Side Projects

How to Make Soap

Steps to make soap:

Mix lye into water

Mix lye solution into liquid fat

Stir a lot until it begins to set

Pour into a container and let solidify

Cut into Bars

Thats it!

Like rendering fat, it really is that easy. Along those lines, I made a batch of soap today using the animal fat I rendered in a previous post. The one aspect of soapmaking I do suggest you overanalyze is how to handle lye safely. As long as you have protective gloves, 2 suitable containers for the lye to heat in, dedicated soap making utensils and take care not to come in direct contact with the lye, the dangers of lye will be minimalized!

Process in more detail:

Soap is made by a chemical reaction between lye and oils. Low pH of lye cleaves bonds in the oil forming fatty acid salts and glycerol. Resulting products from this reaction allow particles insoluble with water to become soluble, hence the cleaning action of soaps.

Fun Fact: Soap making was first recording in ancient Babylon in 2800 BC where basic (pH) salts were dissolved in water then mixed with an oil from a cinnamon tree. (Laughably expensive source).

What You Need:

For any utensils or tools, dedicate them to soap making. I don’t know if it is necessary, but I don’t prepare food with items exposed to lye!

Lye and protective gloves (I ordered this to get the gloves as well but I will explain how to make your own from wood ash soon!) Make sure it is pure lye and not chemical-laden drain openers. Hopefully meth-heads don’t ruin our consumer access to lye.

2 Thermometers that include 95 degrees F to 120 degrees (Nice instant digital example, analog example)

Fat, animal or vegetable (I harvested the tallow from a deer I hunted but you can use any oil or lard, suet, tallow or any other animal fat from a butcher as long as you render it)

2 Stainless Steel pots (I used one and transferred the lye solution to a pyrex container after it had cooled) (Something like this but I got mine at a thrift store. Just make sure it is not copper or aluminum coated on the inside)

Lye-safe stirring mechanism (thrifted wooden spoon for me, after you learn what “tracing” is, then try a cheap  hand mixer to speed it up)

Scale (this is the best one I have ever used. Also great for brewing beer and general kitchen use)

Ziplock bag to measure lye

Soap mold (can use any container: shoebox, old bread pan, cupcake tin, special shaped silicon soap molds, wooden molds, etc)

Parchment paper to line soap mold (wax paper or freezer paper work as well)

Rack for curing (rig something simple up that resembles this or any other kitchen cooling rack). Also you don’t have to worry much about lye contamination at the point these are used.


Electing to keep is simple as a first control batch, all that is required is lye and fat. Softened or distilled water is added to the lye to more evenly distribute it among the fat and make it easier to work with. Fragrances and extras can be used but were omitted for sake of simplicity and to have a product future ingredient additions can be built upon.

I took the lye to fat to water ratios in various publications, averaged them, then put them in an excel doc for easy scaling. Please disregard any recipe that uses volume measurements instead of mass. While I think people overthink these things, mass measurements will keep your product precise and replicable.

Makes about 4 pounds:

43 oz Fat

6 oz Lye

16.5 oz. Water


1. Completely dissolve the measured lye into the measured water (emphasis on order!) in a stainless steel pot stirring with glove-protected hands. It will heat up to 200 degrees Fahrenheit on its own! Also avoid directly breathing the lye fumes.

2. Place measured liquid fat into stainless steel pot. Apply heat to completely liquefy solid fats if needed.

3. When both fat and lye are at 95-115 fahrenheit, stir lye into completely liquid fat (emphasis on order!)

4. Stir mixture continuously until it traces. Tracing is when drops of the solution take a moment to disseminate back into the main body of the solution when dripped on top. This can take a while…with my all tallow recipe it took 20 minutes but some literature notes it can take up to an hour.

5. Pour soap solution into lined mold

6. Wrap mold in blankets/towels for insulation and let sit for 1-3 days

7. Remove loaf of soap from mold and cut into desired size bars. Let cure on a rack that gives airflow for another few weeks

Steps with Pictures

1. IMG_20150303_130747IMG_20150303_130809

2. Not pictured

3. Included in step 4 image

4. Very mild tracing is becoming evident. My solution went from color and consistency of broth to gravy to well-blended mashed potatoes to frosting in just over 20 minutes of stirring


5. I put the extra into cupcake papers. Note how the consistency continued to change (bottom to top) in the 2 minutes it took to pour the soap into them. The chemical reaction will continue to heat the mixture in the mold for 24 hours, hence the insulating blankets or towels, then continue at a very small scale for the 3-8 weeks it cures on racks.

IMG_20150303_143255 IMG_20150303_143425

6. IMG_20150303_164744

7. Coming in 8 weeks!

That’s it! Despite my tendency to over-adequately plan things, I feel like people seem to love to unnecessarily complicate things like this, and animal husbandry, and beekeeping and many others. Be precise in your measurements and smart in the lye handling. Otherwise use whatever fats you have available to you and experiment! I guarantee you that whatever soap you make will be vastly better than anything from the store and have a much lower environmental impact.

Don’t forget that this can be made into dish soap, laundry soap, etc. I will post about those when I have to restock my stores!


6 thoughts on “How to Make Soap

  1. Sounds great! Unfortunately, I don’t have the room for all the utensils but I bet my eczema would recede if I were able to make a soap as simple as this.

    Funnily enough I have been on the look out for a thermometer (for yoghurt-making) just today. No luck in the shops so looks like EBay is the next port of call 🙂


    • I understand the utensils issue. Ever since wanting to minimize my possessions it has been a balancing act of holding onto useful but space consuming stuff and deciding what I could fit in my desired tiny house (future). Beer making equipment is the bulkiest!

      If I recall correctly you are in the UK? I guess my products aren’t much help in that case :(. I’d be happy to send you some of the simple soap as long I’m not violating any international shipping policies!


      • That’s very kind of you! I am curious about the soap – if you would be happy to send me a piece of soap I wouldn’t say no.

        Anyway, yes I am in the UK but I can search on the UK version of Amazon for an appropriate thermometer 🙂


      • Helen, I was at the farm and not very attentive to technology. Sorry about that! After the soap cures, I’d be glad to send you a bar. Is it ok to send an email to the address you have registered to you wordpress account when the soap is ready?


  2. Pingback: Creating Potash aka Lye aka Potassium Carbonate from Wood Ash | thegreenergrassfarm

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s