Volume – can you hear me now? 1

Today I am starting with volume. This word has many meanings in our daily lives. For our kids it means turning up the sound projection of the music. For people who work in purchasing it means a greater number of items for a lesser price per unit. For people who work in shipping it means taking the lion’s share of a freight truck trailer, rail container, or cargo ship container. For soapmakers it is much closer to the meaning used by shipping specialists.

Remember, we are talking about our favorite 4-letter word…. MATH.

Let’s be square. Sort of. Most bar soaps are cut in a rectangular prism shape. This means starting with a rectangle and adding one more measurement to take a 2-dimensional product to a 3-dimensional product. Rectangles are 2-dimensional, rectangular prisms are 3-dimensional. Isn’t this cool? It is hardly past breakfast time and you have already worked a new phrase into your vocabulary! The best thing so far is you don’t even need those silly glasses to see a 3-D rectangular prism! It is just right there! Cookies boxes, blue Kraft dinner boxes, shoe boxes and more, are all rectangular prisms.

Together we have taken the first step. We added words to our vocabulary and can see examples around us.

So….. Let’s calculate volume. Don’t panic. This is simple stuff here. If you can make ice then you can calculate volume. Don’t even think I will buy the story that you can’t make ice. I’ve heard of people claiming that only one person in the family can make ice and they go as far as taking the secret recipe to work with them. Well, I’m going to write the secret recipe right here so you can calculate volume any time you desire.

Length x width x height. Or height x length x width. Or width x length x height. It does NOT matter which order you put them in. Just get out the tape measure or ruler and take each measurement. L x W x H. Simple. Remember! Take the inside measurements!

Why do soapmakers need to know volume? Simple, how do we know the amount of soap a mold can hold? Volume. This calculation is important to soapmakers. Very important.

Have you ever called our office to ask how many bars are in a specific amount of soap? The answer is always “ONE, until you cut it.” Soap bars vary in size. Some of you make 2 ounce bars, some make 8 ounce bars. If two different makers have 8 ounces of soap then the 2 oz bar maker has 4 bars of soap and the 8 oz maker has 1 bar. The 2 ounce maker does NOT have more soap, just more bars of soap.

Are you ready to talk about molds? Most of you have questions about how much soap to make to fill your mold. If your soap mold is 2 inches deep you are NOT required to fill it to the top. If you want a 1 inch deep pour of soap then calculate the volume of the mold as 1 inch deep. The length and width of the soap are not easily changed so figure those numbers as set in stone. Deep, depth and height will mean the same thing when we are talking about soap molds. Length and width are the sides.

Here are the points to remember:

  • Length x Width x Height = Volume of a Rectangular Prism
  • To determine the volume of a potential mold measure the inside of the box and not the outside of the box.
  • Keep your unit of measure the same. Use inches or centimeters, it doesn’t matter. But DO NOT make the length centimeters and the width inches. No mixed Units of Measure!

I’m going to break today’s post into two. I think if I let you work through the information here then go forward it will help cement the idea that math is easy.


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About Tina

I started thesage.com in 1996 with the help of my husband. Now I get to help people make all kinds of soaps and bath and body products. I think my favorite things to make are lip balms and lotions/creams. Of course I get most of the soap technical support questions because that is my strong knowledge area. Glad this blog is here!

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One thought on “Volume – can you hear me now?

  • Cee

    So… I have a wooden wine box from the liquor store… used to ship wines. The inside measurements are:

    3.75” Wide X 13”Long X 2.5” High = 122” (rounded up)

    Now I know I don’t want to fill the mold all the way up because the box has a top , so I use 2.25” for the Height and I get:

    3.75” Wide X 13”Long X 2.25” High = 110” (rounded up)

    Now what? How do I figure the amount of oils (by weight) to fill 110” by volume?

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