Making Cold Process Soap – Basic Instructions

Cold process soapmaking is fun, rewarding, and a little bit scary. After all, working with lye can do some serious damage to you or someone else if you’re not careful.

Rather than write out the instructions for making soap on every single recipe on this site, I am creating this basic step by step guide. This guide is not intended to be a comprehensive lesson in soapmaking, but rather a basic refresher for the steps.

Since cold process soap making can be dangerous, my best advice is to take a class, learn from an experienced soapmaker, or read a good book. Once you do so, here is my technique that I learned from a friend (who learned from a class…).

Safety First:

  • Make soap when you are not rushed, and have no pets or children underfoot
  • Work in a well ventilated space
  • Wear a face mask, eye goggles, gloves, and a long sleeved shirt and pants. Minimize exposed skin.
  • Run your recipe through a lye calculator to verify you have accurate amounts. Two options are and Brambleberry. Always weigh your ingredients, do not measure by volume.
  • Don’t breathe in the fumes of the lye water
  • Cover any workspaces that could get damaged
  • ALWAYS ADD LYE TO WATER, do NOT add water to the lye. So important I will repeat it, slowly add your lye TO WATER.
  • Have everything you need (supplies, ingredients and tools) ready to go

Tools & Equipment:

1 container for making the soap in, you can also heat your oils in this container

1 container for mixing the lye and water. Both of these containers should be heatproof.

Digital Scale, to the 100th decimal place if you work in small batches (e.g. 0.00)

Stick/Immersion blender


Spatula—I use a flexible silicone one


Measuring containers and pipettes

Paper cup for measuring lye

Optional: Shot glass to hold your fragrance

Note: Do not use aluminum pans, bowls or equipment when making soap as it reacts with the lye.

I use an 8 cup glass pyrex container for my oils and to make soap in. I also use a 2 cup glass pyrex container for my lye water. I place the lye water container in another bowl in my sink. I have heard stories of the heat generated causing the pyrex to shatter so I want to make sure if this happens the spill is contained as much as possible.

Once you have used these tools for soapmaking, they should not be used for food anymore. I bought a lot of my soapmaking dishes and utensils at the thrift shop.

Getting Ready:

Prepare your molds as needed—I use a wooden mold and line it with parchment paper or with a silicone insert. Whatever type of mold you use, have it ready to fill.

TIP: I place mine on an unfolded towel so I don’t have to move it once I have poured my soap. I just wrap it up like a teapot in a tea cozy and let it set.

Ensure all of your containers and equipment are sanitary. Rinse them with some isopropyl alcohol or vodka and allow to air dry.

Weigh out your oils, lye and water.  Always measure your ingredients by weight.

I like to use a paper cup to measure lye in, as afterwards I can just dispose of it.

Now, let’s make soap:

Don all of your safety gear—glasses, gloves, etc.

  • Measure out your water into the container you are using for lye water. As noted in the tools section above, place the container for your lye water inside another bowl and then in your sink—I use my laundry room sink to make soap in as it is nice and deep in case of splatters. Sprinkle the lye granules slowly into the water, gently stirring until dissolved. Try to avoid moving or handling the lye container as much as possible.

TIP: I find the lye takes longer to cool than the oils to heat, so I always start it first.

  • Begin heating your oils on the stovetop or in the microwave. If you use the microwave, heat in 30 second bursts until the solid oils, butters, or waxes in your recipe are nearly melted. Reduce the time intervals and/or power as you get closer to temperature to avoid hot oil sputtering all over your microwave. You are aiming for 110-120 F.
  • Allow both your oils and your lye water to come to a temperature between 100-120 F. They don’t need to be exactly the same temperature, but should be pretty close.
  • Working in your sink or other workspace, slowly pour the lye water into your oils, gently stirring with a whisk as you do so. Stir for 30 seconds or so.
  • Place the stick blender all the way under the surface (IMPORTANT) and then start the blender, gently moving it around for about 30 seconds. Keep it submerged at all times to avoid spatters. Stop the blender, then lift it out of the soap batter. Whisk for 30 seconds. Then use the blender again. Continue to alternate whisking and blending until you achieve light trace.  The whisking helps to incorporate the mixture from the edges, while the stick blender accelerates the process of getting to trace. Once again, never start or stop the stick blender unless it is fully submerged.
  • Light trace is achieved when you lift some soap batter up with your whisk or blender and the drippings leave a mark or trail on the surface of the batter.  Your soap will have a soft pudding like consistency.
  • Add your fragrance and any other additives such as exfoliants, colors, etc. Stir in completely with the whisk or spatula.
  • Pour your soap into the prepared molds. Use your spatula to scrape out as much as possible (this will make cleaning your bowl easier). A silicone spatula works great for this. Place the lid on your mold, if you have one.
  • Wrap your mold in a towel and allow it to sit in a warm place for 24-48 hours. Avoid the temptation to peek.
  • After 24-48 hours, unmold the soap and allow it to continue to set for another 24-48 hours. After this you can slice it into bars.
  • Allow the bars to continue to set and cure for another 6 weeks before using the soap.

Clean Up:

It is best to let the leftover soap set in your soapmaking container for a day or two. This way you don’t pour raw soap down the drain, which isn’t great for drains. To make cleanup easier, I make sure to try to scrape out as much soap as possible, and I fill the container with water so the soap doesn’t dry out.

Wash all of your equipment thoroughly, then patiently wait for you soap to cure so you can enjoy it!!


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