Math, Math and the Math when Making Lotions from Scratch - Part 4 of 4
When we talk about the math most of us stand back and wait for someone else to calculate for us. It is much easier to use a recipe that has it all calculated, but if you are wanting to make a specific amount of jars of cream then you will need to do some math in order to make the amount you require.
Before I begin….
When it comes to technical support questions, percentage will rank high among the queries we receive. The very first thing from the makers’ mouth will be “I hate math…” or “I never was any good at math…” The first thing that needs to happen is a perspective adjustment. Math is not hard, it is not frightening and WE will not let you fail. Please trust us in this area and go forward with great expectations that you can succeed.
Percentage, or %
This very small symbol causes a lot of confusion when it comes to math. Simple math is something that most people do every day, such as being able to count one dollar by pennies. 1 percent of $1.00 is $0.01, or 1%. This small trick has helped me teach many people how to convert simple percentages into units of measure that make sense on any calculator. Anytime you see a percentage sign (%) then move a decimal two places to the LEFT and remove the symbol, there are two little “o” portions to that symbol so this should make it easy for you to remember. Remove the “o” then move to the left, remove the other “o” and move to the left. Now you have a decimal and a percentage that are exactly the same!
1% = 0.01
20% = 0.20
10% = 0.10
100% = 1.00
I am not sure why the USA has not embraced the metric system more strongly than our current usage. I never think of 1/12 of an onion or pepper when making dinner. Let me show you a few amounts and please tell me what you would rather work with, whole numbers or odd fractions.
1 ounce = 28 grams = 0.0625 lbs
7 ounces = 198 grams = 0.4375 lbs
2 ounces = 56 grams = 0.125 lbs
15 ounces = 425 grams = 0.9375 lbs
May I suggest that you think of a dollar bill as metric? There is no coin equal to 1/12 (such as an inch from 1 foot) and there is no coin that is equal to 1/16 (such as one ounce of 1 pound). The more we think in simple numbers, (singles, tens and hundreds), the easier it will be to learn math. All our favorite recipes will be used in metrics, never avoirdupois.
How to calculate the percentage needed
We are often asked to “do the math” for someone who wants to scale a recipe. Since this is something we cover every day, and we give reference to the math on our daily blog, let’s talk about how to convert. For any container that you plan to use, weigh the container and press the TARE button on the scale. Record that number! Now fill the container with water. Record that number as well! I have often kept empty containers in a box that have numbers on them. The number is the quantity of water that can be placed inside the container. Some items are difficult to fill with water, such as lip balm tubes, lotion bar tubes and similar type containers. These containers leak when water or something very fluid is placed inside. It is best to make a batch of mixture and fill one tube to record the amount of material that can be contained inside. Keep a 3 x 5 card, empty container or a great notebook. You must know how much material you wish to make before we do any formulation math at all. Record your numbers as WT for the actual container weight, FL for the weight of the material when you fill. If a container needs 7 grams to fill, and you desire 10 containers, you will obviously need to make 70 grams (plus a little for loss) to fill all the containers.
Always keep your unit of measure the same, grams desired is grams to weigh. Mixing the unit of measure will be the cause of many mistakes.
I will demonstrate with the Light Gift Lotion recipe and the 2 oz container. Each 2 oz container will need 60 grams of product to fill each container. I decided that I want to make 9 of these 2 oz lotion bottles. One for me, one for my mom, one for me, one for my friend, one for me, one for my assistant, one for me, one for the neighbor, one for me. I think that will do it for now. 😉
To make enough lotion to fill 9 containers we calculate the total weight needed to fill these containers it will be 9 (containers) X 60 (grams to fill each container) = 540 grams Total Weight Needed.
Now we calculate the amount of each ingredient needed in grams. Water 540 X .64 = 345.6 grams needed. That was easy! I’ve calculated the rest to show you how simple the math is.
Light Gift Lotion
Total Weight Needed 540 grams
Peach Kernel Oil
Green Tea Extract
Vitamin E Acetate
Preservative – Liquid Germall Plus
Scent (Lemongrass EO)
540 X .64
540 X .14
540 X .06
540 X .05
540 X .03
540 X .01
540 X .01
540 X .01
540 X .01
540 X .01
540 X .02
540 X .005
540 X .005
Amount to Weigh
Here is the rest of the directions for this recipe. Remember to keep a journal of all your attempts at each recipe, it will make it easier to repeat all of you fabulous formulas.
Weigh all ingredients except the additives into the microwave safe container. Heat in the microwave using short time bursts until everything is melted. Blend the ingredients to a smooth, creamy consistency using the immersion blender. Add additives once the temperature drops to 120°F in the mixing bucket. Stir until completely mixed. Pour into bottles and allow to cool completely before capping.
Notes: This lotion is very fluid. Bottles are great for this lotion due to the fluidity. I’ve even used this as a light daily face lotion. Next time I will make this lotion just for the face and I’ll put it in 2 oz PET Bottles with a treatment pump.
Math: it is as simple as we make it. I hope you take the next step when following a recipe and do the math in calculating how much lotions or creams you desire to make. Remember one for me and one for you!