Soaping Procedures

getting a feel for the steps involved in soapmaking…

© 2010 by KV5R — Rev. Nov. 24, 2010.

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Process Overview

The following is not a cast-in-stone procedure, just something to give you an idea of the steps you can expect in soap making. Please note the common-sense safety measures, like making caustic solution with the cup already in the wet sink, capping the lye container quickly, and dropping anything with caustic on it straight into the sink water.

Cold-process soap making works about like this:

  1. Design your recipe with a soaping spreadsheet or an on-line soap calculator.
  2. Collect your soapmaking tools and supplies (see the Tools and Supplies page).
  3. Set up your workspace and safety equipment (see the Soaping Safety page).
  4. Weight each of your oils into the mixing pot on a digital scale.
  5. Weigh the cold water and then set Pyrex cup in the sink. Fill sink to same level. Make sure the cup doesn’t float and turn over. A saucer under it keeps it from tipping into the drain. The water weight is not critical and should be between 2.33 and 2.0 times the dry lye weight, making a 30% to 33% caustic solution. Recipes calling for “full water” usually mean 27% caustic (lye weight × 2.7 = water weight).

    Making stronger caustic, called “water discounting,” may be used with soft oils, and will speed up reaction and cure times. The formula for making a certain percentage n% is: NaOH weight ÷ n% × (100 - n%) = water weight. Accepted range is about 27% for hard oils, to 45% for soft oils, with 30-33% being common.

    water in cup in water in sink
  6. Weighing the lye powder on the digital scale: Make sure the container is tightly capped, then give it a vigorous shake to break up any clumps so it’ll flow smoothly, else a big clump will pop out and knock lye everywhere. Make sure to tare the bowl first. Make sure the bowl, and your hands, are 100% dry. When pouring the lye powder into the weighing bowl, tap that last 1/10th-ounce (or gram) out very slowly, then immediately cap the lye container tightly before setting it down. Or just go ahead and leave it open, knock it over with the blender cord, and destroy your kitchen… If you weight out too much, simply use a dry spoon to put some back, working over the sink water (you willdrop some). Watch out for static cling.

    Spills: Make sure to read this topic on the safety page.

    weighing the lye
  7. Slowly add the lye powder to the cold (<60°F) water, then put the bowl in the sink, then mix the caustic with a stainless or plastic spoon ’til it all dissolves, then put the spoon in the sink. This is when the caustic may get hot and make fumes for a few seconds. Make sure ventilation is moving air away from your face, not toward you (see Safety page). If it fumes excessively, start with colder water next time. You can weigh your water first and pop it in the freezer while you weigh your oils.

    Exposure: Make sure to read this topic on the safety page.

    pouring lye into water mixing the lye
  8. Heat the oils to around 115°F (46°C) to melt and mix the solid fats with the soft oils. If using lard, weigh it into a bowl and microwave it (~30 seconds) or until its clear and liquid.
  9. Keep checking temperatures until both oil and caustic are about 100°F (38°C). They should not be more than 10°F (5.5°C) apart when mixing. If oil cools before caustic, put a low fire under it briefly. If caustic is cooling faster than the oil, take mixing cup out of the sink water (carefully). When checking temps, stir slowly with the thermometer. Then:
  10. Carefully pour the caustic solution into the oil. Don’t splash or drip! Put empty caustic cup into sink water. Add more sink water if needed to cover it.
  11. Start mixing with the stick blender. Hold it at a a slight angle, so the mix rolls from bottom to top, instead of just spinning. Keep it moving around. Remember to alternate blending and stirring. How long? It depends on the temperature and the oils used. Let’s say between 1 and 10 minutes (or hours if stirring by hand).

    Why is a stick blender so much faster? Because the caustic is in water, which doesn’t want to mix with oil. The high speed of the stick blender’s blade gets the water/oil finely mixed in a big hurry, putting the caustic in contact with the oil by vastly increasing the interface area between them.

    Don’t overheat the motor! Alternately blend and stir. Keep the blender near the bottom, and don’t lift it while it’s running—you don’t want to fling oil and caustic, and you don’t want to whip any air into the mix.
  12. When it barely starts to thicken (“light trace”), add scent oil, exfoliants (oatmeal, etc), and colorings as described in the recipe.
  13. When it thickens to almost the consistency of gravy (“full trace,” the surface will hold a dropped glob or stirred swirl for several seconds),
    1. The reaction is happening—work quickly here.
    2. Unplug stick blender, remove blade assembly from motor and drop the blade part in sink water.
    3. Pour mix into mold. Scrape out pot with rubber cake spatula. Drop spatula in sink water.
  14. Cover the mold with cling wrap or freezer paper, smooth the surface, and wrap it in a big towel (or better, make a polyiso insulation box).
  15. Clean up everything with dish soap and hot water. The fresh soap is still caustic—use gloves, else chap hands. A “bug scrubber” sponge gets the goop loose. Rinse well. Large stock pots are better washed outdoors or in the bathtub. Note that if you use any plastic or wood containers or tools, they should be marked and dedicated to soaping only, as they may absorb soap chemicals and flavors.
  16. Wait ’til tomorrow. Really. If you un-mold and cut it while the center is still in gel phase, you’ll likely ruin the batch and make a mess.
  17. Remove from mold. If it’s stuck, put it in the freezer for a while. The better wooden loaf molds are held together with wing-nuts and simply disassemble from around the soap. Slice and trim with a cleaver (use a miter box for straight cuts). If using a plastic cavity mold, follow its directions carefully to avoid damaging it when removing soaps. This is usually 30 minutes in the freezer, followed by running hot tap water over the bottom of the mold.
  18. Record the date and weight of your soap right after unmolding and trimming. This will allow you to weigh it again later and see how much water it has lost during curing. “Cured” is when the water content is under 5% of the total batch weight.
  19. Set the bars in a warm, ventilated place to cure for several weeks. Make sure all six sides are getting air (set them on wire rack). Curing is when the water slowly dries out of the soap. Since the water is still holding a little caustic, curing brings the remainder of the caustic into contact with fats, finishing the reaction. The longer the cure, the milder the soap—but don’t cure it so long that it goes rancid. Four weeks is a widely-accepted minimum cure time.

As you can see, I like to work over sink water, to receive any dropped lye and spilled caustic, and each item that touches caustic. That way, you don’t get caustic on surfaces where it can get on you. Work in and over the sink as much as possible, when handling caustic solution and freshly mixed soap.

Writing out the process makes it sound more complicated than it really is. You can make and pour a small batch like this in about 30 minutes.

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