Soapmaking Safety and How to Weigh Oils for a Batch of Soap

Two bars of handmade goat milk soap. Here's how to measure the oils and lye, and the safety precautions you'll need to follow.

Learn how to make goat milk soap in this six-part series on soapmaking. This post discusses the safety precautions you should use when making soap, including lye safety, and how to weigh oils for soapmaking. Here's how to make goat milk soap.

Goat Milk Soap: Safety precautions and weighing oils

Have you ever used a bar of handmade goat milk soap? I just can't tell you how superior it is to store-bought soap. 

Updated May 2022

The lather is thick, creamy and luxurious. The fat in the milk makes the soap extra-rich, and I use skin-nourishing oils. Everyone who has tried my soap loves it!

I'm going to show you my soapmaking process and give you tips that I've discovered and use myself, but I recommend that you read books and additional tutorials online. This is a case of the more education and knowledge you have, the better.

Getting several points of view will make the process more understandable and hopefully less scary. Making homemade soap is easy, but not simple. There's a lot to remember!

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 and entertainment purposes only.

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

Using sodium hydroxide (lye) in soap making

I talked about this in the first soap-making post in this series but I'm going to say it again: safety when making soap is extremely important

Lye is a caustic substance, and contact with skin or eyes will result in a nasty, painful, and permanent burn.

When using lye:

  • Always wear goggles and rubber gloves.
  • Always keep your focus on your soapmaking; do not be distracted. Do not attempt to make soap with children or pets in the room.
  • Always add the lye to the liquid, NEVER the other way around. I was taught to "add the lye to whatever" because the first step is to add it TO the milk or water, and the second step is to add the milk/lye or water/lye solution TO the oils.
  • Store lye where children and pets absolutely positively cannot get into it, preferably under lock and key.

I have a very healthy respect for lye, and so should you. I always wear safety equipment: goggles or safety glasses, a mask, and rubber gloves.

The safety equipment you need to make soap: gloves, safety glasses and a mask. Long-sleeved clothing and an apron are also recommended.

I talked about these and the other items you'll need to make soap in Part One of this series, which you can read here: Everything You Need to Make Goat Milk Soap.

You can also find these supplies and equipment in my Amazon storefront.

The trick to making soap with milk

Most people start out with water-based soaps. Making soap with milk is a bit trickier. 

I disregarded that wisdom and jumped right in to making milk soaps, and I've only made a water-based soap once or twice.

The trick to making soap with goat milk - or any milk - is to freeze the milk before you start. 

The heat of the lye burns the milk and turns it brown; using frozen milk helps keep the temperature lower, but I still end up with soap that ranges from cream to beige instead of the white I sometimes want. 

Each batch is a different shade and I can't predict the final color. I like to think that it depends partly on which goat produced the milk, since the amount of milk sugar and butterfat in milk varies from goat to goat.

The easiest way to freeze milk is in ice cube trays, but I usually end up pouring milk into quart-size freezer bags and freezing them flat. 

When I'm ready to make soap I hit the bag with a hammer to shatter the frozen milk into chunks. 

It's pretty easy to weigh out enough milk whether it's in cubes or chunks: I just add chunks till I'm near the correct weight, and swap one chunk for another that's either bigger or smaller depending on how much more or less I need.

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Soapmaking safety

All the utensils I use for soapmaking are never ever used for food preparation - my mixing bowls, plastic spoons, stick blender, and dishpan are used only for soapmaking, and are stored in my "soap studio" (a fancy name for our mudroom), not in my kitchen. 

I keep the lye and the empty margarine tub I use to measure it in a locked cabinet.

Before I use a new recipe or change a recipe I always run it through a lye calculator. 

I enter the amounts of the oils I'm using, and the calculator tells me how much lye and liquid to use. 

You can find lye calculators online at Soapmaking Friend and at Brambleberry, but there are others online as well. 

Don't skip this step when you make a new recipe, because typos can happen! 

Also, if I need 10 ounces of coconut oil but only have 8, I can substitute two ounces of another oil - but I have to use the lye calculator to see if I need to change the amount of lye. 

Each type of oil requires a specific amount of lye in order to turn it into soap, and that amount varies by the kind of oil you are using.

I set the superfat level in the lye calculator to 5% for milk soaps, and 6% for a recipe made with water or non-milk liquid. 

Soapmaking requires a certain amount of lye to turn fat and liquid into soap; this is what the lye calculator figures out for us. 

Most soapmakers like to have extra fat in the soap to make it extra-luxurious, and this is called "super fatting." There is no hard and fast rule about the percentage of superfat you should use, but 5-6% is pretty common. 

I use 5% because milk contains fat of its own, and I use 6% for non-milk soaps because water doesn't contain fat.

Use a good digital scale that weighs in grams to measure the oils, milk and lye you'll need to make goat milk soap.

How to weigh oils for a batch of soap

I've developed a "batch sheet" that I use for each batch of soap I make, so that I have the recipe printed out right in front of me.

This sheet keeps me organized as I measure the oils for my batch. I check off each one when it's been measured so I won't forget one!

I've made a printable soap batch sheet just like the one I use myself,
and I'll send to you for FREE.
Make as many copies as you need for your personal use.
Tell me where to send it in the form below.

Step One: weigh the frozen milk cubes or chunks on a digital scale. Analog scales aren't as accurate, and accuracy matters in making soap.

Step Two: weigh all the oils and butters in the recipe. My scale can be "zeroed out" by setting a bowl on top, pressing a button to set it back to zero, and then adding the oil to the desired weight. No subtraction needed!

After I weigh and measure each of the oils and butters, I add them together into two containers: one for the liquid oils such as olive and castor oil, and another for the solids such as lard, coconut oil, cocoa butter, etc.

If I don't have enough time to continue making soap today, this is where I stop, with all of my oils weighed into the two containers. 

I label the containers and put them in the refrigerator, or in the freezer for longer-term storage.

If you do this, label those containers very well. If you have containers for more than one batch of soap in your refrigerator or freezer, mark them so you'll know which two go together for each batch.

For instance:

  • Container #1 - "liquid oils for my regular goat milk soap recipe: olive oil, castor oil, sunflower oil. Batch #67"
  • Container #2 - "solid oils and fats for my regular goat milk soap: coconut oil, lard and tallow. Batch #67"

When measuring oils for soapmaking, measure the liquid oils into one container and the solid oils into another. This makes it easier to make goat milk soap.

Step Three: Before I start making the soap, I line my soap molds with freezer paper to make it easy to get the uncut loaf of soap out of the mold afterwards. 

Wax paper doesn't work, by the way, it must be freezer paper. Wax paper absorbs the oils and sticks to your soap in an awful way. Take my word for it.

Some say that lining a mold is only necessary if the mold is made of wood, but I love being able to pull the loaf of soap out of my silicon mold with such ease.

Step Four: Measuring the lye is the last thing I do, right before I'm ready to make soap. Even if I've measured the oils previously and put them in the refrigerator, I don't measure the lye until I'm ready to make soap.

I think it's safer to keep the lye in the original container until I'm ready to use it, and I keep my lye under lock and key for safety reasons. 

While I can measure the milk and the oils in a regular cereal bowl from my cupboard, I have a dedicated container used for measuring lye; it never goes in my dishes. 

Do not use a metal container to measure lye; it will react with the metal.

I use a plastic margarine tub with lid to hold the lye when I measure it, in the same way I measure oils. 

I put it on my scale, press the button to clear the scale back to zero, and measure the lye. The lid goes back on the margarine tub to keep it from spilling accidentally, and I set it on the counter next to the sink where I'll be making the soap.

Using frozen goat milk to make soap keeps the color of my soap lighter, but it always ranges from cream to light brown. These bars were made with frozen cream instead of milk and are lighter than my soap made with milk.

I've written LYE and FOR SOAP ONLY all over the margarine tub with a permanent Sharpie, and  it's only used for measuring lye. 

When not in use the tub is in the same place I keep the lye: in a locked cabinet. I'm taking no chances with this stuff. 

And maybe I'm wrong but I don't wash out the container, because I would be adding water to lye which is a big no-no! That's why I keep the lid on the empty container and store it under lock and key - because it does still have some lye residue in it.

You might want to use some other container to measure the lye; you know your situation much better than I do. Something disposable might be better, but be sure to dispose of it safely after use, where children and pets aren't likely to get into it.

Now that you've measured the frozen milk, the oils and the lye according to the recipe you're using, you're ready to get started. Keep your frozen, measured milk in the freezer until you're ready to actually start.

The next post in this series is How to Make Cold Process Soap with Goat Milk

All the posts in this soapmaking series are listed here in order.

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How to weigh oils to make goat milk soap, and a lesson in soapmaking safety.


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