If you've been to a market or pharmacy lately, you've probably noticed the sudden shortage of hand sanitizer, hand soap, and detergent. As a part of our collective efforts to confront COVID-19, we've all been stepping up our cleaning game, and the limits on supplies are a natural result.
The U.S. Centers for Disease Control recommend frequent hand washing with soap as one of the best possible defenses against the virus. Here's the basic approach to making your own soap at home.
The basic mixture required for common cleaning soap is some kind of fat or oil combined with an alkali like lye. There are many kinds of fats and oils, and the term lye has been applied to several different chemicals over the years (all the way back to its origins as wood ash thousands of years ago), so this combination isn't strictly technically controlled. The U.S. Food and Drug Administration defines soap as "composed mainly of the alkali salts of fatty acids," which are the ultimate result of combining an alkali with fats or oils.
Today, the word lye commonly refers to sodium hydroxide or potassium hydroxide in the context of cleaning agents (the two are similar, but require different ratios to other ingredients). Other kinds of lye have culinary uses, but the kinds in soap can be hazardous to ingest. Finished soap products should contain no lye, since the alkali will have combined with the other ingredients during the process, creating a new chemical structure.
Cleaning lye is very caustic in its concentrated form. It can burn holes in fabrics, badly injure skin, and cause severe hazard if inhaled. Proper protective gear and good ventilation of the work area is crucial for safety.
If you get lye on our skin, flush the affected area with vinegar immediately (applying water can worsen the problem), then apply a paste made from baking soda and purified water to neutralize the lye and soothe the burns. Always keep lye and other chemicals out of reach of children and pets.
Avoid using utensils or equipment made from aluminium, tin, chromium, zinc, magnesium, bronze, brass, or copper, as they may react with lye in ways that can be at worst dangerous and at least corrosive to your cookware.
Do not reuse any of the utensils or containers used for handling lye for any other purpose.
Hot Process Soap Making
Step 1 - Measure
In two separate metal bowls, measure out the prepared amounts of lye and purified water. Use your kitchen scale to make sure the proportions are correct. Different fats will interact with sodium hydroxide slightly differently, but the approximate ratios should be one part lye to 2.35 parts water to 6.75 parts fat.
As an example—one recipe calls for 20 ounces of lye, 41 ounces of coconut oil (heated to a liquid state), 47 ounces of olive oil, 47 ounces of palm oil, and 47 ounces of water.
Other ingredients like milk, coffee, oats, and various herbs can give your soap its own scents and textures, but the crucial ratios from a chemical perspective are the balance of your alkali and fats.
Step 2 - Stir the Lye into Water
Carefully and gradually, stir the lye into the water, and stir the mixture until the lye has completely dissolved. Never pour water directly onto lye, since the reaction can expand rapidly. Do not allow this caustic solution to spill, and take great care handling the bowl—the chemical reaction will make it hot to the touch.
Step 3 - Cool (optional)
You may wish to cool the lye solution beneath a ventilation fan while you prepare the rest of the ingredients. Some recipes call for combining them at similar temperatures, but the important part is that all the elements are in a liquid state when you mix them, since they need to be thoroughly combined.
Step 4 - Melt Fats and/or Oils
Measure out the fats and/or oils that you intend to use and place them in a cooking pot (one possibility is an old crockpot you won't be using for other cooking) then set it on low heat until they melt completely.
Step 5 - Mix
Add the lye solution to the other ingredients and stir them together well with a metal spoon. After the initial stirring, use a hand or stick blender to combine everything thoroughly for 5-10 minutes until the mixture reaches a consistency like pudding.
Step 6 - Cook
Cover, and let your soap cook on a low temperature for one hour. Resist the urge to stir it more by focusing on preparing your soap molds.
Step 7 - Prep Molds
You can choose from a wide variety of plain or fancy shapes if you're picking up some new molds, or use old cookware you're comfortable converting into soap-only equipment. If you choose something like a bread loaf pan, you may want to line it with parchment paper, if available.
Step 8 - Harden and Cure
Carefully spoon or ladle the mixture into the mold(s). Allow the soap to cool and harden for the next 24 hours before you remove it and (if it was in a large container) cut it into bath-sized bars.
If you can, store the bars somewhere cool and dry to harden a bit more—some recipes call for curing for up to a month. From a chemical standpoint, the soap is ready to use now, but it may be more crumbly or soft than you'd like.
Step 9 - Grate (Optional)
If you're going for a product you can use as detergent for laundry or dish washing, you can take a cheese grater to your product at this point to make flakes from the bars.
Step 10 - Clean, Label, and Store Equipment
All equipment that's been exposed to lye must be thoroughly rinsed and cleaned before any other use. For best safety practices, this should just become your soap making kit, and never work its way back into regular circulation.
Adding Moisturizer and Scent
Any standard soap will dry out your skin through repeated use. Adding moisturizers like Aloe vera can provide some protection. Other essential oils such as lavender or oil of camphor can add appealing scents, and some are reputed to have homeopathic qualities.
While your tinkering with your favorite recipes, you might take things a step further and use some herbs from your garden to make your own essential oils!