How To Calculate The Amount Of Lye Based On Oils Used

For your Lye and Oils to result into a bar soap; there is a certain number of Lye needed to react with certain amount of Oils. I hope you know you can use more than one Oils in your bar soap production.

For instance, let’s say you want to use the following Oils:

• Olive Oil 750g
• Lard 750g
• Palm Kernel Oil 500g

Step 1: Multiply Each Oil By Their Corresponding Lye (NaOH) SAP Value

• Olive Oil 750g x 0.134 = 100.5g
• Lard 750g x 0.138 = 103.5g
• Palm Kernel Oil 500g x 0.175 = 87.5g

Step 2: Add Up The Calculated Amounts

100.5 + 103.5 + 87.5 = 291.5g

Finally, 292g (when you rounded up the 291.5g) is the total amount of lye needed to fully saponify your soap, using the above oils.

Understanding Discount And Percentage In Bar Soap Production

You see, when you are producing bar soap; it is important that your soap moisturizes your skin, and does it do that? It does that by having excess amount of oils in your production. For example, in the above production; we needed exactly 292g of Lye to fully saponify 2000g of oils. So, there are two ways to get this excess oils in our production:

1. By Increasing the total amount of oils use by 5%
2. By Reducing the total amount of Lye used in the production

You will want to take a discount of your lye amount so your soap is “superfatted”, meaning some of the good oils are left in your soap to moisturize your skin. Normal “superfatting” or lye discounting is 3-10% with the norm being 5-7%.

Increasing The Total Amount Of Oils Used By 5% (Oils Percentage)

Step 1: Calculate the total number of oils used; in this case: 750g + 750g + 500g = 2000g

Step 2: Calculate 5% (0.05) of the total number of oils used. 2000 x 0.05 = 100g (this is your superfat)

Step 3: Now, you can add 100g of an oils after you reach trace to superfat. That means you will be using a total number of 2100g of oils instead of the original 2000g.

Reducing the Total Amount Of Lye To Be Use (Taking Lye Discount)

Step 1: Calculate the total amount of lye to be use; which is 292g in our case.

Step 2: Calculate the 5% discount of the total number of Lye to be use. 292g x 0.05 = 14.6 (15g after rounding up)

Step 3: Now, subtract 15g from the total amount of Lye 292g. i.e 292g – 15 = 277g

I hope this helps someone; if you have any question on contribution. Please, leave it as a comment below.