Making Soap with Goat Milk: Cold Process

How to make soap with goat milk using the cold process method.

I've been making goat milk soap for almost ten years so it's second nature to me now, but I remember how scary it was the first time I made it.

Once again, let's get the legal stuff out of the way first:

These are the safety procedures I use.
Please note that I am not responsible for accidents;
this post is for educational purposes only.

This post contains affiliate links. Read my full disclosure here.

In an earlier post (How to Measure Oils for Soapmaking) I weighed the oils I'll use in my soap, weighed the frozen milk, and lined my silicon mold (affiliate link) with freezer paper (affiliate link) so it will be easy to get the finished soap out. 

There are two methods of making soap, called "cold process" and "hot process." Both processes begin the same, and that's the part we'll do today - this is how I make cold process soap. Yes, believe it or not, you must make cold process soap before you make hot process soap. (Personally, I like the finished cold process soap better. I'm not sure why hot process soap is so much more popular. Perhaps because it doesn't have to cure as long?)

I assemble my two containers of measured oils. I cover the countertop with several layers of newspaper to protect the surface. I get out my tools: mixing spoons, immersion blender (affiliate link), and plastic mixing bowls. I also get the zipper bag of weighed milk out of the freezer and the lye out of the cupboard.

My rule is to not make soap with children or pets in the room, and to focus only on my soapmaking. I don't have children at home anymore, but I do have dogs and cats in the house. The dogs go in their crates and the cats are "put in time out" in another room. I don't answer my phone if it rings or buzzes or makes any other notification noise.

Be careful when you make soap. Here is the safety equipment you'll need: goggles, gloves and mask.

I don an apron and my goggles, rubber gloves and mask (affiliate links). Hubby says I look like a mad scientist.

Weigh the lye

Next I weigh the amount of lye I'll need. I weigh it in an old margarine tub that is well-labeled, and set it next to the sink with the lid on.

Warm the oils

I weighed the liquid oils into one container and the solids such as tallow, lard and coconut oil into another. Do you remember I said in my previous post that lye burns the milk sugar and turns the soap brown? This is why I use frozen milk and why I keep the two kinds of oil separate: to keep things as cool as possible: to keep the browning to a minimum.

How to make soap with goat milk using the cold process method.﻿

I warm up the solid oils and butters in a saucepan until they melt and liquify, then pour them in the larger of my mixing bowls. I add the room temperature liquid oils (olive oil, etc) to the melted oils. The room temperature oils help to cool the heated oils a bit. I pour this whole mixture into the dishpan in my sink. Having the dishpan set inside the sink puts it at a comfortable level for me to work, and it also keeps everything stable and less likely to topple or slip or suffer some other calamity.

Add the lye to the milk

The frozen milk goes into my smaller mixing bowl and I sprinkle the lye on top, then put the lid back on the tub the lye was in and set it aside. I don't leave an open container of lye sitting around, even if the container is empty.


Remember, you must always add lye TO the liquid. Adding liquid to lye will cause an eruption of caustic lye that can be very dangerous.


Using my mixing spoon I carefully stir the lye and frozen chunks of milk. The heat of the lye will melt the milk. Keep stirring until all of the frozen milk has melted. I love these old Rubbermaid bowls with pour spouts because I can hold onto the handle while stirring; I found them at a thrift store. If you aren't lucky enough to find some at a thrift store, these batter bowls from Amazon are very similar (affiliate link).

Add the lye/milk to the oil

I slowly add the lye/milk mixture into the oils, stirring as I go. (Again, add the lye mixture TO the oils.) Stir gently so the lye mixture doesn't splash around.


If I were making a water-based soap, the directions would say to let the lye/water and the oils cool to the same temperature before combining. Because I'm using milk, I skip that step and add the lye/milk to the oils regardless of their differing temperatures.


... and stir and stir and stir. Using an immersion blender helps this step go a bit faster.


I alternate between using the stick blender and stirring with my mixing spoon. I don't want to burn out the motor on the blender. I'm careful to keep the blender submerged when it's turned on so the raw soap doesn't splash or spurt.


Bring the mixture to "trace"

The goal is to bring the mixture to "trace". Eventually you'll notice that the color has changed, instead of being transparent it changed to translucent and then became opaque. It will begin to thicken after awhile. "Trace" is kind of hard to explain. Let's see, it's thick enough that when you pick up the spoon, the liquid soap that falls off doesn't immediately disappear into the rest, it sort of sits on top of the surface. Or you can drag the spoon through the soap and a line will remain visible.

How long does it take for the soap to reach trace? It's different every time, and it depends on the room temperature as well as the temperature of the ingredients and even on the type of oils you are using. Just keep stirring and blending until it's thick.

How thick? I tend to take mine to a thick or medium trace. Some soapmakers like a light trace that is much thinner than mine. There's a bit of leeway here. It's easier to tell a heavy trace from a light trace.


This is where cold process and hot process part ways.

I prefer cold process soap. It looks smoother when it's finished and the color is lighter. Hot processed raw soap is much thicker; the difference is like cake batter (cold process) and a stiff mashed potato consistency (hot process). I think the cold process method is much easier too, but hot process is quite popular, probably because the curing time isn't as long.

This batch is cold process, so at this point I simply pour the soap into my mold, use my mixing spoon to scrape out the dishpan, cover the mold with a piece of paper to keep dust out, and walk away. I leave it undisturbed for 24-48 hours, then unmold it and let it set for another 24 hours or so before cutting. I do this in the mudroom, where I can close the door and not worry about the cats getting into the raw soap on my workbench or dog hair landing in it.

Clean up

Because I don't have small children anymore, I just put all my soap-covered utensils and bowls and tools (my immersion blender comes apart so I can put the electrical part away) into the dishpan while still wearing my protective goggles and gloves, stick the whole thing in a garbage bag, twist it closed and clip it with a clothespin or binder clip. I set it on the highest shelf in the mudroom, and leave it until the next day. By then, the soap has completely saponified and it isn't caustic anymore - it's soap instead of caustic lye and oils and milk.

Then I put it all in the kitchen sink, fill the dishpan with water and let it all soak for a bit, then I wash everything. I don't have to wear rubber gloves at this point. No need to add dish soap, because the newly-made soap I'm washing off of my utensils will do the job just fine.

If you have children at home, you'd probably want to clean it all up instead of leaving it on a shelf unwashed. I'll let you research the best way to do that since I haven't done it myself. Be sure you're still wearing your rubber gloves when you clean up.


We'll unmold, cut and cure the soap in another post, but here's a sneak peek at my finished cold process bars.


In this series:
Basic Equipment You'll Need to Start Making Soap
How to Measure Soap Oils and Safety Procedures
Soapmaking: Cold Process
Soapmaking: Hot Process
Soapmaking: Unmolding, Cutting and Curing

If you've ever used goat milk soap, you know how luxurious it is. Here's how to make your own using the cold process method.



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  1. Thank you, Kathi! Reading your soap making posts have become part of my research.


  2. Kathi at Oak Hill Homestead7:44 PM

    I hope it helps, Fern.

  3. I didn't realize the work that goes into soap making! What a loving and rewarding art!

  4. Kathi at Oak Hill Homestead6:31 AM

    Hi AnnMarie - it's funny, getting ready to make the soap takes a lot longer than the actual making of it. Thank you for your comment.

  5. Hi Kathi, I had a couple of questions. I've used goat milk soap that is soft and disappears quickly and some that is harder and lasts a lot longer. Does the tracing or the hot/cold process have anything to do with the lasting power of the soap? (Obviously, I don't know the language to soap making at all. But I'll need to learn next year when we finally start milking our goats.) Thanks for the tutorial, I'm pinning for next year!

  6. Kathi at Oak Hill Homestead7:44 AM

    Hi Jennifer. Those are great questions! I'll go into some of them more in Part Four (I started writing about soap and just couldn't stop!)

    How long soap lasts depends on several things. While some soapmakers make vegan soaps using only plant-based oils, I use beef tallow in my soaps which makes a harder soap. Also, the longer you let soap cure after making it the harder it will be and the longer it will last. And finally, be sure to keep your soap dry - don't let it sit in a puddle of water between uses.

    I haven't noticed if there's a difference in how well hot vs cold process soap lasts. I don't usually make hot process so I don't have enough experience to know. It's an interesting question.

    Hope you have a great weekend.

  7. Thanks Kathi! I'll be looking for your next two parts. I can't wait to start making my own soap.

  8. Kathi at Oak Hill Homestead6:13 PM

    You're very welcome, Jennifer.

  9. Thanks for this great post, it has made me want to make milk soap very soon. I can't wait to see the next installment. Thanks for sharing at Good Morning Mondays. Blessings

  10. Kathy, great post.
    I was wondering about your mold. The Milk soap making book I have stated that loaf molds do not work well with milk soaps, but obviously, you have had success with the loaf molds.
    Good to know.

  11. Kathi at Oak Hill Homestead6:05 AM

    How interesting, Sandra. I'm glad I didn't read that before I started; I probably wouldn't have tried it. Loaf molds work just fine. Perhaps using what I call a sheet mold (a big square mold) would keep the soap cooler and help preserve the color? The only problem I've had is with hot process soap if I don't get all the air bubbles out because it's so thick. I ended up with holes in my soap more than once.

  12. Again, you have taught me something new! I wish I could spend a week following you around, learning soap making (and everything else you do!) Thank you so much for sharing at the (mis)Adventures Monday Blog Hop.

  13. Kathi at Oak Hill Homestead10:17 PM

    Wow, I'd love to have some help. You're welcome any time! :-) Thank you!

  14. Hi Kathi, thanks for this super-helpful tutorial on making goat's milk soap (cold process). I've tried making goats milk soap before, but with less then satisfactory results. Your tutorial made it super-easy, leaving the goats' milk frozen. Plus,I like how you did the stirring in the sink. I felt more secure doing it that way then on the stove.
    I just used your tutorial and made a 2 pound loaf - it is now beginning it's cure out in the garage.
    Aaa and, I am going to use my husband's miter box to slice the soap when it is ready-- as you mentioned in your post. What a great idea! I have never been able to slice a straight line :-)

  15. Kathi at Oak Hill Homestead12:49 PM

    Yay, Mary!!!! You did it! I'm glad there were a couple of good tips in there that you found helpful. The miter box makes cutting so easy. Woohoo on your first successful batch!!

    (I like stirring it in the sink because, not only is it more secure and I don't have to worry so much about spills or splatters, it's the right height for me.)

  16. Thank you for all the information! One quick question, at what temp to the oils need to be before adding the lye?

    1. That's a good question, Lena. Most sources will tell you to wait until the oils and the lye/liquid are the same temperature. And while it's important to follow all the soapmaking rules, it's different when you use milk as your liquid.

      I use frozen milk so that the lye won't burn the sugar in the milk and turn my soap orange or deep brown. The person who taught me this always mixed her oils with the lye/liquid as soon as the lye had warmed up the frozen liquid and there were no visible frozen lumps left, so that's how I've always done it: as soon as the lye and milk are completely mixed, I add it to the oils.

  17. Hi! I'm actually wondering a about your clean up! When you say that you put the mixer, spoons, etc all in the mixing bowl that you used and put in a plastic sealed bag until the next day, isnt it hardened? How do you clean all the hardened soap off of everything? Thanks!

    1. Good question, Jeanine. Yes, the soap hardens on all of the utensils/tools. When I clean it all up the next day, I fill the mixing bowl with hot water and add the utensils to soak. The hardened soap is just SOAP at this point, and it softens and partially dissolves in the hot water, and after half an hour or so I can wash everything up easily. Any hard clumps of the soap can be scratched off with a fingernail and washed with a sponge as usual.

