about 7 minutes, but when it began to trace I walked away for several hours. Postlethwayt was correct, although I suspect the tedium he described does not scale up as the ingredients do. When I returned to examine the mixture, it had thickened without my attention. I added a few drops of almond oil and took up stirring again. After about 10 minutes, I left it again for about 24 hours. The next day it was considerably thicker, pulling away from the sides of the container. I turned it out onto waxed paper and then wrapped it in newsprint to absorb the considerable quantity of excess liquid. I changed the wrapping several times over the next week before declaring the soap “made.” Still, I let it sit for a few more weeks before testing it further.

The product was a yellow-beige color similar to the oil I had used. It had a waxy feeling but was harder than the product of the first experiment. The odor is more similar to canola oil than almond but I probably didn’t add enough of the latter. When wetted, the soap made more lather than my first sample. It was slippery, but then isn’t that a principle characteristic of most water + soap combinations?

Part 2. Numbers

Canola oil (probably rancid)       111 g
Lye                                                    20 g
Water                                               40 g

Part 3. Lard, Lye, and a Hot Pocess

I still had a lot of lard to work with and despite its generally-acknowledged superiority over other shortenings in pastry the overwhelming percentage of vegan and vegetarian dinner guests means I don’t tend to cook with or eat lard. so, in addition to my soapmaking goal, a purpose of my third effort was to use up the remaining lard. I melted what I had in my soap-making pot and added to it solutions of lye and table salt, stirring carefully over heat until it thickened enough to pour into the soap mold.

The product was very hard and very white. It looked like ricotta salata, rather than the cookie dough resemblance of the earlier trials, including Part 1 (which used the same ingredients in a cold process). I did find I had to prime the soap with a considerable quantity of water before it began to lather. And, as with the other samples, I felt as if a residue—like a skin cream—remained on my hands after washing.⁹

Part 3. Numbers

Lard                                     200 g
Lye                                         28 g
Table salt                              28 g
Water                                    80 g

Part 4.  My Tallow, Lye, and a Hot Process Vriation

My months of collecting fat and kitchenstuff did not yield much, but it was more than I cared to cook with or make into tea lights. I used a portion—185g—to make soap using a hot process similar to that of Part 3.  I modified the effort with some new equipment—an electric hotpot. I hoped this would hold the materials at a steady temperature even in my absence, and that this might substitute for the constant agitation, at least until the soap began to trace.¹⁰

I began as before, by melting the fat. When I removed the tallow from its storage spot in my freezer, it was a dull white color with a few bits of something at the bottom of the jar. Once melted, the tallow was a deeper transparent yellow color and emitted a stronger beefy odor. I probably should have re-rendered it before using, but I didn’t. Undaunted by the odor, I dissolved lye and washing soda in water and added this caustic solution to the fat, stirred it, set the hotpot to low and yes, walked away.

After about 30 minutes there was a white foamy something at the top, not dissimilar to the white foamy what is it I found in my explorations of Chevreul’s experiments. This may be an outcome of heating without constant stirring; perhaps that’s something to explore in a later trial. I did then stir the contents of the pot, to see if this foam dissolved. Two hours later, the foam had turned into curds and sunk slightly; I stirred again, then added table salt. The quantity? Unmeasured.

Four hours later, the curds had risen to the top, and the pH of the liquid was about 13. After another hour of constant heating, I turned the hot pot thermometer to its lowest setting and left it overnight.

The next morning I stirred the solution again; the pH of the liquid had dropped slightly. I turned off the heat and left the container to cool. A few hours later I strained out the curds and washed them with cold water. The liquid I collected was now just slightly basic. The washed curds were hard and whitish and soapy-feeling.

While the curds were draining I cleaned the hot pot.  I put the soap back into it and added an unmeasured quantity of water, turning the heat to low: my goal was to melt the curds and make a cohesive soap. This required about 90 minutes and several bouts of stirring and curd-mashing. Once it was a reasonably cohesive liquid, I poured the soap into a mold and let it set for about a week.

The product is white with a waxy-feeling and a faint odor of the original tallow. It is soft but hardened and darkened in color with time. When wet it produces a good lather.

Several days later I remelted most of this soap, added lemon juice and lemon rind and some fresh and dried ginger. These are frequently-recommended additions to soap I came across in several compendia. The color of the soap became more yellow and it did smell more lemony than beefy. After a year of “resting,” however, it had darkened to a light brown shade and hardened on the surface. Cutting into the cake I found it was still waxy-feeling inside but the lemon odor was gone.

Part 4. Numbers

Tallow                185 g
Lye                     100 g
Washing soda    25 g (sodium carbonate, added out of curiosity)
Table salt            20 g
Water                 600 ml

Part 5. Shaken, Not Stirred

Malachy Postlethwayt, in his Universal Dictionary of Commerce article on soap suggested shaking ½ pint of the soap-boiler’s strongest lye (capital lye) with 1 ounce or more of olive oil for “half a quarter of an hour.”¹¹ When the solution rests, a solid cake of “tolerable soap” forms at the top of the liquor which, Postlethwayt promises, will harden on exposure to air.

So that is what I did. I dissolved 10g lye in 100ml water, added 30g of canola oil, shook the jar for seven minutes and then let it settle for an hour. As it was still very soft I added an unmeasured quantity of very old ground clove, shook for five minutes then let sit for three hours. I strained the contents of the jar to collect the curds, washed them in cold water and pressed them into a rough ball to dry. The point of the clove was not to congeal the solution, but to scent it and, perhaps add to its medicinal properties.

The result was beige-colored curds that remained very soft even after two weeks of drying. Its odor is slightly clove-like but more canola-oil-ish. When wet it fell apart.

Part 5. Numbers

Canola oil          30 g
Lye                      10 g
Water                100 ml
Clove                     1 g (approximately)

Observations

The process of soapmaking is not difficult to follow if producing a quantity of some thing is what matters. It became ever-clearer (as if I didn’t already know) that results depend on more than the materials you choose to work with. Time, timings, and and tools are also important. In short, soap-making is a skilled process but one that can be adapted to the less-skilled, or in which proficiency can come with time and experience.

I tested all the soaps in my kitchen and household cleaning for several weeks, keeping track (more or less) of which variety I used. The plain soaps were very harsh, making my skin noticeably rougher after less than a week’s regular use. Additions such as clove or lemon seemed to ease the effect. The hardened soaps are harder than a bar of commercially-available laundry soap such as Fels Naptha; they are soaps made to last.

Whichever I used, the experience of washing something with these soaps was different from that with modern commercial soaps. It was not simply that the soaps had to be very wet to produce a lather: all would be considered low-sudsing on today’s scales. In artificially hardened water none produced any lather at all. That’s not a great surprise. Lather is an aspect of the materiality of modern soap that indicates cleaning power; in truth it only indicates where the soap is. When using my own soaps, I relied on slickness of the soap’s surface and its shrinking size to suggest cleaning was taking place, but not necessarily an indication of cleanliness. It took a while to adjust to the feeling of something left behind on my skin, to not want to wash my hands after washing my hands.

Coda: 2023. The essay is published and I am sick of running into caches of handmade soap, all carefully labeled. I take them all, toss them into the hot pot, add water, and let them melt. I add a little rose oil. Well, actually, I add a lot of rose oil. I pour this dissolved soap mixture into a mold, let it set, score it into squares, and then let it dry for five weeks. Then another two weeks. The result: Old-cream yellow colored bars, mini-bars and odd scraps, smelling equally of handmade soap and roses. Contact me here if you’d like one.